HEPSERA® is the tradename for adefovir dipivoxil, a diester prodrug of adefovir. Adefovir is an acyclic nucleotide analog with activity against human hepatitis B virus (HBV).

The chemical name of adefovir dipivoxil is 9-[2-[[bis[(pivaloyloxy)methoxy]-phosphinyl]-methoxy]ethyl]adenine. It has a molecular formula of C₂₀H₃₂N₅O₈P, a molecular weight of 501.48 and the following structural formula:

Adefovir dipivoxil is a white to off-white crystalline powder with an aqueous solubility of 19 mg/mL at pH 2.0 and 0.4 mg/mL at pH 7.2. It has an octanol/aqueous phosphate buffer (pH 7) partition coefficient (log p) of 1.91.

HEPSERA tablets are for oral administration. Each tablet contains 10 mg of adefovir dipivoxil and the following inactive ingredients: croscarmellose sodium, lactose monohydrate, magnesium stearate, pregelatinized starch, and talc.

Last updated on RxList: 11/5/2009

HEPSERA is indicated for the treatment of chronic hepatitis B in patients 12 years of age and older with evidence of active viral replication and either evidence of persistent elevations in serum aminotransferases (ALT or AST) or histologically active disease.

This indication is based on histological, virological, biochemical, and serological responses in adult patients with HBeAg+ and HBeAg- chronic hepatitis B with compensated liver function, and with clinical evidence of lamivudine-resistant hepatitis B virus with either compensated or decompensated liver function.

For patients 12 to < 18 years of age, the indication is based on virological and biochemical responses in patients with HBeAg+ chronic hepatitis B virus infection with compensated liver function.

Chronic Hepatitis B

The recommended dose of HEPSERA in chronic hepatitis B patients for patients ≥ 12 years of age with adequate renal function is 10 mg, once daily, taken orally, without regard to food. The optimal duration of treatment is unknown.

HEPSERA is not recommended for use in children less than 12 years of age.

Dose Adjustment in Renal Impairment

Significantly increased drug exposures were seen when HEPSERA was administered to adult patients with renal impairment [see WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY]. Therefore, the dosing interval of HEPSERA should be adjusted in adult patients with baseline creatinine clearance < 50 mL/min using the following suggested guidelines (see Table 1). The safety and effectiveness of these dosing interval adjustment guidelines have not been clinically evaluated.

Additionally, it is important to note that these guidelines were derived from data in patients with pre-existing renal impairment at baseline. They may not be appropriate for patients in whom renal insufficiency evolves during treatment with HEPSERA. Therefore, clinical response to treatment and renal function should be closely monitored in these patients.

Table 1. Dosing Interval Adjustment of HEPSERA in Adult Patients with Renal Impairment

	Creatinine Clearance (mL/min)a			Hemodialysis Patients
	≥ 50	30–49	10–29
Recommended dose and dosing interval	10 mg every 24 hours	10 mg every 48 hours	10 mg every 72 hours	10 mg every 7 days following dialysis
a Creatinine clearance calculated by Cockcroft-Gault method using lean or ideal body weight.

The pharmacokinetics of adefovir have not been evaluated in non-hemodialysis patients with creatinine clearance < 10 mL/min; therefore, no dosing recommendation is available for these patients.

No clinical data are available to make dosing recommendations in adolescent patients with renal insufficiency [see WARNINGS AND PRECAUTIONS].

Dosage Forms And Strengths

HEPSERA is available as tablets. Each tablet contains 10 mg of adefovir dipivoxil. The tablets are white and debossed with “10” and “GILEAD” on one side and the stylized figure of a liver on the other side.

HEPSERA is available as tablets. Each tablet contains 10 mg of adefovir dipivoxil. The tablets are white and debossed with “10” and “GILEAD” on one side and the stylized figure of a liver on the other side. They are packaged as follows:

Bottles of 30 tablets (NDC 61958-0501-1) containing desiccant (silica gel) and closed with a child-resistant closure.

Store in original container at 25 °C (77 °F), excursions permitted to 15-30 °C (59-86 °F) (see USP Controlled Room Temperature).

Do not use if seal over bottle opening is broken or missing.

Manufactured for: Gilead Sciences, Inc. Foster City, CA 94404.

Last updated on RxList: 11/5/2009

The following adverse reactions are discussed in other sections of the labeling:

• Severe acute exacerbations of Hepatitis [see Boxed Warning, WARNINGS AND PRECAUTIONS]
• Nephrotoxicity [see Boxed Warning, WARNINGS AND PRECAUTIONS]

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Clinical and laboratory evidence of exacerbations of hepatitis have occurred after discontinuation of treatment with HEPSERA.

Adverse reactions to HEPSERA identified from placebo-controlled and open label studies include the following: asthenia, headache, abdominal pain, diarrhea, nausea, dyspepsia, flatulence, increased creatinine, and hypophosphatemia.

The incidence of these adverse reactions in studies 437 and 438, where 522 patients with chronic hepatitis B and compensated liver disease received double-blind treatment with HEPSERA (n=294) or placebo (n=228) for 48 weeks is presented in Table 2. Patients who received open-label HEPSERA for up to 240 weeks in Study 438 reported adverse reactions similar in nature and severity to those reported in the first 48 weeks.

Table 2: Adverse Reactions (Grades 1–4) Reported in ≥ 3% of All HEPSERA-Treated Patients in Pooled Studies 437-438 Studies (0–48 Weeks)^a

Adverse Reaction	HEPSERA10mg (N=294)	Placebo (N=228)
Asthenia	13%	14%
Headache	9%	10%
Abdominal Pain	9%	11%
Nausea	5%	8%
Flatulence	4%	4%
Diarrhea	3%	4%
Dyspepsia	3%	2%
a In these studies, the overall incidence of adverse reactions with HEPSERA was similar to that reported with placebo. The incidence of adverse reactions is derived from treatment-related events as identified by the study investigators.

No patients treated with HEPSERA developed a confirmed serum creatinine increase ≥ 0.5 mg/dL or confirmed phosphorus decrease ≤ 2 mg/dL from baseline by Week 48. By Week 96, 2% of HEPSERA-treated patients, by Kaplan-Meier estimate, had increases in serum creatinine ≥ 0.5 mg/dL from baseline (no placebo-controlled results were available for comparison beyond Week 48). For patients who chose to continue HEPSERA for up to 240 weeks in Study 438, 4 of 125 patients (3%) had a confirmed increase of 0.5 mg/dL from baseline. The creatinine elevation resolved in 1 patient who permanently discontinued treatment and remained stable in 3 patients who continued treatment. For 65 patients who chose to continue HEPSERA for up to 240 weeks in Study 437, 6 had a confirmed increase in serum creatinine of ≥ 0.5 mg/dL from baseline with 2 patients discontinuing from the study due to the elevated serum creatinine concentration. See ADVERSE REACTIONS for changes in serum creatinine in patients with underlying renal insufficiency at baseline.

Special Risk Patients

Pre- and Post-Liver Transplantation Patients

Additional adverse reactions observed from an open-label study (Study 435) in pre- and post- liver transplantation patients with chronic hepatitis B and lamivudine-resistant hepatitis B administered HEPSERA once daily for up to 203 weeks include: abnormal renal function, renal failure, vomiting, rash, and pruritus.

Changes in renal function occurred in pre-and post-liver transplantation patients with risk factors for renal dysfunction, including concomitant use of cyclosporine and tacrolimus, renal insufficiency at baseline, hypertension, diabetes, and on-study transplantation. Therefore, the contributory role of HEPSERA to these changes in renal function is difficult to assess.

Increases in serum creatinine ≥ 0.3 mg/dL from baseline were observed in 37% and 53% of pre-liver transplantation patients by Weeks 48 and 96, respectively, by Kaplan-

Meier estimates. Increases in serum creatinine ≥ 0.3 mg/dL from baseline were observed in 32% and 51% of post-liver transplantation patients by Weeks 48 and 96, respectively, by Kaplan-Meier estimates. Serum phosphorus values < 2 mg/dL were observed in 3/226 (1.3%) of pre-liver transplantation patients and in 6/241 (2.5%) of post-liver transplantation patients by last study visit. Four percent (19 of 467) of patients discontinued treatment with HEPSERA due to renal adverse events.

Pediatric Patients

Assessment of adverse reactions is based on a placebo-controlled study (Study 518) in which 173 pediatric patients aged 2 to < 18 years with chronic hepatitis B and compensated liver disease received double-blind treatment with HEPSERA (n=115), or placebo (n=58) for 48 weeks [see Clinical Studies and Use In Specific Populations].

The safety profile of HEPSERA in patients ≥ 12 to < 18 years of age (n=56) was similar to that observed in adults. No pediatric patients treated with HEPSERA developed a confirmed serum creatinine increase ≥ 0.5 mg/dL or confirmed phosphorus decrease to < 2 mg/dL from baseline by Week 48.

Post-Marketing Experience

In addition to adverse reaction reports from clinical trials, the following possible adverse reactions have also been identified during post-approval use of adefovir dipivoxil. Because these events have been reported voluntarily from a population of unknown size, estimates of frequency cannot be made.

Metabolism and Nutrition Disorders: hypophosphatemia

Gastrointestinal Disorders: pancreatitis

Musculoskeletal System and Connective Tissue Disorders: myopathy, osteomalacia (both associated with proximal renal tubulopathy)

Renal and Urinary Disorders: renal failure, Fanconi syndrome, proximal renal tubulopathy.

Since adefovir is eliminated by the kidney, co-administration of HEPSERA with drugs that reduce renal function or compete for active tubular secretion may increase serum concentrations of either adefovir and/or these co-administered drugs [see CLINICAL PHARMACOLOGY].

Patients should be monitored closely for adverse events when HEPSERA is co-administered with drugs that are excreted renally or with other drugs known to affect renal function [see WARNINGS AND PRECAUTIONS].

HEPSERA should not be administered in combination with VIREAD [see WARNINGS AND PRECAUTIONS].

Last updated on RxList: 11/5/2009

Included as part of the PRECAUTIONS section.

Exacerbation of Hepatitis after Discontinuation of Treatment

Severe acute exacerbation of hepatitis has been reported in patients who have discontinued anti-hepatitis B therapy, including therapy with HEPSERA. Hepatic function should be monitored at repeated intervals with both clinical and laboratory follow-up for at least several months in patients who discontinue HEPSERA. If appropriate, resumption of anti-hepatitis B therapy may be warranted.

In clinical trials of HEPSERA, exacerbations of hepatitis (ALT elevations 10 times the upper limit of normal or greater) occurred in up to 25% of patients after discontinuation of HEPSERA. These events were identified in studies GS-98-437 and GS-98-438 (N=492). Most of these events occurred within 12 weeks of drug discontinuation. These exacerbations generally occurred in the absence of HBeAg seroconversion, and presented as serum ALT elevations in addition to re-emergence of viral replication. In the HBeAg-positive and HBeAg-negative studies in patients with compensated liver function, the exacerbations were not generally accompanied by hepatic decompensation. However, patients with advanced liver disease or cirrhosis may be at higher risk for hepatic decompensation. Although most events appear to have been self-limited or resolved with re-initiation of treatment, severe hepatitis exacerbations, including fatalities, have been reported. Therefore, patients should be closely monitored after stopping treatment.

Nephrotoxicity

Nephrotoxicity characterized by a delayed onset of gradual increases in serum creatinine and decreases in serum phosphorus was historically shown to be the treatment-limiting toxicity of adefovir dipivoxil therapy at substantially higher doses in HIV-infected patients (60 and 120 mg daily) and in chronic hepatitis B patients (30 mg daily). Chronic administration of HEPSERA (10 mg once daily) may result in delayed nephrotoxicity. The overall risk of nephrotoxicity in patients with adequate renal function is low. However, this is of special importance in patients at risk of or having underlying renal dysfunction and patients taking concomitant nephrotoxic agents such as cyclosporine, tacrolimus, aminoglycosides, vancomycin and non-steroidal anti-inflammatory drugs [see ADVERSE REACTIONS and CLINICAL PHARMACOLOGY]. It is recommended that creatinine clearance is calculated in all patients prior to initiating therapy with HEPSERA.

It is important to monitor renal function for all patients during treatment with HEPSERA, particularly for those with pre-existing or other risks for renal impairment. Patients with renal insufficiency at baseline or during treatment may require dose adjustment [see DOSAGE AND ADMINISTRATION]. The risks and benefits of HEPSERA treatment should be carefully evaluated prior to discontinuing HEPSERA in a patient with treatment-emergent nephrotoxicity.

Pediatric Patients

The efficacy and safety of HEPSERA have not been studied in patients less than 18 years of age with different degrees of renal impairment and no data are available to make dosage recommendations in these patients [see DOSAGE AND ADMINISTRATION]. Caution should be exercised when prescribing HEPSERA to adolescents with underlying renal dysfunction, and renal function in these patients should be closely monitored.

HIV Resistance

Prior to initiating HEPSERA therapy, HIV antibody testing should be offered to all patients. Treatment with anti-hepatitis B therapies, such as HEPSERA, that have activity against HIV in a chronic hepatitis B patient with unrecognized or untreated HIV infection may result in emergence of HIV resistance. HEPSERA has not been shown to suppress HIV RNA in patients; however, there are limited data on the use of HEPSERA to treat patients with chronic hepatitis B co-infected with HIV.

Lactic Acidosis/Severe Hepatomegaly with Steatosis

Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with antiretrovirals.

A majority of these cases have been in women. Obesity and prolonged nucleoside exposure may be risk factors. Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for liver disease; however, cases have also been reported in patients with no known risk factors. Treatment with HEPSERA should be suspended in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).

Coadministration with Other Products

HEPSERA should not be used concurrently with VIREAD (tenofovir disoproxil fumarate) or tenofovir disoproxil fumarate-containing products including TRUVADA (emtricitabine/tenofovir disoproxil fumarate combination tablet) and ATRIPLA (efavirenz/emtricitabine/tenofivir disoproxil fumarate combination tablet).

Clinical Resistance

Resistance to adefovir dipivoxil can result in viral load rebound which may result in exacerbation of hepatitis B and, in the setting of diminished hepatic function, lead to liver decompensation and possible fatal outcome.

In order to reduce the risk of resistance in patients with lamivudine resistant HBV, adefovir dipivoxil should be used in combination with lamivudine and not as adefovir dipivoxil monotherapy.

In order to reduce the risk of resistance in all patients receiving adefovir dipivoxil monotherapy, a modification of treatment should be considered if serum HBV DNA remains above 1000 copies/mL with continued treatment.

Long-term (144 week) data from Study 438 (n=124) show that patients with HBV DNA levels greater than 1000 copies/mL at Week 48 of treatment with HEPSERA were at greater risk of developing resistance than patients with serum HBV DNA levels below 1000 copies/mL at Week 48 of therapy.

Patient Counseling Information

Instructions for Safe Use

See FDA-approved patient labeling.

• Physicians should inform patients of the potential risks and benefits of HEPSERA and of alternative modes of therapy.
• Physicians should instruct their patients to
  • Read the Patient Package Insert before starting HEPSERA therapy.
  • Follow a regular dosing schedule to avoid missing doses.
  • Immediately report any severe abdominal pain, muscle pain, yellowing of the eyes, dark urine, pale stools, and/or loss in appetite.
  • Inform their doctor or pharmacist if they develop any unusual symptom(s), or if any known symptom persists or worsens.
• Patients should remain under the care of a physician when using HEPSERA.
• Patients should be advised that
  • The optimal duration of HEPSERA treatment and the relationship between treatment response and long-term outcomes such as hepatocellular carcinoma or decompensated cirrhosis are not known.
  • Patients should not discontinue Hepsera without first informing their physician [See WARNINGS AND PRECAUTIONS]
  • Routine laboratory monitoring and follow-up with a physician is important during HEPSERA therapy.
  • Obtaining HIV antibody testing prior to starting HEPSERA is important [See WARNINGS AND PRECAUTIONS]
  • HEPSERA should not be administered concurrently with VIREAD or TRUVADA or ATRIPLA [See WARNINGS AND PRECAUTIONS]
  • Lamivudine-resistant patients should use HEPSERA in combination with lamivudine and not as HEPSERA monotherapy [See WARNINGS AND PRECAUTIONS]

Pregnancy and Breastfeeding

• Physicians should inform women of childbearing age about the risks associated with exposure to HEPSERA during pregnancy.
• Patients should inform their physician if they become pregnant while using HEPSERA.
• Pregnant patients using HEPSERA should be informed about the HEPSERA pregnancy registry and offered the opportunity to enroll.
• Patients should be informed that it is not known whether HEPSERA is excreted into human milk or if it can harm a nursing infant. Therefore, a decision should be made whether to discontinue breastfeeding or drug.

Nonclinical Toxicology

Carcinogenesis, Mutagenesis, Impairment of Fertility

Long-term oral carcinogenicity studies of adefovir dipivoxil in mice and rats were carried out at exposures up to approximately 10 times (mice) and 4 times (rats) those observed in humans at the therapeutic dose for HBV infection. In both mouse and rat studies, adefovir dipivoxil was negative for carcinogenic findings. Adefovir dipivoxil was mutagenic in the in vitro mouse lymphoma cell assay (with or without metabolic activation). Adefovir induced chromosomal aberrations in the in vitro human peripheral blood lymphocyte assay without metabolic activation. Adefovir dipivoxil was not clastogenic in the in vivo mouse micronucleus assay and adefovir was not mutagenic in the Ames bacterial reverse mutation assay using S. typhimurium and E. coli strains in the presence or absence of metabolic activation. In reproductive toxicology studies, no evidence of impaired fertility was seen in male or female rats at systemic exposure approximately 19 times that achieved in humans at the therapeutic dose.

Use In Specific Populations

Pregnancy

Teratogenic Effects: Pregnancy Category C

There are no adequate and well-controlled studies of HEPSERA in pregnant women. Chronic hepatitis B is a serious condition that requires treatment. HEPSERA should be used during pregnancy only if the potential benefit to the mother justifies the potential risk to the fetus.

Reproduction studies with oral administration of adefovir dipivoxil to pregnant rats and rabbits showed no evidence of embryotoxicity or teratogenicity at systemic exposures equivalent to 23 times (rats) and 40 times (rabbits) that achieved in humans at the therapeutic dose. However, embryotoxicity and an increased incidence of fetal malformations (anasarca, depressed eye bulge, umbilical hernia and kinked tail) occurred when adefovir was administered intravenously to pregnant rats at 38 times the human therapeutic exposure. These adverse reproductive effects did not occur following an intravenous dose where exposure was 12 times the human therapeutic exposure.

Because animal reproduction studies are not always predictive of human response, HEPSERA should be used during pregnancy only if clearly needed and after careful consideration of the risks and benefits [see Nonclinical Toxicology].

Pregnancy Registry

To monitor fetal outcomes of pregnant women exposed to HEPSERA, a pregnancy registry has been established. Healthcare providers are encouraged to register patients by calling 1-800-258-4263.

Labor and Delivery

There are no studies in pregnant women and no data on the effect of HEPSERA on transmission of HBV from mother to infant. Therefore, appropriate infant immunizations should be used to prevent neonatal acquisition of hepatitis B virus.

Nursing Mothers

It is not known whether adefovir is excreted in human milk.

Because many drugs are excreted into human milk and because of the potential for serious adverse reactions in nursing infants from HEPSERA, a decision should be made whether to discontinue nursing or to discontinue drug, taking into account the importance of the drug to the mother.

Pediatric Use

Pediatric patients 12 to < 18 years: The safety, efficacy, and pharmacokinetics of HEPSERA in pediatric patients (aged ≥ 12 to < 18 years) were evaluated in a double-blind, randomized, placebo-controlled study (GS-US-103-518, Study 518) in 83 pediatric patients with chronic hepatitis B and compensated liver disease. The proportion of patients treated with HEPSERA who achieved the primary efficacy endpoint of serum HBV DNA < 1,000 copies/mL and normal ALT levels at the end of 48 weeks blinded treatment was significantly greater (23%) when compared to placebo-treated patients (0%). [see Clinical Studies, DOSAGE AND ADMINISTRATION and ADVERSE REACTIONS].

Pediatric patients 2 to < 12 years: Patients 2 to < 12 years of age were also evaluated in Study 518. The efficacy of adefovir dipivoxil was not significantly different from placebo in patients less than 12 years of age.

Hepsera is not recommended for use in children below 12 years of age.

Geriatric Use

Clinical studies of HEPSERA did not include sufficient numbers of patients aged 65 and over to determine whether they respond differently from younger patients. In general, caution should be exercised when prescribing to elderly patients since they have greater frequency of decreased renal or cardiac function due to concomitant disease or other drug therapy.

Patients with Impaired Renal Function

It is recommended that the dosing interval for HEPSERA be modified in adult patients with baseline creatinine clearance < 50 mL/min. The pharmacokinetics of adefovir have not been evaluated in non-hemodialysis patients with creatinine clearance < 10 mL/min or in adolescent patients with renal insufficiency; therefore, no dosing recommendations are available for these patients. [see DOSAGE AND ADMINISTRATION and WARNINGS AND PRECAUTIONS].

Last updated on RxList: 11/5/2009

Doses of adefovir dipivoxil 500 mg daily for 2 weeks and 250 mg daily for 12 weeks have been associated with gastrointestinal side effects. If overdose occurs the patient must be monitored for evidence of toxicity, and standard supportive treatment applied as necessary.

Following a 10 mg single dose of HEPSERA, a four-hour hemodialysis session removed approximately 35% of the adefovir dose.

HEPSERA is contraindicated in patients with previously demonstrated hypersensitivity to any of the components of the product.

Last updated on RxList: 11/5/2009

Mechanism of Action

Adefovir is an antiviral drug.

Pharmacokinetics

Adult Subjects

The pharmacokinetics of adefovir have been evaluated in healthy volunteers and patients with chronic hepatitis B. Adefovir pharmacokinetics are similar between these populations.

Absorption

Adefovir dipivoxil is a diester prodrug of the active moiety adefovir. Based on a cross study comparison, the approximate oral bioavailability of adefovir from HEPSERA is 59%.

Following oral administration of a 10 mg single dose of HEPSERA to chronic hepatitis B patients (N=14), the peak adefovir plasma concentration (Cmax) was 18.4 ± 6.26 ng/mL (mean ± SD) and occurred between 0.58 and 4.00 hours (median=1.75 hours) post dose. The adefovir area under the plasma concentration-time curve (AUC_0-∞) was 220 ± 70.0 ng•h/mL. Plasma adefovir concentrations declined in a biexponential manner with a terminal elimination half-life of 7.48 ± 1.65 hours.

The pharmacokinetics of adefovir in subjects with adequate renal function were not affected by once daily dosing of 10 mg HEPSERA over seven days. The impact of long-term once daily administration of 10 mg HEPSERA on adefovir pharmacokinetics has not been evaluated.

Effects of Food on Oral Absorption

Adefovir exposure was unaffected when a 10 mg single dose of HEPSERA was administered with food (an approximately 1000 kcal high-fat meal). HEPSERA may be taken without regard to food.

Distribution

In vitro binding of adefovir to human plasma or human serum proteins is ≤ 4% over the adefovir concentration range of 0.1 to 25 µg/mL. The volume of distribution at steady-state following intravenous administration of 1.0 or 3.0 mg/kg/day is 392 ± 75 and 352 ± 9 mL/kg, respectively.

Metabolism and Elimination

Following oral administration, adefovir dipivoxil is rapidly converted to adefovir. Forty-five percent of the dose is recovered as adefovir in the urine over 24 hours at steady state following 10 mg oral doses of HEPSERA. Adefovir is renally excreted by a combination of glomerular filtration and active tubular secretion [see DRUG INTERACTIONS].

Assessment of Drug Interactions

Adefovir dipivoxil is rapidly converted to adefovir in vivo. At concentrations substantially higher ( > 4000-fold) than those observed in vivo, adefovir did not inhibit any of the common human CYP450 enzymes, CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4. Adefovir is not a substrate for these enzymes. However, the potential for adefovir to induce CYP450 enzymes is unknown. Based on the results of these in vitro experiments and the renal elimination pathway of adefovir, the potential for CYP450 mediated interactions involving adefovir as an inhibitor or substrate with other medicinal products is low.

The pharmacokinetics of adefovir have been evaluated in healthy adult volunteers following multiple dose administration of HEPSERA (10 mg once daily) in combination with lamivudine (100 mg once daily) (N=18), trimethoprim/sulfamethoxazole (160/800 mg twice daily) (N=18), acetaminophen (1000 mg four times daily) (N=20), ibuprofen (800 mg three times daily) (N=18), and enteric coated didanosine (400 mg) (N=21). The pharmacokinetics of adefovir have also been evaluated in post-liver transplantation patients following multiple dose administration of HEPSERA (10 mg once daily) in combination with tacrolimus (N=16). The pharmacokinetics of adefovir have been evaluated in healthy volunteers following single dose pegylated interferon α-2a (PEG-IFN) (180 µg) (N=15).

Adefovir did not alter the pharmacokinetics of lamivudine, trimethoprim/sulfamethoxazole, acetaminophen, ibuprofen, enteric coated didanosine (didanosine EC), or tacrolimus. The evaluation of the effect of adefovir on the pharmacokinetics of pegylated interferon α-2a was inconclusive due to the high variability of pegylated interferon alpha-2a.

The pharmacokinetics of adefovir were unchanged when HEPSERA was coadministered with lamivudine, trimethoprim/sulfamethoxazole, acetaminophen, didanosine EC, tacrolimus (based on cross study comparison), and pegylated interferon α-2a. When HEPSERA was coadministered with ibuprofen (800 mg three times daily) increases in adefovir Cmax (33%), AUC (23%) and urinary recovery were observed. This increase appears to be due to higher oral bioavailability, not a reduction in renal clearance of adefovir.

Apart from lamivudine, trimethoprim/sulfamethoxazole, and acetaminophen, the effects of co-administration of HEPSERA with drugs that are excreted renally, or other drugs known to affect renal function have not been evaluated.

The effect of adefovir on cyclosporine concentrations is not known.

No drug interaction studies have been performed in adolescent patients aged ≥ 12 years to < 18 years.

Special Populations

Gender

The pharmacokinetics of adefovir were similar in male and female patients.

Race

The pharmacokinetics of adefovir have been shown to be comparable in Caucasians and Asians. Pharmacokinetic data are not available for other racial groups.

Geriatric Patients

Pharmacokinetic studies have not been conducted in the elderly.

Pediatric Patients

The pharmacokinetics of adefovir were assessed from drug plasma concentrations in 53 HBeAg positive hepatitis B pediatric patients with compensated liver disease. The exposure of adefovir following a 48 week daily treatment with adefovir dipivoxil 10 mg tablet in pediatric patients aged ≥ 12 to < 18 years (Cmax = 23.3 ng/ml and AUC_0-24 = 248.8 ng•h/ml) was comparable to that observed in adult patients.

Renal Impairment

In adults with moderately or severely impaired renal function or with end-stage renal disease (ESRD) requiring hemodialysis, Cmax, AUC, and half-life (T_1/2) were increased compared to adults with normal renal function. It is recommended that the dosing interval of HEPSERA be modified in these patients [see DOSAGE AND ADMINISTRATION].

The pharmacokinetics of adefovir in non-chronic hepatitis B patients with varying degrees of renal impairment are described in Table 3. In this study, subjects received a 10 mg single dose of HEPSERA.

Table 3: Pharmacokinetic Parameters (Mean ± SD) of Adefovir in Patients with Varying Degrees of Renal Function

Renal Function Group	Unimpaired	Mild	Moderate	Severe
Baseline creatinine clearance (mL/min)	> 80 (N=7)	50–80 (N=8)	30–49 (N=7)	10–29 (N=10)
Cmax (ng/mL)	17.8 ± 3.22	22.4 ± 4.04	28.5 ± 8.57	51.6 ± 10.3
AUC 0-∞ (ng•h/mL)	201 ± 40.8	266 ± 55.7	455 ± 176	1240 ± 629
CL/F (mL/min)	469 ± 99.0	356 ± 85.6	237 ± 118	91.7 ± 51.3
CLrenal (mL/min)	231 ± 48.9	148 ± 39.3	83.9 ± 27.5	37.0 ± 18.4

A four-hour period of hemodialysis removed approximately 35% of the adefovir dose. The effect of peritoneal dialysis on adefovir removal has not been evaluated.

The pharmacokinetics of adefovir have not been studied in adolescent patients with renal dysfunction [see Use in Specific Populations].

Hepatic Impairment

The pharmacokinetics of adefovir following a 10 mg single dose of HEPSERA have been studied in non-chronic hepatitis B patients with hepatic impairment. There were no substantial alterations in adefovir pharmacokinetics in patients with moderate and severe hepatic impairment compared to unimpaired patients. No change in HEPSERA dosing is required in patients with hepatic impairment.

Microbiology

Mechanism of Action

Adefovir is an acyclic nucleotide analog of adenosine monophosphate which is phosphorylated to the active metabolite adefovir diphosphate by cellular kinases. Adefovir diphosphate inhibits HBV DNA polymerase (reverse transcriptase) by competing with the natural substrate deoxyadenosine triphosphate and by causing DNA chain termination after its incorporation into viral DNA. The inhibition constant (K_i) for adefovir diphosphate for HBV DNA polymerase was 0.1 µM. Adefovir diphosphate is a weak inhibitor of human DNA polymerases α and γ with K_i values of 1.18 µM and 0.97 µM, respectively.

Antiviral Activity

The concentration of adefovir that inhibited 50% of viral DNA synthesis (EC₅₀) in HBV transfected human hepatoma cell lines ranged from 0.2 to 2.5 µM. The combination of adefovir with lamivudine showed additive anti-HBV activity.

Resistance

Clinical isolates with genotypic changes conferring reduced susceptibility in cell culture to nucleoside analog reverse transcriptase inhibitors for the treatment of HBV infection have been observed. Long-term resistance analyses performed by genotyping samples from all adefovir dipivoxil-treated patients with detectable serum HBV DNA demonstrated that amino acid substitutions rtN236T and rtA181T/V have been observed in association with adefovir resistance. In cell culture, the rtN236T substitution demonstrated 4- to 14-fold, the rtA181V substitution 2.5- to 4.2-fold, and the rtA181T substitution 1.3- to 1.9-fold reduced susceptibility to adefovir.

In HBeAg-positive nucleoside-naïve patient isolates (Study GS-98-437, N=171), no adefovir resistance-associated substitutions were observed at Week 48. Sixty-five patients continued on long term treatment after a median duration on adefovir dipivoxil of 235 weeks (range 110–279 weeks). Isolates from 16 of 38 (42%) patients developed adefovir resistance-associated substitutions in the setting of virologic failure (confirmed increase of ≥ 1 log₁₀ HBV DNA copies/mL above nadir or never suppressed below 103 copies/mL). The substitutions included rtN236T (n=2), rtA181V (n=4), rtA181T (n=3), rtA181T+rtN236T (n=5), and rtA181V+rtN236T (n=2). In HBeAg-negative nucleoside-naïve patients (Study GS-98-438), isolates from 30 patients were identified with adefovir resistance-associated substitutions with a cumulative probability of 0%, 3%, 11%, 19%, and 30% at 48, 96, 144, 192, and 240 weeks, respectively. Of those 30 patients, 22 had a confirmed increase of ≥ 1 log₁₀ HBV DNA copies/mL above nadir or never achieved HBV DNA levels below 10³ copies/mL; an additional 8 patients had adefovir resistance-associated substitutions without virologic failure. In addition, the long term (4 to 5 years) development of resistance to adefovir dipivoxil was significantly lower in patients who had serum HBV DNA below the limit of quantification (less than 1,000 copies/mL) at Week 48 as compared to patients who had serum HBV DNA above 1,000 copies/mL at Week 48.

In an open-label study of pre- and post-liver transplantation patients (Study GS-98-435), isolates from 129 patients with clinical evidence of lamivudine-resistant hepatitis B virus at baseline were evaluated for adefovir resistance-associated substitutions. The incidence of adefovir resistance-associated (rtN236T or rtA181T/V) substitutions was 0% at 48 weeks. Isolates from four patients developed the rtN236T substitution after 72 weeks of adefovir dipivoxil therapy. Development of the rtN236T substitution was associated with serum HBV DNA rebound. All 4 patients who developed the rtN236T substitution in their HBV had discontinued lamivudine therapy before the development of genotypic resistance and all 4 lost the lamivudine resistance-associated substitutions present at baseline. In a study of 35 HIV/HBV co-infected patients with lamivudine-resistant HBV (Study 460i) who added adefovir dipivoxil to lamivudine, no adefovir resistance-associated substitutions were observed in HBV isolates from 15/35 patients tested up to 144 weeks of therapy.

Clinical resistance in pediatric patients

In a Phase 3 pediatric Study GS-US-103-518, HBV isolates from 49 of 56 pediatric subjects (aged 12 to 17 years) had serum HBV DNA > 169 copies/mL and were evaluated for adefovir resistance-associated substitutions. rtN236T and/or rtA181V adefovir resistance-associated substitutions were not observed at Week 48. However, the rtA181T substitution was present in baseline and Week 48 isolates from 2 pediatric patients.

Cross-resistance

Recombinant HBV variants containing lamivudine-resistance-associated substitutions (rtL180M, rtM204I, rtM204V, rtL180M + rtM204V, rtV173L + rtL180M + rtM204V) were susceptible to adefovir in cell culture. Adefovir dipivoxil has also demonstrated anti-HBV activity (median reduction in serum HBV DNA of 4.1 log₁₀ copies/mL) in patients with HBV containing lamivudine-resistance-associated substitutions (Study 435). Adefovir also demonstrated in cell culture activity against HBV variants with entecavir resistance-associated substitutions (rtT184G, rtS202I, rtM250V). HBV variants with DNA polymerase substitutions rtT128N and rtR153Q or rtW153Q associated with resistance to hepatitis B virus immunoglobulin were susceptible to adefovir in cell culture.

HBV variants expressing the adefovir resistance-associated substitution rtN236T showed no change in susceptibility to entecavir in cell culture, and a 2- to 3-fold decrease in lamivudine susceptibility. HBV mutants with the adefovir resistance-associated substitution rtA181V showed a range of decreased susceptibilities to lamivudine of 1- to 14-fold and a 12-fold decrease in susceptibility to entecavir. In patients whose HBV expressed the rtA181V substitution (n=2) or the rtN236T substitution (n=3), a reduction in serum HBV DNA of 2.4 to 3.1 and 2.0 to 5.1 log₁₀ copies/mL, respectively, was observed when treatment with lamivudine was added to treatment with adefovir dipivoxil.

Animal Toxicology and/or Pharmacology

Toxicology Studies

Animal reproduction studies were conducted in rats and rabbits with orally administered adefovir dipivoxil and intravenously administered adefovir.

In rats and rabbits, no embryotoxicity or teratogenicity was shown from oral administration of adefovir dipivoxil at maternal doses producing systemic exposures approximately 23 times (rats) and 40 times (rabbits) that achieved in humans at the therapeutic dose of 10 mg/day.

When pregnant rats were administered intravenous adefovir at maternally toxic doses associated with systemic exposure 38 times that in humans, embryotoxicity and an increased incidence of fetal malformations (anasarca, depressed eye bulge, umbilical hernia, and kinked tail) were observed. No adverse effects on development were seen with intravenous adefovir administered to pregnant rats at a systemic exposure 12 times that in humans.

Animal Toxicology Studies

Renal tubular nephropathy characterized by histological alterations and/or increases in BUN and serum creatinine was the primary dose-limiting toxicity associated with administration of adefovir dipivoxil in animals. Nephrotoxicity was observed in animals at systemic exposures approximately 3–10 times higher than those in humans at the recommended therapeutic dose of 10 mg/day.

Clinical Studies

Studies 437 and 438 (Pivotal Studies)

HBeAg-Positive Chronic Hepatitis B

Study 437 was a randomized, double-blind, placebo-controlled, three-arm study in patients with HBeAg-positive chronic hepatitis B that allowed for a comparison between placebo and HEPSERA. The median age of patients was 33 years. Seventy-four percent were male, 59% were Asian, 36% were Caucasian, and 24% had prior interferon-α treatment. At baseline, patients had a median total Knodell Histology Activity Index (HAI) score of 10, a median serum HBV DNA level as measured by the Roche Amplicor Monitor polymerase chain reaction (PCR) assay (LLOQ = 1000 copies/mL) of 8.36 log₁₀ copies/mL and a median ALT level of 2.3 times the upper limit of normal.

HBeAg-Negative (Anti-HBe Positive/HBV DNA Positive) Chronic Hepatitis B

Study 438 was a randomized, double-blind, placebo-controlled study in patients who were HBeAg-negative at screening, and anti-HBe positive. The median age of patients was 46 years. Eighty-three percent were male, 66% were Caucasian, 30% were Asian and 41% had prior interferon-α treatment. At baseline, the median total Knodell HAI score was 10, the median serum HBV DNA level as measured by the Roche Amplicor Monitor PCR assay (LLOQ = 1000 copies/mL) was 7.08 log₁₀ copies/mL, and the median ALT was 2.3 times the upper limit of normal.

The primary efficacy endpoint in both studies was histological improvement at Week 48; results of which are shown in Table 4.

Table 4: Histological Response at Week 48^a

	Study 437		Study 438
	HEPSERA 10 mg (N=168)	Placebo (N=161)	HEPSERA 10 mg (N=121)	Placebo (N=57)
Improvementb	53%	25%	64%	35%
No Improvement	37%	67%	29%	63%
Missing/Unassessable Data	10%	7%	7%	2%
a Intent-to-Treat population (patients with ≥ 1 dose of study drug) with assessable baseline biopsies. b Histological improvement defined as ≥ 2 point decrease in the Knodell necro-inflammatory score with no worsening of the Knodell fibrosis score.

Table 5 illustrates the changes in Ishak Fibrosis Score by treatment group.

Table 5: Changes in Ishak Fibrosis Score at Week 48

Number of Adequate Biopsy Pairs	Study 437		Study 438
	HEPSERA 10 mg (N=152)	Placebo (N=149)	HEPSERA 10 mg (N=113)	Placebo (N=56)
Ishak Fibrosis ScoreImproveda	34%	19%	34%	14%
Unchanged	55%	60%	62%	50%
Worsened*	11%	21%	4%	36%
a Change of 1 point or more in Ishak Fibrosis Score.

At Week 48, improvement was seen with respect to mean change in serum HBV DNA (log₁₀ copies/mL), normalization of ALT, and HBeAg seroconversion as compared to placebo in patients receiving HEPSERA (Table 6).

Table 6: Change in Serum HBV DNA, ALT Normalization, and HBeAg Seroconversion at Week 48

	Study 437		Study 438
	HEPSERA 10 mg (N=171)	Placebo (N=167)	HEPSERA 10 mg (N=123)	Placebo (N=61)
Mean change ± SD in serum HBV DNA from baseline (log10 copies/mL)	-3.57 ± 1.64	-0.98 ± 1.32	-3.65 ± 1.14	-1.32 ± 1.25
ALT normalization	48%	16%	72%	29%
HBeAg seroconversion	12%	6%	NAa	NAa
a Patients with HBeAg-negative disease cannot undergo HBeAg seroconversion.

Treatment Beyond 48 Weeks

In Study 437, continued treatment with HEPSERA to 72 weeks resulted in continued maintenance of mean reductions in serum HBV DNA observed at Week 48. An increase in the proportion of patients with ALT normalization was also observed in Study 437. The effect of continued treatment with HEPSERA on seroconversion is unknown.

In Study 438, patients who received HEPSERA during the first 48 weeks were re-randomized in a blinded manner to continue on HEPSERA or receive placebo for an additional 48 weeks. At Week 96, 50 of 70 (71%) of patients who continued treatment with HEPSERA had undetectable HBV DNA levels ( < 1000 copies/mL), and 47 of 64 (73%) of patients had ALT normalization. HBV DNA and ALT levels returned towards baseline in most patients who stopped treatment with HEPSERA.

From 141 eligible patients, there were 125 (89%) patients in Study 438 who chose to continue HEPSERA for up to 192 weeks or 240 weeks (4 years or 5 years). As these patients had already received HEPSERA for at least 48 weeks and appeared to be experiencing a benefit, they are not necessarily representative of patients initiating HEPSERA. Of these patients, 89/125 (71%) and 47/70 (67%) had an undetectable HBV DNA level ( < 1000 copies/mL) at Week 192 and Week 240, respectively. Of the patients who had an elevated ALT at baseline, 77/104 (74%) and 42/64 (66%) had a normal ALT at Week 192 and Week 240, respectively. Six (5%) patients experienced HBsAg loss.

Study 435 (Pre- and Post- Liver Transplantation Patients)

HEPSERA was also evaluated in an open-label, uncontrolled study of 467 chronic hepatitis B patients pre- (N=226) and post- (N=241) liver transplantation with clinical evidence of lamivudine- resistant hepatitis B virus (Study 435). At baseline, 60% of pre-liver transplantation patients were classified as Child-Pugh-Turcotte score of Class B or C. The median baseline HBV DNA as measured by the Roche Amplicor Monitor PCR assay (LLOQ = 1000 copies/mL) was 7.4 and 8.2 log₁₀ copies/mL, and the median baseline ALT was 1.8 and 2.0 times the upper limit of normal in pre- and post-liver transplantation patients, respectively. Results of this study are displayed in Table 5. Treatment with HEPSERA resulted in a similar reduction in serum HBV DNA regardless of the patterns of lamivudine-resistant HBV DNA polymerase mutations at baseline. The significance of the efficacy results listed in Table 7 as they relate to clinical outcomes is not known.

Table 7: Efficacy in Pre- and Post-Liver Transplantation Patients at Week 48

Efficacy Parametera	Pre-Liver Transplantation (N=226)	Post-Liver Transplantation (N=241)
Mean change ± SD in HBV DNA from baseline (log10 copies/mL)	-3.7 ± 1.6 (n=117)	-4.0 ± 1.6 (n=164)
Proportion with undetectable HBV DNA ( < 1000 copies/mL)b	77/109 (71%)	64/159 (40%)
Stable or improved Child-Pugh-Turcotte score	86/90 (96%)	107/115 (93%)
Normalization of:c ALT	61/82 (74%)	56/110 (51%)
Albumin	43/54 (80%)	21/26 (81%)
Bilirubin	38/68 (58%)	29/38 (76%)
Prothrombin time	39/46 (85%)	5/9 (56%)
a Data are missing for 29% (HBV DNA) and 37% to 45% (CPT Score, Normalization of ALT, Albumin, Bilirubin, and PT) of total patients enrolled in the study. b Denominator is the number of patients with serum HBV DNA ≥ 1000 copies/mL at baseline using the Roche Amplicor Monitor PCR Assay (LLOQ = 1000 copies/mL) and non-missing value at Week 48. c Denominator is patients with abnormal values at baseline and non-missing value at Week 48.

Study 461 (Clinical Evidence of Lamivudine Resistance)

In Study 461, a double-blind, active controlled study in 59 chronic hepatitis B patients with clinical evidence of lamivudine-resistant hepatitis B virus, patients were randomized to receive either HEPSERA monotherapy or HEPSERA in combination with lamivudine 100 mg or lamivudine 100 mg alone. At Week 48, the mean ± SD decrease in serum HBV DNA as measured by the Roche Amplicor Monitor PCR assay (LLOQ = 1000 copies/mL) was 4.00 ± 1.41 log₁₀ copies/mL for patients treated with HEPSERA and 3.46 ± 1.10 log₁₀ copies/mL for patients treated with HEPSERA in combination with lamivudine. There was a mean decrease in serum HBV DNA of 0.31 ± 0.93 log₁₀ copies/mL in patients receiving lamivudine alone. ALT normalized in 47% of patients treated with HEPSERA, in 53% of patients treated with HEPSERA in combination with lamivudine, and 5% of patients treated with lamivudine alone. The significance of these findings as they relate to clinical outcomes is not known.

Study 518 (Pediatric Study)

Study 518 was a double-blind, placebo-controlled, study in which 173 pediatric patients (ages 2 to < 18 years) with chronic hepatitis B (CHB) infection and elevated ALT were randomized 2:1 (115 receiving adefovir dipivoxil and 58 receiving placebo). Randomization was stratified by prior treatment and age 2 to < 7 years old (cohort 1), 7 to < 12 years old (cohort 2), and 12 to < 18 years old (cohort 3). All patients in cohort 3 received 10 mg tablet formulation; all patients in cohorts 1 and 2 received an investigational suspension formulation (0.3 mg/kg/day cohort 1, 0.25 mg/kg/day cohort 2) once daily. The primary efficacy endpoint was HBV DNA < 1000 copies/mL plus normalization of ALT at the end of Week 48.

In cohort 3 (n=83), significantly more patients treated with HEPSERA achieved the primary efficacy endpoint at the end of 48 weeks of blinded treatment (23%) when compared to placebo-treated patients (0%). The proportion of patients from cohorts 1 and 2 who responded to treatment with adefovir dipivoxil was not statistically significant when compared to the placebo arm, although the adefovir plasma concentrations in these patients were comparable to those observed in older patients. Overall, 22 of 115 (19%) of pediatric patients who received adefovir dipivoxil vs. 1 of 58 (2%) of placebo treated patients responded to treatment by Week 48 [see ADVERSE REACTIONS, Use In Special Populations].

Last updated on RxList: 11/5/2009

HEPSERA®
(hep-SER-rah)

Generic Name: (adefovir dipivoxil) tablets

Read this information carefully before you start taking HEPSERA. Read and check for new information each time you get more HEPSERA. This information does not take the place of talking with your doctor about your medical condition or your treatment.

What is the most important information I should know about HEPSERA?

1. Some people who stop taking HEPSERA get a very serious hepatitis. This usually happens within 12 weeks after stopping. You will need to have regular blood tests to check for liver function and hepatitis B virus levels if you stop taking HEPSERA.
2. HEPSERA may cause a severe kidney problem called nephrotoxicity. It usually happens in people that already have a kidney problem, but it can happen to anyone that uses HEPSERA. You will need to have regular blood tests to check for kidney function while you are taking HEPSERA.
3. If you get or have HIV that isn't being treated with medicines, HEPSERA may increase the chances your HIV infection cannot be helped with usual HIV medicines. This can happen if you get or have HIV and don't know it, or if your HIV is not being treated while you are taking HEPSERA. You should get an HIV test before you start taking HEPSERA and anytime after that when there's a chance you were exposed to HIV.
4. Some people who have taken medicines like HEPSERA that are called nucleoside or nucleotide analogs have developed a serious condition called lactic acidosis (build up of an acid in the blood). Lactic acidosis is a medical emergency and must be treated in the hospital. Call your doctor right away if you get any of the following signs of lactic acidosis:
   • You feel very weak or tired.
   • You have unusual (not normal) muscle pain.
   • You have trouble breathing.
   • You have stomach pain with nausea and vomiting.
   • You feel cold, especially in your arms and legs.
   • You feel dizzy or lightheaded.
   • You have a fast or irregular heartbeat.

Some people who have taken medicines like HEPSERA have developed serious liver problems called hepatotoxicity, with liver enlargement (hepatomegaly) and fat in the liver (steatosis). Call your doctor right away if you get any of the following signs of liver problems.

• Your skin or the white part of your eyes turns yellow (jaundice).
• Your urine turns dark.
• Your bowel movements (stools) turn light in color.
• You don't feel like eating food for several days or longer.
• You feel sick to your stomach (nausea).
• You have lower stomach pain.

You may be more likely to get lactic acidosis or serious liver problems if you are very overweight (obese) or have been taking nucleoside analog medicines [Atripla® (efavirenz plus emtricitabine plus tenofovir disoproxil fumarate), Combivir (zidovudine plus lamivudine), Emtriva® (emtricitabine), Epivir, Epivir-HBV (lamivudine), Epzicom (abacavir plus lamivudine), Hivid (zalcitabine), Retrovir (zidovudine), Trizivir (zidovudine plus lamivudine plus abacavir), Truvada® (emtricitabine plus tenofovir disoproxil fumarate), Videx (didanosine), Viread® (tenofovir disoproxil fumarate), Zerit (stavudine), and Ziagen (abacavir)] for a long time.

What is HEPSERA?

HEPSERA is a medicine used to treat patients at least 12 years of age with continuing (chronic) infections with active hepatitis B virus. HEPSERA has not been studied in adults over the age of 65 and is not recommended for use in children less than 12 years of age.

• HEPSERA will not cure your chronic hepatitis B.
• HEPSERA may help lower the amount of hepatitis B virus in your body.
• HEPSERA may lower the ability of the virus to multiply and infect new liver cells.
• We do not know if HEPSERA will reduce your chances of getting liver cancer or liver damage (cirrhosis) from chronic hepatitis B.
• We do not know how long HEPSERA may help your hepatitis. Sometimes viruses change in your body and medicines no longer work. This is called drug resistance.
• HEPSERA does not stop you from spreading hepatitis B virus to others by sex or sharing needles. So practice safe sex and needle use.

Who should not take HEPSERA?

• Do not take HEPSERA if you are allergic to any of the ingredients in HEPSERA. The active ingredient in HEPSERA is adefovir dipivoxil. See the end of this leaflet for a complete list of all the ingredients in HEPSERA.
• Do not take HEPSERA if you are already taking VIREAD, TRUVADA or ATRIPLA.

Tell your doctor if:

• You are pregnant. We do not know if HEPSERA can harm your unborn child. You and your doctor will need to decide if HEPSERA is right for you. If you take HEPSERA and you are pregnant, talk to your doctor about how you can join the HEPSERA pregnancy registry.
• You are breast-feeding. We do not know if HEPSERA can pass into your milk and if it can harm your baby. You will need to choose either to breast feed or take HEPSERA, but not both.
• You have kidney problems now or had them before. Your dose and schedule of HEPSERA may be reduced. Blood tests will need to be done regularly to see how your kidneys are working.

Tell your doctor about all the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements. Some medicines may affect how HEPSERA works, especially medicines that affect how your kidneys work. HEPSERA can affect how your other medicines work. Your dose of HEPSERA and the other medicines may be changed. Do not take any other medicines while you are taking HEPSERA, unless your doctor has told you it is okay.

How should I take HEPSERA?

• Your doctor will tell you how much HEPSERA to take.
• Your doctor will tell you when and how often to take HEPSERA.
• Take HEPSERA the same time each day that your doctor tells you. If you forget to take HEPSERA, take it as soon as you remember that day. Do not take more than 1 dose of HEPSERA in a day. Do not take 2 doses at the same time. Call your doctor or pharmacist if you are not sure what to do.
• Do not change your dose of HEPSERA or stop HEPSERA without talking to your doctor. Your hepatitis may get worse if you change doses or stop.
• You may take HEPSERA with or without food.
• When your HEPSERA supply gets low, call your doctor or pharmacy for a refill. Do not run out of HEPSERA.
• If you take too much HEPSERA, call your local poison control center or emergency room right away.

Some patients get worse or very serious hepatitis B symptoms when they stop taking HEPSERA (see, “What is the most important information I should know about HEPSERA?”). We don't know how long you should use HEPSERA. You and your doctor will need to decide when it is best for you to stop taking HEPSERA. After you stop taking HEPSERA, your doctor will still need to check your health and take blood tests to check your liver for a few months.

What should I avoid while taking HEPSERA?

Avoid doing things that can spread hepatitis B virus since HEPSERA doesn't stop you from passing the infection to others.

• Do not share needles or other injection equipment.
• Do not share personal items that can have blood or body fluids on them, like toothbrushes or razor blades.
• Do not have any kind of sex without protection. Practice “safe sex” using condoms and dental dams.

What are the possible side effects of HEPSERA?

HEPSERA can cause the following serious side effects: (see, “What is the most important information I should know about HEPSERA?”)

• a very serious hepatitis if you stop taking it.
• a severe kidney problem called nephrotoxicity.
• increase your chance of developing a form of HIV that cannot be treated with usual HIV medicines
• lactic acidosis and liver problems.

The most common side effects of HEPSERA are weakness, headache, stomach pain, nausea, flatulence (intestinal gas), diarrhea, indigestion and changes in the way the kidneys work. Additional side effects in liver transplant patients with chronic hepatitis B are vomiting, rash and itching. Some patients with liver transplants also had undesirable effects on their kidneys, including failure of the kidneys.

Other side effects reported since HEPSERA has been marketed include kidney failure, damage to kidney cells, muscle pain or weakness and weakening of the bone, which could cause them to break (both associated with kidney problems), and inflammation of the pancreas.

These are not all of the possible side effects of HEPSERA. For more information, ask your doctor or pharmacist.

General information about the safe and effective use of HEPSERA:

Medicines are sometimes prescribed for conditions not mentioned in patient information leaflets. Do not use HEPSERA for a condition for which it was not prescribed. Do not give HEPSERA to other people, even if they have the same symptoms that you have.

This leaflet summarizes the most important information about HEPSERA. If you would like more information, talk with your doctor. You can ask your doctor or pharmacist for information about HEPSERA that is written for health professionals.

HEPSERA Tablets should be stored at room temperature and should be stored in their original container.

Do not use if seal over bottle opening is broken or missing.

What are the Ingredients of HEPSERA?

Active Ingredient: adefovir dipivoxil

Inactive Ingredients: croscarmellose sodium, lactose monohydrate, magnesium stearate, pregelatinized starch, and talc

Last updated on RxList: 11/5/2009

IMPORTANT NOTE: This is a summary and does not contain all possible information about this product. For complete information about this product or your specific health needs, ask your health care professional. Always seek the advice of your health care professional if you have any questions about this product or your medical condition. This information is not intended as individual medical advice and does not substitute for the knowledge and judgment of your health care professional. This information does not contain any assurances that this product is safe, effective, or appropriate for you.

ADEFOVIR DIPIVOXIL - ORAL

(a-DEF-oh-vir dip-ih-VOX-il)

COMMON BRAND NAME(S): Hepsera

WARNING: Severe worsening of hepatitis (rarely including death) has occurred when adefovir dipivoxil has been discontinued. When you are instructed to stop taking this medication, your doctor will monitor you closely for signs of worsening hepatitis. Be sure to keep all doctor and laboratory appointments after you stop taking this drug.

Infrequently, severe (sometimes fatal) liver and blood acid-base balance problems (lactic acidosis) have occurred while using a similar type of medication (nucleoside analogs such as didanosine or stavudine). Notify your doctor immediately if you develop unusual weakness or fatigue, dark urine, yellowing of the skin or eyes, abdominal or stomach pain, drowsiness, muscle aches or weakness, trouble breathing (e.g., rapid breathing or very shallow breathing), or fast or irregular heartbeat.

In patients with kidney disease, adefovir dipivoxil can cause kidney damage. Notify your doctor immediately if you develop a change in the amount of urine that you produce.

If you get or have HIV infection that is not being treated with medication, adefovir dipivoxil may cause your HIV infection to become untreatable with the usual HIV drugs (development of HIV resistance). Consult your doctor or pharmacist for more details.

USES: This medication is used to treat a chronic viral infection of the liver (hepatitis B) in people 12 years of age and older. It works by slowing the growth of the virus. It is not a cure for hepatitis B and does not prevent the passing of hepatitis B to others.

This medication is a nucleotide analog.

HOW TO USE: Take this medication by mouth, usually once daily; or take as directed by your doctor. May take with or without food.

This medicine comes with a patient information leaflet. Read it carefully. Ask your doctor, nurse, or pharmacist any questions that you may have about this medicine.

Take this medication exactly as prescribed. Do not increase or decrease your dose or stop taking this medication unless directed to do so by your doctor or pharmacist.

Treatment with adefovir alone is not appropriate for patients infected with both hepatitis B and HIV. An HIV test is recommended both before and during treatment to ensure you receive appropriate treatment. Consult your doctor or pharmacist for more information.

Worsening of your condition, decreased response to therapy, or the occurrence of resistant strains of the virus may occur during or after treatment. Promptly report any new symptoms that occur during or after treatment to your doctor.

SIDE EFFECTS: Weakness, headache, fever, increased cough, nausea, vomiting, diarrhea, or gas may occur. If any of these effects persist or worsen, notify your doctor promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor immediately if this very unlikely but serious side effect occurs: change in the amount of urine.

For additional side effects see Warning section.

An allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of an allergic reaction include: rash, itching, swelling, dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

Contact your doctor for medical advice about side effects. The following numbers do not provide medical advice, but in the US you may report side effects to the Food and Drug Administration (FDA) at 1-800-FDA-1088. In Canada, you may call Health Canada at 1-866-234-2345.

PRECAUTIONS: Before using this medication, tell your doctor or pharmacist your medical history, especially of: HIV infection, kidney problems, liver transplant, being very overweight (obese), allergies.

This medication should be used only when clearly needed during pregnancy. Discuss the risks and benefits with your doctor.

It is not known whether this drug passes into breast milk. Do not breast-feed while taking this medication.

DRUG INTERACTIONS: Your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with them first.

Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription products you may use, especially of: aminoglycosides (e.g., gentamicin, amikacin), amphotericin B, cyclosporine, non-steroidal anti-inflammatory drugs (e.g., ibuprofen), tacrolimus, vancomycin.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.

OVERDOSE: If overdose is suspected, contact your local poison control center or emergency room immediately. US residents can call the US national poison hotline at 1-800-222-1222. Canadian residents should call their local poison control center directly.

NOTES: Do not share this medication with others.

To avoid spreading hepatitis B to others, always use an effective barrier method (e.g., latex condoms/dental dams) during sexual activity. Consult your doctor or pharmacist for more details.

Laboratory and/or medical tests (e.g., kidney function and liver function tests) may be performed to monitor your progress or check for side effects. Consult your doctor for more details. Keep all laboratory and medical appointments during and for several months after treatment.

If using this medication for an extended period of time, obtain refills before your supply runs out.

MISSED DOSE: If you miss a dose, use it as soon as you remember that day. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.

STORAGE: Store in the original container at room temperature (77 degrees F or 25 degrees C) away from light and moisture. Brief storage between 59 and 86 degrees F (15 and 30 degrees C) is permitted. Keep away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.

MEDICAL ALERT: Your condition can cause complications in a medical emergency. For enrollment information call MedicAlert at 1-800-854-1166 (USA), or 1-800-668-1507 (Canada).

Information last revised July 2008 Copyright(c) 2008 First DataBank, Inc.