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

• Serious and sometimes fatal hypersensitivity reaction. In one study, once-daily dosing of abacavir was associated with more severe hypersensitivity reactions [see BOXED WARNING, WARNINGS AND PRECAUTIONS].
• Lactic acidosis and severe hepatomegaly [see BOXED WARNING, WARNINGS AND PRECAUTIONS].
• Acute exacerbations of hepatitis B [see BOXED WARNING, WARNINGS AND PRECAUTIONS].
• Hepatic decompensation in patients co-infected with HIV-1 and Hepatitis C [see WARNINGS AND PRECAUTIONS].
• Immune reconstitution syndrome [see WARNINGS AND PRECAUTIONS].
• Fat redistribution [see WARNINGS AND PRECAUTIONS].
• Myocardial infarction [see WARNINGS AND PRECAUTIONS].

Clinical Trials Experience

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

Therapy-Naive Adults

Treatment-emergent clinical adverse reactions (rated by the investigator as moderate or severe) with a ≥ 5% frequency during therapy with ZIAGEN 600 mg once daily or ZIAGEN 300 mg twice daily, both in combination with lamivudine 300 mg once daily and efavirenz 600 mg once daily are listed in Table 1.

Table 1: Treatment-Emergent (All Causality) Adverse Reactions of at Least Moderate Intensity (Grades 2-4, ≥ 5% Frequency) in Therapy-Naive Adults (CNA30021) Through 48 Weeks of Treatment

Laboratory Abnormalities

Laboratory abnormalities observed in clinical studies of ZIAGEN were anemia, neutropenia, liver function test abnormalities, and elevations of CPK, blood glucose, and triglycerides. Additional laboratory abnormalities observed in clinical studies of EPIVIR were thrombocytopenia and elevated levels of bilirubin, amylase, and lipase.

The frequencies of treatment-emergent laboratory abnormalities were comparable between treatment groups in Study CNA30021.

Other Adverse Events

In addition to adverse reactions listed above, other adverse events observed in the expanded access program for abacavir were pancreatitis and increased GGT.

Postmarketing Experience

In addition to adverse reactions reported from clinical studies, the following reactions have been identified during postmarketing use of abacavir, lamivudine, and/or EPZICOM. Because they are reported voluntarily from a population of unknown size, estimates of frequency cannot be made. These reactions have been chosen for inclusion due to a combination of their seriousness, frequency of reporting, or potential causal connection to abacavir, lamivudine, and/or EPZICOM.

Abacavir

Cardiovascular: Myocardial infarction.

Skin: Suspected Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) have been reported in patients receiving abacavir primarily in combination with medications known to be associated with SJS and TEN, respectively. Because of the overlap of clinical signs and symptoms between hypersensitivity to abacavir and SJS and TEN, and the possibility of multiple drug sensitivities in some patients, abacavir should be discontinued and not restarted in such cases.

There have also been reports of erythema multiforme with abacavir use.

Abacavir and Lamivudine

Body as a Whole: Redistribution/accumulation of body fat [see WARNINGS AND PRECAUTIONS].

Digestive: Stomatitis.

Endocrine and Metabolic: Hyperglycemia.

General: Weakness.

Hemic and Lymphatic: Aplastic anemia, anemia (including pure red cell aplasia and severe anemias progressing on therapy), lymphadenopathy, splenomegaly.

Hepatic: Lactic acidosis and hepatic steatosis [see WARNINGS AND PRECAUTIONS], posttreatment exacerbation of hepatitis B [see WARNINGS AND PRECAUTIONS].

Hypersensitivity: Sensitization reactions (including anaphylaxis), urticaria.

Musculoskeletal: Muscle weakness, CPK elevation, rhabdomyolysis.

Nervous: Paresthesia, peripheral neuropathy, seizures.

Respiratory: Abnormal breath sounds/wheezing.

Skin: Alopecia, erythema multiforme, Stevens-Johnson syndrome.

• No drug interaction studies have been conducted using EPZICOM Tablets [see CLINICAL PHARMACOLOGY].

Ethanol

Abacavir

Abacavir has no effect on the pharmacokinetic properties of ethanol. Ethanol decreases the elimination of abacavir causing an increase in overall exposure [see CLINICAL PHARMACOLOGY].

Interferon- and Ribavirin-Based Regimens

Lamivudine

Although no evidence of a pharmacokinetic or pharmacodynamic interaction (e.g., loss of HIV-1/HCV virologic suppression) was seen when ribavirin was coadministered with lamivudine in HIV-1/HCV co-infected subjects, hepatic decompensation (some fatal) has occurred in HIV-1/HCV co-infected subjects receiving combination antiretroviral therapy for HIV-1 and interferon alfa with or without ribavirin [see WARNINGS AND PRECAUTIONS, CLINICAL PHARMACOLOGY].

Methadone

Abacavir

The addition of methadone has no clinically significant effect on the pharmacokinetic properties of abacavir. In a study of 11 HIV-1-infected subjects receiving methadone-maintenance therapy with 600 mg of ZIAGEN twice daily (twice the currently recommended dose), oral methadone clearance increased [see CLINICAL PHARMACOLOGY]. This alteration will not result in a methadone dose modification in the majority of patients; however, an increased methadone dose may be required in a small number of patients.

Trimethoprim/Sulfamethoxazole (TMP/SMX)

Lamivudine

No change in dose of either drug is recommended [see CLINICAL PHARMACOLOGY]. There is no information regarding the effect on lamivudine pharmacokinetics of higher doses of TMP/SMX such as those used to treat PCP.

Last reviewed on RxList: 12/8/2011
This monograph has been modified to include the generic and brand name in many instances.