Pharmacokinetics
PROTONIX Delayed-Release Tablets are prepared as enteric-coated tablets so
that absorption of pantoprazole begins only after the tablet leaves the stomach.
Peak serum concentration (Cmax) and area under the serum concentration time
curve (AUC) increase in a manner proportional to oral and intravenous doses
from 10 mg to 80 mg. Pantoprazole does not accumulate and its pharmacokinetics
are unaltered with multiple daily dosing. Following oral or intravenous administration,
the serum concentration of pantoprazole declines biexponentially with a terminal
elimination half-life of approximately one hour. In extensive metabolizers (see
CLINICAL PHARMACOLOGY, Pharmacokinetics, Metabolism)
with normal liver function receiving an oral dose of the enteric-coated 40 mg
pantoprazole tablet, the peak concentration (Cmax) is 2.5μg/mL, the time
to reach the peak concentration (tmax) is 2.5 h and the total area under the
plasma concentration versus time curve (AUC) is 4.8μg·hr/mL. When pantoprazole
is given with food, its tmax is highly variable and may increase significantly.
Following intravenous administration of pantoprazole to extensive metabolizers,
its total clearance is 7.6-14.0 L/h and its apparent volume of distribution
is 11.0-23.6 L.
PROTONIX® (pantoprazole sodium) For Delayed-Release Oral Suspension has
been shown to be comparable to PROTONIX® (pantoprazole sodium) Delayed-Release
Tablets in suppressing pentagastrin-stimulated maximum acid output (MAO) in
patients with gastroesophageal reflux disease (GERD) and a history of erosive
esophagitis (EE) (see CLINICAL PHARMACOLOGY, Pharmacodynamics).
PROTONIX For Delayed-Release Oral Suspension is bioequivalent when administered
orally in applesauce or apple juice, or mixed in apple juice and administered
through a nasogastric tube. The plasma pharmacokinetic parameters from a crossover
study in healthy subjects are summarized in the table below. In this study,
a single oral 40 mg dose of Protonix For Delayed-Release Oral Suspension was
administered to healthy subjects (N = 22) as granules sprinkled over a teaspoonful
of applesauce, as granules mixed with apple juice and, mixed with apple juice
followed by administration through a nasogastric tube.
Pharmacokinetics parameters (mean ± SD) of Pantoprazole
with Administration of Protonix For Delayed-Release Oral Suspension Sprinkled
on Applesauce, Mixed with Apple Juice, Mixed with Apple Juice and Administered
through a Nasogastric Tube
| Pharmacokinetic Parameters |
Granules in applesauce |
Granules in apple juice |
Granules in nasogastric tube |
| AUC (μg•hr/mL) |
4.01 ±1.53 |
3.99 ± 1.49 |
4.06 ± 1.73 |
| Cmax (μg/mL) |
1.97± 0.69 |
1.91 ± 0.45 |
2.2 ± 0.70 |
| aTmax (hr) |
2.0 |
2.5 |
2.0 |
| a Median values are reported for Tmax |
Absorption
The absorption of pantoprazole is rapid, with a Cmax of 2.5 g/mL that occurs
approximately 2.5 hours after administration of single or multiple 40 mg doses
of PROTONIX® (pantoprazole sodium) Delayed-Release Tablets. Pantoprazole
is well absorbed; it undergoes little first-pass metabolism resulting in an
absolute bioavailability of approximately 77%. Pantoprazole absorption is not
affected by concomitant administration of antacids.
Administration of PROTONIX® (pantoprazole sodium) Delayed-Release Tablets
with food may delay its absorption up to 2 hours or longer; however, the Cmax
and the extent of pantoprazole absorption (AUC) are not altered. Thus, PROTONIX®
(pantoprazole sodium) Delayed-Release Tablets may be taken without regard to
timing of meals.
PROTONIX® (pantoprazole sodium) For Delayed-Release Oral Suspension should
be taken approximately 30 minutes before a meal.
Distribution
The apparent volume of distribution of pantoprazole is approximately 11.0-23.6
L, distributing mainly in extracellular fluid. The serum protein binding of
pantoprazole is about 98%, primarily to albumin.
Metabolism
Pantoprazole is extensively metabolized in the liver through the cytochrome
P450 (CYP) system. Pantoprazole metabolism is independent of the route of administration
(intravenous or oral). The main metabolic pathway is demethylation, by CYP2C19,
with subsequent sulfation; other metabolic pathways include oxidation by CYP3A4.
There is no evidence that any of the pantoprazole metabolites have significant
pharmacologic activity. CYP2C19 displays a known genetic polymorphism due to
its deficiency in some sub-populations (eg, 3% of Caucasians and African-Americans
and 17%-23% of Asians). Although these sub-populations of slow pantoprazole
metabolizers have elimination half-life values of 3.5 to 10.0 hours, they still
have minimal accumulation ( ≤ 23%) with once daily dosing.
Elimination
After a single oral or intravenous dose of 14C-labeled pantoprazole
to healthy, normal metabolizer volunteers, approximately 71% of the dose was
excreted in the urine with 18% excreted in the feces through biliary excretion.
There was no renal excretion of unchanged pantoprazole.
Special Populations
Geriatric
Only slight to moderate increases in pantoprazole AUC (43%) and Cmax (26%)
were found in elderly volunteers (64 to 76 years of age) after repeated oral
administration, compared with younger subjects. No dosage adjustment is recommended
based on age.
Pediatric
The pharmacokinetics of pantoprazole have not been investigated in patients
< 18 years of age.
Gender
There is a modest increase in pantoprazole AUC and Cmax in women compared to
men. However, weight-normalized clearance values are similar in women and men.
No dosage adjustment is needed based on gender (see PRECAUTIONS,
Use in Women).
Renal Impairment
In patients with severe renal impairment, pharmacokinetic parameters for pantoprazole
were similar to those of healthy subjects. No dosage adjustment is necessary
in patients with renal impairment or in patients undergoing hemodialysis.
Hepatic Impairment
In patients with mild to severe hepatic impairment, maximum pantoprazole concentrations
increased only slightly (1.5-fold) relative to healthy subjects. Although serum
half-life values increased to 7-9 hours and AUC values increased by 5- to 7-fold
in hepatic-impaired patients, these increases were no greater than those observed
in slow CYP2C19 metabolizers, where no dosage frequency adjustment is warranted.
These pharmacokinetic changes in hepatic-impaired patients result in minimal
drug accumulation following once daily multiple-dose administration. No dosage
adjustment is needed in patients with mild to severe hepatic impairment. Doses
higher than 40 mg/day have not been studied in hepatically-impaired patients.
Drug-Drug Interactions
Pantoprazole is metabolized mainly by CYP2C19 and to minor extents by CYPs
3A4, 2D6, and 2C9. In in vivo drug-drug interaction studies with CYP2C19 substrates
(diazepam [also a CYP3A4 substrate] and phenytoin [also a CYP3A4 inducer]),
nifedipine, midazolam, and clarithromycin (CYP3A4 substrates), metoprolol (a
CYP2D6 substrate), diclofenac, naproxen and piroxicam (CYP2C9 substrates), and
theophylline (a CYP1A2 substrate) in healthy subjects, the pharmacokinetics
of pantoprazole were not significantly altered. It is, therefore, expected that
other drugs metabolized by CYPs 2C19, 3A4, 2D6, 2C9, and 1A2 would not significantly
affect the pharmacokinetics of pantoprazole. In vivo studies also suggest
that pantoprazole does not significantly affect the kinetics of other drugs
(cisapride, theophylline, diazepam [and its active metabolite, desmethyldiazepam],
phenytoin, warfarin, metoprolol, nifedipine, carbamazepine, midazolam, clarithromycin,
naproxen, piroxicam, and oral contraceptives [levonorgestrel/ethinyl estradiol])
metabolized by CYPs 2C19, 3A4, 2C9, 2D6, and 1A2. Therefore, it is expected
that pantoprazole would not significantly affect the pharmacokinetics of other
drugs metabolized by these isozymes. Dosage adjustment of such drugs is not
necessary when they are coadministered with pantoprazole. In other in vivo studies,
digoxin, ethanol, glyburide, antipyrine, caffeine, metronidazole, and amoxicillin
had no clinically relevant interactions with pantoprazole. Although no significant
drug-drug interactions have been observed in clinical studies, the potential
for significant drug-drug interactions with more than once daily dosing with
high doses of pantoprazole has not been studied in poor metabolizers or individuals
who are hepatically impaired.
Pharmacodynamics
PROTONIX® (pantoprazole sodium) For Delayed-Release Oral Suspension has
been shown to be comparable to PROTONIX® (pantoprazole sodium) Delayed-Release
Tablets in suppressing pentagastrin-stimulated MAO in patients (n = 49) with
GERD and a history of EE. In this multicenter pharmacodynamic crossover study
a 40 mg oral dose of Protonix For Delayed-Release Oral Suspension administered
in a teaspoonful of applesauce was compared with a 40 mg oral dose of Protonix
Delayed-Release Tablets after administration of each formulation once daily
for 7 days. Both medications were administered thirty minutes before breakfast.
Pentagastrin-stimulated MAO was then assessed from hour 23 to 24 at steady state.
Mechanism of Action
Pantoprazole is a proton pump inhibitor (PPI) that suppresses the final step
in gastric acid production by covalently binding to the (H+,K+)-ATPase
enzyme system at the secretory surface of the gastric parietal cell. This effect
leads to inhibition of both basal and stimulated gastric acid secretion irrespective
of the stimulus. The binding to the (H+,K+)-ATPase results
in a duration of antisecretory effect that persists longer than 24 hours for
all doses tested.
Antisecretory Activity
Under maximal acid stimulatory conditions using pentagastrin, a dose-dependent
decrease in gastric acid output occurs after a single dose of oral (20-80 mg)
or a single dose of intravenous (20-120 mg) pantoprazole in healthy volunteers.
Pantoprazole given once daily results in increasing inhibition of gastric acid
secretion. Following the initial oral dose of 40 mg pantoprazole, a 51% mean
inhibition was achieved by 2.5 hours. With once a day dosing for 7 days the
mean inhibition was increased to 85%. Pantoprazole suppressed acid secretion
in excess of 95% in half of the subjects. Acid secretion had returned to normal
within a week after the last dose of pantoprazole; there was no evidence of
rebound hypersecretion.
In a series of dose-response studies pantoprazole, at oral doses ranging from
20 to 120 mg, caused dose-related increases in median basal gastric pH and in
the percent of time gastric pH was > 3 and > 4. Treatment with 40 mg of
pantoprazole produced optimal increases in gastric pH which were significantly
greater than the 20-mg dose. Doses higher than 40 mg (60, 80, 120 mg) did not
result in further significant increases in median gastric pH. The effects of
pantoprazole on median pH from one double-blind crossover study are shown below.
Effect of Single Daily Doses of Oral Pantoprazole on Intragastric
pH
| |
Median pH on day 7 |
| Time |
Placebo |
20 mg |
40 mg |
80 mg |
| 8 a.m. - 8 a.m. (24 hours) |
1.3 |
2.9* |
3.8*# |
3.9*# |
| 8 a.m. - 10 p.m. (Daytime) |
1.6 |
3.2* |
4.4*# |
4.8*# |
| 10 p.m. - 8 a.m. (Nighttime) |
1.2 |
2.1* |
3.0* |
2.6* |
*Significantly different from placebo
#Significantly different from 20 mg |
Serum Gastrin Effects
Fasting serum gastrin levels were assessed in two double-blind studies of the
acute healing of erosive esophagitis (EE) in which 682 patients with gastroesophageal
reflux disease (GERD) received 10, 20, or 40 mg of PROTONIX for up to 8 weeks.
At 4 weeks of treatment there was an increase in mean gastrin levels of 7%,
35%, and 72% over pretreatment values in the 10, 20, and 40 mg treatment groups,
respectively. A similar increase in serum gastrin levels was noted at the 8
week visit with mean increases of 3%, 26%, and 84% for the three pantoprazole
dose groups. Median serum gastrin levels remained within normal limits during
maintenance therapy with PROTONIX Delayed-Release Tablets.
In long-term international studies involving over 800 patients, a 2- to 3-fold
mean increase from the pretreatment fasting serum gastrin level was observed
in the initial months of treatment with pantoprazole at doses of 40 mg per day
during GERD maintenance studies and 40 mg or higher per day in patients with
refractory GERD. Fasting serum gastrin levels generally remained at approximately
2 to 3 times baseline for up to 4 years of periodic follow-up in clinical trials.
Following healing of gastric or duodenal ulcers with pantoprazole treatment,
elevated gastrin levels return to normal by at least 3 months.
Enterochromaffin-Like (ECL) Cell Effects
In 39 patients treated with oral pantoprazole 40 mg to 240 mg daily (majority
receiving 40 mg to 80 mg) for up to 5 years, there was a moderate increase in
ECL-cell density starting after the first year of use which appeared to plateau
after 4 years.
In a nonclinical study in Sprague-Dawley rats, lifetime exposure (24 months)
to pantoprazole at doses of 0.5 to 200 mg/kg/day resulted in dose-related increases
in gastric ECL-cell proliferation and gastric neuroendocrine (NE)-cell tumors.
Gastric NE-cell tumors in rats may result from chronic elevation of serum gastrin
concentrations. The high density of ECL cells in the rat stomach makes this
species highly susceptible to the proliferative effects of elevated gastrin
concentrations produced by proton pump inhibitors. However, there were no observed
elevations in serum gastrin following the administration of pantoprazole at
a dose of 0.5 mg/kg/day. In a separate study, a gastric NE-cell tumor without
concomitant ECL-cell proliferative changes was observed in 1 female rat following
12 months of dosing with pantoprazole at 5 mg/kg/day and a 9 month off-dose
recovery (see PRECAUTIONS, Carcinogenesis, Mutagenesis,
Impairment of Fertility).
Other Effects
No clinically relevant effects of pantoprazole on cardiovascular, respiratory,
ophthalmic, or central nervous system function have been detected. In a clinical
pharmacology study, pantoprazole 40 mg given once daily for 2 weeks had no effect
on the levels of the following hormones: cortisol, testosterone, triiodothyronine
(T3), thyroxine (T4), thyroid-stimulating hormone (TSH), thyronine-binding protein,
parathyroid hormone, insulin, glucagon, renin, aldosterone, follicle-stimulating
hormone, luteinizing hormone, prolactin, and growth hormone.
In a 1-year study of GERD patients treated with pantoprazole 40 mg or 20 mg,
there were no changes from baseline in overall levels of T3, T4, and TSH.
Clinical Studies
PROTONIX Delayed-Release Tablets were used in the following clinical trials:
Erosive Esophagitis (EE) Associated with Gastroesophageal Reflux Disease (GERD)
A U.S. multicenter double-blind, placebo-controlled study of PROTONIX 10 mg,
20 mg, or 40 mg once daily was conducted in 603 patients with reflux symptoms
and endoscopically diagnosed EE of grade 2 or above (Hetzel-Dent scale). In
this study, approximately 25% of enrolled patients had severe EE of grade 3
and 10% had grade 4. The percentages of patients healed (per protocol, n = 541)
in this study were as follows:
Erosive Esophagitis Healing Rates (per protocol)
| |
PROTONIX |
Placebo |
| Week |
10 mg QD
(n = 153) |
20 mg QD
(n = 158) |
40 mg QD
(n = 162) |
(n = 68) |
| 4 |
45.6%+ |
58.4%+# |
75.0%+* |
14.3% |
| 8 |
66.0%+ |
83.5 %+# |
92.6%+* |
39.7% |
+(p < 0.001) PROTONIX versus
placebo.
*(p < 0.05) versus 10 mg, or 20 mg PROTONIX
#(p < 0.05) versus 10 mg PROTONIX |
In this study, all PROTONIX treatment groups had significantly greater healing
rates than the placebo group. This was true regardless of H. pylori status
for the 40-mg and 20-mg PROTONIX treatment groups. The 40-mg dose of PROTONIX
resulted in healing rates significantly greater than those found with either
the 20- or 10-mg dose.
A significantly greater proportion of patients taking PROTONIX 40 mg experienced
complete relief of daytime and nighttime heartburn and the absence of regurgitation
starting from the first day of treatment compared with placebo. Patients taking
PROTONIX consumed significantly fewer antacid tablets per day than those taking
placebo.
PROTONIX 40 mg and 20 mg once daily were also compared with nizatidine 150
mg twice daily in a U.S. multicenter, double-blind study of 243 patients with
reflux symptoms and endoscopically diagnosed EE of grade 2 or above. The percentages
of patients healed (per protocol, n = 212) were as follows:
Erosive Esophagitis Healing Rates (per protocol)
| |
PROTONIX |
Nizatidine |
| Week |
20 mg QD
(n = 72) |
40 mg QD
(n = 70) |
150 mg BID
(n = 70) |
| 4 |
61.4%+ |
64.0%+ |
22.2% |
| 8 |
79.2%+ |
82.9%+ |
41.4% |
| +(p < 0.001) PROTONIX versus
nizatidine. |
Once daily treatment with PROTONIX 40 mg or 20 mg resulted in significantly
superior rates of healing at both 4 and 8 weeks compared with twice daily treatment
with 150 mg of nizatidine. For the 40 mg treatment group, significantly greater
healing rates compared to nizatidine were achieved regardless of the H. pylori
status.
A significantly greater proportion of the patients in the PROTONIX treatment
groups experienced complete relief of nighttime heartburn and regurgitation
starting on the first day and of daytime heartburn on the second day compared
with those taking nizatidine 150 mg twice daily. Patients taking PROTONIX consumed
significantly fewer antacid tablets per day than those taking nizatidine.
Long-Term Maintenance of Healing of Erosive Esophagitis
Two independent, multicenter, randomized, double-blind, comparator-controlled
trials of identical design were conducted in GERD patients with endoscopically-confirmed
healed erosive esophagitis to demonstrate efficacy of PROTONIX in long-term
maintenance of healing. The two U.S. studies enrolled 386 and 404 patients,
respectively, to receive either 10 mg, 20 mg, or 40 mg of PROTONIX Delayed-Release
Tablets once daily or 150 mg of ranitidine twice daily. As demonstrated in the
table below, PROTONIX 40 mg and 20 mg were significantly superior to ranitidine
at every time point with respect to the maintenance of healing. In addition,
PROTONIX 40 mg was superior to all other treatments studied.
Long-Term Maintenance of Healing of Erosive Gastroesophageal
Reflux Disease (GERD Maintenance): Percentage of Patients Who Remained Healed
| |
PROTONIX
20 mg QD |
PROTONIX
40 mg QD |
Ranitidine
150 mg BID |
| Study 1 |
n = 75 |
n = 74 |
n = 75 |
| Month 1 |
91* |
99* |
68 |
| Month 3 |
82* |
93*# |
54 |
| Month 6 |
76* |
90*# |
44 |
| Month 12 |
70* |
86*# |
35 |
| Study 2 |
n = 74 |
n = 88 |
n = 84 |
| Month 1 |
89* |
92*# |
62 |
| Month 3 |
78* |
91*# |
47 |
| Month 6 |
72* |
88*# |
39 |
| Month 12 |
72* |
83* |
37 |
*(p < 0.05 vs ranitidine)
#(p < 0.05 vs PROTONIX 20 mg) |
Note: PROTONIX 10 mg was superior (p < 0.05) to ranitidine in study 2 but
not study 1.
PROTONIX 40 mg was superior to ranitidine in reducing the number of daytime
and nighttime heartburn episodes from the first through the twelfth month of
treatment. PROTONIX 20 mg, administered once daily, was also effective in reducing
episodes of daytime and nighttime heartburn in one trial.
Number of Episodes of Heartburn (mean SD)
| |
|
PROTONIX
40 mg QD |
Ranitidine
150 mg BID |
| Month 1 |
Daytime |
5.1 ± 1.6* |
18.3 ± 1.6 |
| |
Nighttime |
3.9 ± 1.1* |
11.9 ± 1.1 |
| Month 12 |
Daytime |
2.9 ± 1.5* |
17.5 ± 1.5 |
| |
Nighttime |
2.5 ± 1.2* |
13.8 ± 1.3 |
| *(p < 0.001 vs ranitidine, combined data
from the 2 U.S. studies) |
Pathological Hypersecretory Conditions Including Zollinger-Ellison Syndrome
In a multicenter, open-label trial of 35 patients with pathological hypersecretory
conditions, such as Zollinger-Ellison syndrome with or without multiple endocrine
neoplasia-type I, PROTONIX successfully controlled gastric acid secretion. Doses
ranging from 80 mg daily to 240 mg daily maintained gastric acid output below
10 mEq/h in patients without prior acid-reducing surgery and below 5 mEq/h in
patients with prior acid-reducing surgery.
Doses were initially titrated to the individual patient needs, and adjusted
in some patients based on the clinical response with time (see DOSAGE
AND ADMINISTRATION). PROTONIX was well tolerated at these dose levels
for prolonged periods (greater than 2 years in some patients).
Last updated on RxList: 12/17/2007