Rabeprazole Sodium (Page 4 of 10)

Animal Data

Embryo-fetal developmental studies have been performed in rats at intravenous doses of rabeprazole up to 50 mg/kg/day (plasma AUC of 11.8 μg•hr/mL, about 13 times the human exposure at the recommended oral dose for GERD) and rabbits at intravenous doses up to 30 mg/kg/day (plasma AUC of 7.3 μg•hr/mL, about 8 times the human exposure at the recommended oral dose for GERD) and have revealed no evidence of harm to the fetus due to rabeprazole.

Administration of rabeprazole to rats in late gestation and during lactation at an oral dose of 400 mg/kg/day (about 195-times the human oral dose based on mg/m2) resulted in decreases in body weight gain of the pups.

A pre-and postnatal developmental toxicity study in rats with additional endpoints to evaluate bone development was performed with a different PPI at about 3.4 to 57 times an oral human dose on a body surface area basis. Decreased femur length, width and thickness of cortical bone, decreased thickness of the tibial growth plate and minimal to mild bone marrow hypocellularity were noted at doses of this PPI equal to or greater than 3.4 times an oral human dose on a body surface area basis. Physeal dysplasia in the femur was also observed in offspring after in utero and lactational exposure to the PPI at doses equal to or greater than 33.6 times an oral human dose on a body surface area basis. Effects on maternal bone were observed in pregnant and lactating rats in a pre- and postnatal toxicity study when the PPI was administered at oral doses of 3.4 to 57 times an oral human dose on a body surface area basis. When rats were dosed from gestational day 7 through weaning on postnatal day 21, a statistically significant decrease in maternal femur weight of up to 14% (as compared to placebo treatment) was observed at doses equal to or greater than 33.6 times an oral human dose on a body surface area basis.

8.3 Nursing Mothers

It is not known if Rabeprazole Sodium Delayed-Release Tablets is excreted in human milk; however, rabeprazole is present in rat milk. Because many drugs are excreted in milk, caution should be exercised when Rabeprazole Sodium Delayed-Release Tablets is administered to a nursing woman.

8.4 Pediatric Use

Symptomatic GERD in Adolescent Patients Greater or Equal to 12 Years of Age

In a multicenter, randomized, open-label, parallel-group study, 111 adolescent patients 12 to 16 years of age with a clinical diagnosis of symptomatic GERD, or suspected or endoscopically proven GERD were randomized and treated with either Rabeprazole Sodium 10 mg or Rabeprazole Sodium Delayed-Release Tablets 20 mg once daily for up to 8 weeks for the evaluation of safety and efficacy. The adverse event profile in adolescent patients was similar to that of adults. The related reported adverse reactions that occurred in ≥2% of patients were headache (5.4%) and nausea (1.8%). There were no adverse reactions reported in these studies that were not previously observed in adults.

8.5 Geriatric Use

Of the total number of subjects in clinical studies of Rabeprazole Sodium Delayed-Release Tablets, 19% were 65 years and over, while 4% were 75 years and over. No overall differences in safety or effectiveness were observed between these subjects and younger subjects, and other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out.

8.6 Gender

Duodenal ulcer and erosive esophagitis healing rates in women are similar to those in men. Adverse reactions and laboratory test abnormalities in women occurred at rates similar to those in men.

10 OVERDOSAGE

Because strategies for the management of overdose are continually evolving, it is advisable to contact a Poison Control Center to determine the latest recommendations for the management of an overdose of any drug. There has been no experience with large overdoses with rabeprazole. Seven reports of accidental overdosage with rabeprazole have been received. The maximum reported overdose was 80 mg. There were no clinical signs or symptoms associated with any reported overdose. Patients with Zollinger-Ellison syndrome have been treated with up to 120 mg rabeprazole QD. No specific antidote for rabeprazole is known. Rabeprazole is extensively protein bound and is not readily dialyzable. In the event of overdosage, treatment should be symptomatic and supportive.

Single oral doses of rabeprazole at 786 mg/kg and 1024 mg/kg were lethal to mice and rats, respectively. The single oral dose of 2000 mg/kg was not lethal to dogs. The major symptoms of acute toxicity were hypoactivity, labored respiration, lateral or prone position and convulsion in mice and rats and watery diarrhea, tremor, convulsion and coma in dogs.

11 DESCRIPTION

The active ingredient in Rabeprazole Sodium Delayed-Release Tablets is rabeprazole sodium, which is a proton pump inhibitor. It is a substituted benzimidazole known chemically as 2-[[[4-(3-methoxypropoxy)-3-methyl-2-pyridinyl]-methyl]sulfinyl]-1H- benzimidazole sodium salt. It has an empirical formula of C18 H20 N3 NaO3 S and a molecular weight of 381.42. Rabeprazole sodium is a white to slightly yellowish-white solid. It is very soluble in water and methanol, freely soluble in ethanol, chloroform and ethyl acetate and insoluble in ether and n-hexane. The stability of rabeprazole sodium is a function of pH; it is rapidly degraded in acid media, and is more stable under alkaline conditions. The structural formula is:

FIGURE 1
Figure 1
(click image for full-size original)

Rabeprazole Sodium Delayed-Release Tablets is available for oral administration as Delayed-Release, enteric-coated tablets containing 20 mg of rabeprazole sodium.

Inactive ingredients of the 20 mg tablet are crospovidone, FD&C Blue #1, glyceryl dibehenate, hypromellose, lactose monohydrate, methacrylic acid copolymer dispersion, talc and triethyl citrate.

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Rabeprazole belongs to a class of antisecretory compounds (substituted benzimidazole proton-pump inhibitors) that do not exhibit anticholinergic or histamine H2 -receptor antagonist properties, but suppress gastric acid secretion by inhibiting the gastric H+ , K+ ATPase at the secretory surface of the gastric parietal cell. Because this enzyme is regarded as the acid (proton) pump within the parietal cell, rabeprazole has been characterized as a gastric proton-pump inhibitor. Rabeprazole blocks the final step of gastric acid secretion.

In gastric parietal cells, rabeprazole is protonated, accumulates, and is transformed to an active sulfenamide. When studied in vitro , rabeprazole is chemically activated at pH 1.2 with a half-life of 78 seconds. It inhibits acid transport in porcine gastric vesicles with a half-life of 90 seconds.

12.2 Pharmacodynamics

Antisecretory Activity

The antisecretory effect begins within one hour after oral administration of 20 mg Rabeprazole Sodium Delayed-Release Tablets. The median inhibitory effect of Rabeprazole Sodium Delayed-Release Tablets on 24-hour gastric acidity is 88% of maximal after the first dose. Rabeprazole Sodium Delayed-Release Tablets 20 mg inhibits basal and peptone meal-stimulated acid secretion versus placebo by 86% and 95%, respectively, and increases the percent of a 24-hour period that the gastric pH>3 from 10% to 65% (see table below). This relatively prolonged pharmacodynamic action compared to the short pharmacokinetic half-life (1-2 hours) reflects the sustained inactivation of the H+ , K+ ATPase.

TABLE 3 GASTRIC ACID PARAMETERS RABEPRAZOLE SODIUM DELAYED-RELEASE TABLETS VERSUS PLACEBO AFTER 7 DAYS OF ONCE DAILY DOSING
Parameter Rabeprazole Sodium Delayed-Release Tablets(20 mg QD) Placebo
*

(p<0.01 versus placebo)

Basal Acid Output (mmol/hr) 0.4* 2.8
Stimulated Acid Output (mmol/hr) 0.6* 13.3
% Time Gastric pH>3 65* 10

Compared to placebo, Rabeprazole Sodium Delayed-Release Tablets, 10 mg, 20 mg, and 40 mg, administered once daily for 7 days significantly decreased intragastric acidity with all doses for each of four meal-related intervals and the 24-hour time period overall. In this study, there were no statistically significant differences between doses; however, there was a significant dose-related decrease in intragastric acidity. The ability of rabeprazole to cause a dose-related decrease in mean intragastric acidity is illustrated below.

TABLE 4 AUC ACIDITY (MMOL∙HR/L) RABEPRAZOLE SODIUM DELAYED-RELEASE TABLETS VERSUS PLACEBO ON DAY 7 OF ONCE DAILY DOSING (MEAN±SD)
Treatment
AUC interval (hrs) 10 mg RBP(N=24) 20 mg RBP(N=24) 40 mg RBP(N=24) Placebo(N=24)
*
(p<0.001 versus placebo)
08:00 – 13:00 19.6±21.5* 12.9±23* 7.6±14.7* 91.1±39.7
13:00 – 19:00 5.6±9.7* 8.3±29.8* 1.3±5.2* 95.5±48.7
19:00 – 22:00 0.1±0.1* 0.1±0.06* 0.0±0.02* 11.9±12.5
22:00 – 08:00 129.2±84* 109.6±67.2* 76.9±58.4* 479.9±165
AUC 0-24 hours 155.5±90.6* 130.9±81* 85.8±64.3* 678.5±216

After administration of 20 mg Rabeprazole Sodium Delayed-Release Tablets once daily for eight days, the mean percent of time that gastric pH>3 or gastric pH>4 after a single dose (Day 1) and multiple doses (Day 8) was significantly greater than placebo (see table below). The decrease in gastric acidity and the increase in gastric pH observed with 20 mg Rabeprazole Sodium Delayed-Release Tablets administered once daily for eight days were compared to the same parameters for placebo, as illustrated below:

TABLE 5 GASTRIC ACID PARAMETERS RABEPRAZOLE SODIUM DELAYED-RELEASE TABLETS ONCE DAILY DOSING VERSUS PLACEBO ON DAY 1 AND DAY 8
Parameter Rabeprazole Sodium Delayed-Release Tablets 20 mg QD Placebo
Day 1 Day8 Day 1 Day 8
*
(p<0.001 versus placebo)
No inferential statistics conducted for this parameter.
Gastric pH was measured every hour over a 24-hour period.
Mean AUC0-24 Acidity 340.8* 176.9* 925.5 862.4
Median trough pH (23-hr) 3.77 3.51 1.27 1.38
% Time Gastric pH>3 54.6* 68.7* 19.1 21.7
% Time Gastric pH>4 44.1* 60.3* 7.6 11

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