Rabeprazole Sodium (Page 5 of 10)

Effects on Esophageal Acid Exposure

In patients with gastroesophageal reflux disease (GERD) and moderate to severe esophageal acid exposure, Rabeprazole Sodium Delayed-Release 20 mg and 40 mg tablets per day decreased 24-hour esophageal acid exposure. After seven days of treatment, the percentage of time that esophageal pH<4 decreased from baselines of 24.7% for 20 mg and 23.7% for 40 mg, to 5.1% and 2%, respectively. Normalization of 24-hour intraesophageal acid exposure was correlated to gastric pH>4 for at least 35% of the 24-hour period; this level was achieved in 90% of subjects receiving Rabeprazole Sodium Delayed-Release Tablets 20 mg and in 100% of subjects receiving Rabeprazole Sodium Delayed-Release Tablets 40 mg. With Rabeprazole Sodium Delayed-Release Tablets 20 mg and 40 mg per day, significant effects on gastric and esophageal pH were noted after one day of treatment, and more pronounced after seven days of treatment.

Effects on Serum Gastrin

In patients given daily doses of Rabeprazole Sodium Delayed-Release Tablets for up to eight weeks to treat ulcerative or erosive esophagitis and in patients treated for up to 52 weeks to prevent recurrence of disease the median fasting gastrin level increased in a dose-related manner. The group median values stayed within the normal range.

In a group of subjects treated daily with Rabeprazole Sodium Delayed-Release Tablets 20 mg for 4 weeks a doubling of mean serum gastrin concentrations was observed. Approximately 35% of these treated subjects developed serum gastrin concentrations above the upper limit of normal. In a study of CYP2C19 genotyped subjects in Japan, poor metabolizers developed statistically significantly higher serum gastrin concentrations than extensive metabolizers.

Effects on Enterochromaffin-like (ECL) Cells

Increased serum gastrin secondary to antisecretory agents stimulates proliferation of gastric ECL cells which, over time, may result in ECL cell hyperplasia in rats and mice and gastric carcinoids in rats, especially in females [see Nonclinical Toxicology (13.1) ].

In over 400 patients treated with Rabeprazole Sodium Delayed-Release Tablets (10 or 20 mg/day) for up to one year, the incidence of ECL cell hyperplasia increased with time and dose, which is consistent with the pharmacological action of the proton-pump inhibitor. No patient developed the adenomatoid, dysplastic, or neoplastic changes of ECL cells in the gastric mucosa. No patient developed the carcinoid tumors observed in rats.

Endocrine Effects

Studies in humans for up to one year have not revealed clinically significant effects on the endocrine system. In healthy male volunteers treated with Rabeprazole Sodium Delayed-Release Tablets for 13 days, no clinically relevant changes have been detected in the following endocrine parameters examined: 17 β-estradiol, thyroid stimulating hormone, tri-iodothyronine, thyroxine, thyroxine-binding protein, parathyroid hormone, insulin, glucagon, renin, aldosterone, follicle-stimulating hormone, luteotrophic hormone, prolactin, somatotrophic hormone, dehydroepiandrosterone, cortisol-binding globulin, and urinary 6β-hydroxycortisol, serum testosterone and circadian cortisol profile.

Other Effects

In humans treated with Rabeprazole Sodium Delayed-Release Tablets for up to one year, no systemic effects have been observed on the central nervous, lymphoid, hematopoietic, renal, hepatic, cardiovascular, or respiratory systems. No data are available on long-term treatment with Rabeprazole Sodium Delayed-Release Tablets and ocular effects.

Microbiology

The following in vitro data are available but the clinical significance is unknown.

Rabeprazole sodium, amoxicillin and clarithromycin as a three drug regimen has been shown to be active against most strains of Helicobacter pylori in vitro and in clinical infections as described in the Clinical Studies (14) and Indications and Usage (1) sections.

Helicobacter pylori

Susceptibility testing of H. pylori isolates was performed for amoxicillin and clarithromycin using agar dilution methodology1 , and minimum inhibitory concentrations (MICs) were determined.

Standardized susceptibility test procedures require the use of laboratory control microorganisms to control the technical aspects of the laboratory procedures.

Incidence of Antibiotic-Resistant Organisms Among Clinical Isolates

Pretreatment Resistance: Clarithromycin pretreatment resistance rate (MIC ≥ 1 µg/mL) to H. pylori was 9% (51/560) at baseline in all treatment groups combined. A total of > 99% (558/560) of patients had H. pylori isolates, which were considered to be susceptible (MIC ≤ 0.25 µg/mL) to amoxicillin at baseline. Two patients had baseline H. pylori isolates with an amoxicillin MIC of 0.5 µg/mL.

For susceptibility testing information about Helicobacter pylori , see Microbiology section in prescribing information for clarithromycin and amoxicillin.

TABLE 6 CLARITHROMYCIN SUSCEPTIBILITY TEST RESULTS AND CLINICAL/BACTERIOLOGIC OUTCOMES * FOR A THREE DRUG REGIMEN (RABEPRAZOLE 20 MG TWICE DAILY, AMOXICILLIN 1000 MG TWICE DAILY, AND CLARITHROMYCIN 500 MG TWICE DAILY FOR 7 OR 10 DAYS)
Days of RAC Therapy Clarithromycin Pretreatment Results Total Number H. pylori Negative (Eradicated) H. pylori Positive (Persistent)Post-Treatment Susceptibility Results
S I R No MIC
*
Includes only patients with pretreatment and post-treatment clarithromycin susceptibility test results.
Susceptible (S) MIC ≤ 0.25 µg/mL, Intermediate (I) MIC = 0.5 µg/mL, Resistant (R) MIC ≥ 1 µg/mL
7 Susceptible 129 103 2 0 1 23
7 Intermediate 0 0 0 0 0 0
7 Resistant 16 5 2 1 4 4
10 Susceptible 133 111 3 1 2 16
10 Intermediate 0 0 0 0 0 0
10 Resistant 9 1 0 0 5 3

Patients with persistent H. pylori infection following rabeprazole, amoxicillin, and clarithromycin therapy will likely have clarithromycin resistant clinical isolates. Therefore, clarithromycin susceptibility testing should be done when possible. If resistance to clarithromycin is demonstrated or susceptibility testing is not possible, alternative antimicrobial therapy should be instituted.

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