Omeprazole and Sodium Bicrabonate (Page 5 of 10)
8.4 Pediatric Use
Safety and effectiveness of omeprazole and sodium bicarbonate have not been established in pediatric patients.
Juvenile Animal Data
Esomeprazole, an enantiomer of omeprazole, was shown to decrease body weight, body weight gain, femur weight, femur length, and overall growth at oral doses about 34 to 68 times a daily human dose of 40 mg esomeprazole or 40 mg omeprazole based on body surface area in a juvenile rat toxicity study. The animal to human dose multiples are based on the assumption of equal systemic exposure to esomeprazole in humans following oral administration of either 40 mg esomeprazole or 40 mg omeprazole.
A 28-day toxicity study with a 14-day recovery phase was conducted in juvenile rats with esomeprazole magnesium at doses of 70 to 280 mg/kg/day (about 17 to 68 times a daily oral human dose of 40 mg esomeprazole or 40 mg omeprazole on a body surface area basis). An increase in the number of deaths at the high dose of 280 mg/kg/day was observed when juvenile rats were administered esomeprazole magnesium from postnatal day 7 through postnatal day 35. In addition, doses equal to or greater than 140 mg/kg/day (about 34 times a daily oral human dose of 40 mg esomeprazole or 40 mg omeprazole on a body surface area basis), produced treatment-related decreases in body weight (approximately 14%) and body weight gain, decreases in femur weight and femur length, and affected overall growth. Comparable findings described above have also been observed in this study with another esomeprazole salt, esomeprazole strontium, at equimolar doses of esomeprazole.
8.5 Geriatric Use
Omeprazole was administered to over 2,000 elderly individuals (≥65 years of age) in clinical trials in the U.S. and Europe. There were no differences in safety and effectiveness between the elderly and younger subjects. Other reported clinical experience has not identified differences in response between the elderly and younger subjects, but greater sensitivity of some older individuals cannot be ruled out.
Pharmacokinetic studies with buffered omeprazole have shown the elimination rate was somewhat decreased in the elderly and bioavailability was increased. The plasma clearance of omeprazole was 250 mL/min (about half that of young subjects). The plasma half-life averaged one hour, about twice that in nonelderly, healthy subjects taking omeprazole and sodium bicarbonate. However, no dosage adjustment is necessary in the elderly. [see Clinical Pharmacology (12.3)]
8.6 Hepatic Impairment
In patients with hepatic impairment (Child-Pugh Class A, B, or C) exposure to omeprazole substantially increased compared to healthy subjects. Avoid use of omeprazole and sodium bicarbonate in patients with hepatic impairment for maintenance of healing of erosive esophagitis [see Clinical Pharmacology (12.3)]
8.7 Asian Population
In studies of healthy subjects, Asians had approximately a four-fold higher exposure than Caucasians. Avoid use of omeprazole and sodium bicarbonate in Asian patients for maintenance of healing of erosive esophagitis. [see Clinical Pharmacology (12.5)]
If over-exposure occurs, call your Poison Control Center at 1-800-222-1222 for current information on the management of poisoning or overdosage.
Reports have been received of overdosage with omeprazole in humans. Doses ranged up to 2,400 mg (120 times the usual recommended clinical dose). Manifestations were variable, but included confusion, drowsiness, blurred vision, tachycardia, nausea, vomiting, diaphoresis, flushing, headache, dry mouth, and other adverse reactions similar to those seen in clinical experience with the recommended dosage [see Adverse Reactions (6)]. Symptoms were transient, and no serious clinical outcome has been reported when omeprazole was taken alone. No specific antidote for omeprazole overdosage is known. Omeprazole is extensively protein bound and is, therefore, not readily dialyzable. In the event of overdosage, treatment should be symptomatic and supportive.
Overdosage of sodium bicarbonate can cause electrolyte abnormalities (hypocalcemia, hypokalemia, hypernatremia), metabolic alkalosis, and seizures. Institute supportive care and correct electrolyte abnormalities.
Omeprazole and sodium bicarbonate capsules, USP are a combination of omeprazole USP, a proton-pump inhibitor, and sodium bicarbonate USP, an antacid. Omeprazole USP, is a substituted benzimidazole, 5-methoxy-2-[[(4-methoxy-3,5-dimethyl-2 pyridinyl)methyl]sulfinyl]-1H-benzimidazole, a racemic mixture of two enantiomers that inhibits gastric acid secretion. Its empirical formula is C17 H19 N3 O3 S, with a molecular weight of 345.42.
The structural formula is:
Omeprazole, USP is a white to off-white powder, melts between 150°C and 160°C with decomposition. It is soluble in dichloromethane, sparingly soluble in methanol and in alcohol. The stability of omeprazole USP is a function of pH; it is rapidly degraded in acid media, but has acceptable stability under alkaline conditions.
Omeprazole and sodium bicarbonate capsules, USP are supplied as immediate-release capsules. Each capsule contains either 40 mg or 20 mg of omeprazole USP and 1100 mg of sodium bicarbonate USP with the following excipients: colloidal silicon dioxide, croscarmellose sodium and sodium stearyl fumerate. Each hard gelatin capsule contains: FD&C Blue No.1 (for 40 mg) FD&C Red No.40 (for 40 mg), gelatin, sodium lauryl sulfate and titanium dioxide. White Imprinting Ink contains: Potassium hydroxide, propylene glycol, shellac, strong ammonia solution and titanium dioxide. Blue Imprinting Ink (for 40 mg) contains: FD&C Blue no.2 aluminum lake, propylene glycol, shellac, strong ammonia solution.
Omeprazole and sodium bicarbonate capsules, USP are immediate-release formulations that contain sodium bicarbonate which raises the gastric pH and thus protects omeprazole from acid degradation.
12 CLINICAL PHARMACOLOGY
12.1 Mechanism of Action
Omeprazole belongs to a class of antisecretory compounds, the substituted benzimidazoles, that suppress gastric acid secretion by specific inhibition of the H+/K+ ATPase enzyme system at the secretory surface of the gastric parietal cell. Because this enzyme system is regarded as the acid (proton) pump within the gastric mucosa, omeprazole has been characterized as a gastric acid-pump inhibitor, in that it blocks the final step of acid production. This effect is dose related and leads to inhibition of both basal and stimulated acid secretion irrespective of the stimulus.
Results from a pharmacokinetic/pharmacodynamic (PK/PD) study of the antisecretory effect of repeated once-daily dosing of 40 mg and 20 mg of omeprazole and sodium bicarbonate for oral suspension in healthy subjects are shown in Table 8 below.
Table 8: Effect of Omeprazole and Sodium Bicarbonate for Oral Suspension on Intragastric pH, Day 7
|Once-Daily Dosage of Omeprazole and Sodium Bicarbonate for Oral Suspension|
|Parameter||40 mg omeprazole and 1,680 mg sodium bicarbonate (n = 24)||20 mg omeprazole and 1,680 mg sodium bicarbonate (n = 28)|
|% Decrease from Baseline for Integrated Gastric Acidity (mmol•hr/L)||84%||82%|
|Coefficient of Variation||20%||24%|
|% Time Gastric pH > 4 1 (Hours)1||77%(18.6 h)||51%(12.2 h)|
|Coefficient of Variation||27%||43%|
|Coefficient of Variation||17%||37%|
|Note: Values represent medians. All parameters were measured over a 24-hour period.|
1 P < 0.05 20 mg vs. 40 mg
Results from a separate PK/PD study of antisecretory effect on repeated once-daily dosing of 40 mg/1,100 mg and 20 mg/1,100 mg of omeprazole and sodium bicarbonate capsules in healthy subjects show similar effects in general on the above three PD parameters as those for omeprazole and sodium bicarbonate for oral suspension 40 mg/1,680 mg and 20 mg/1,680 mg, respectively.
The antisecretory effect lasts longer than would be expected from the very short (1 hour) plasma half-life, apparently due to irreversible binding to the parietal H+/K+ ATPase enzyme.
Enterochromaffin-like (ECL) Cell Effects
Human gastric biopsy specimens have been obtained from more than 3000 patients treated with omeprazole in long-term clinical trials. The incidence of ECL cell hyperplasia in these studies increased with time; however, no case of ECL cell carcinoids, dysplasia, or neoplasia has been found in these patients. These studies are of insufficient duration and size to rule out the possible influence of long-term administration of omeprazole on the development of any premalignant or malignant conditions.
Serum Gastrin Effects
In studies involving more than 200 patients, serum gastrin levels increased during the first 1 to 2 weeks of once-daily administration of therapeutic doses of omeprazole in parallel with inhibition of acid secretion. No further increase in serum gastrin occurred with continued treatment. In comparison with histamine H2-receptor antagonists, the median increases produced by 20 mg doses of omeprazole were higher (1.3 to 3.6-fold vs. 1.1- to 1.8-fold increase). Gastrin values returned to pretreatment levels, usually within 1 to 2 weeks after discontinuation of therapy.
Increased gastrin causes enterochromaffin-like cell hyperplasia and increased serum Chromogranin A (CgA) levels. The increased CgA levels may cause false positive results in diagnostic investigations for neuroendocrine tumors [seeWarnings and Precautions (5.11)].
Systemic effects of omeprazole in the central nervous system (CNS), cardiovascular and respiratory systems have not been found to date. Omeprazole, given in oral doses of 30 or 40 mg for 2 to 4 weeks, had no effect on thyroid function, carbohydrate metabolism, or circulating levels of parathyroid hormone, cortisol, estradiol, testosterone, prolactin, cholecystokinin or secretin.
No effect on gastric emptying of the solid and liquid components of a test meal was demonstrated after a single dose of omeprazole 90 mg. In healthy subjects, a single intravenous dose of omeprazole (0.35 mg/kg) had no effect on intrinsic factor secretion. No systematic dose-dependent effect has been observed on basal or stimulated pepsin output in humans. However, when intragastric pH is maintained at 4.0 or above, basal pepsin output is low, and pepsin activity is decreased.
As do other agents that elevate intragastric pH, omeprazole administered for 14 days in healthy subjects produced a significant increase in the intragastric concentrations of viable bacteria. The pattern of the bacterial species was unchanged from that commonly found in saliva. All changes resolved within three days of stopping treatment.
The course of Barrett’s esophagus in 106 patients was evaluated in a U.S. double-blind controlled study of omeprazole 40 mg twice daily for 12 months followed by 20 mg twice daily for 12 months or ranitidine 300 mg twice daily for 24 months. No clinically significant impact on Barrett’s mucosa by antisecretory therapy was observed. Although neosquamous epithelium developed during antisecretory therapy, complete elimination of Barrett’s mucosa was not achieved. No significant difference was observed between treatment groups in development of dysplasia in Barrett’s mucosa, and no patient developed esophageal carcinoma during treatment. No significant differences between treatment groups were observed in development of ECL cell hyperplasia, corpus atrophic gastritis, corpus intestinal metaplasia, or colon polyps exceeding 3 mm in diameter.
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