CIMETIDINE- cimetidine tablet, film coated
Mylan Pharmaceuticals Inc.
Cimetidine is a histamine H2 -receptor antagonist. Chemically it is N" -cyano-N -methyl-N� -[2-[[(5-methyl-1H -imidazol-4-yl)methyl]thio]-ethyl]guanidine. Its structural formula is:
Structural Formula
Cimetidine contains an imidazole ring, and is chemically related to histamine.
Cimetidine has a bitter taste and characteristic odor.
Solubility Characteristics
Cimetidine is soluble in alcohol, slightly soluble in water, very slightly soluble in chloroform and insoluble in ether.
Each tablet, for oral administration, contains 200 mg, 300 mg, 400 mg or 800 mg cimetidine, USP. Inactive ingredients are: croscarmellose sodium, crospovidone, hypromellose, lecithin, magnesium stearate, microcrystalline cellulose, polydextrose, polyethylene glycol, povidone, pregelatinized starch, sodium alginate, sodium lauryl sulfate, titanium dioxide, triacetin, vanillin, FD&C Blue No. 1 Aluminum Lake, FD&C Yellow No. 6 Aluminum Lake and D&C Yellow No. 10 Aluminum Lake.
CLINICAL PHARMACOLOGY
Cimetidine competitively inhibits the action of histamine at the histamine H2 receptors of the parietal cells and thus is a histamine H2 -receptor antagonist.
Cimetidine is not an anticholinergic agent. Studies have shown that cimetidine inhibits both daytime and nocturnal basal gastric acid secretion. Cimetidine also inhibits gastric acid secretion stimulated by food, histamine, pentagastrin, caffeine and insulin.
Antisecretory Activity
1) Acid Secretion
Nocturnal
An 800 mg oral dose of cimetidine at bedtime reduces mean hourly H+ activity by greater than 85% over an 8-hour period in duodenal ulcer patients, with no effect on daytime acid secretion. A 1600 mg oral dose of cimetidine at bedtime produces 100% inhibition of mean hourly H+ activity over an 8-hour period in duodenal ulcer patients, but also reduces H+ activity by 35% for an additional 5 hours into the following morning. Cimetidine given as 400 mg twice daily and 300 mg 4 times daily decreases nocturnal acid secretion in a dose related manner, i.e., 47% to 83% over a 6 to 8-hour period and 54% over a 9-hour period, respectively.
Food Stimulated
During the first hour after a standard experimental meal, a 300 mg oral dose of cimetidine inhibited gastric acid secretion in duodenal ulcer patients by at least 50%. During the subsequent 2 hours cimetidine inhibited gastric acid secretion by at least 75%.
The effect of a 300 mg breakfast dose of cimetidine continued for at least 4 hours and there was partial suppression of the rise in gastric acid secretion following the luncheon meal in duodenal ulcer patients. This suppression of gastric acid output was enhanced and could be maintained by another 300 mg dose of cimetidine given with lunch.
