Overview
DESCRIPTION Cimetidine, USP is a histamine H 2 -receptor antagonist. Chemically it is N" -cyano- N -methyl- N' -[2-[[(5-methyl-1 H -imidazol-4-yl)methyl]thio]-ethyl]guanidine. Its structural formula is: Cimetidine, USP contains an imidazole ring, and is chemically related to histamine. Cimetidine, USP has a bitter taste and characteristic odor.
Mechanism of Action
CLINICAL PHARMACOLOGY Cimetidine tablets competitively inhibits the action of histamine at the histamine H 2 receptors of the parietal cells and thus is a histamine H 2 -receptor antagonist. Cimetidine is not an anticholinergic agent. Studies have shown that cimetidine tablets inhibit both daytime and nocturnal basal gastric acid secretion. Cimetidine tablets also inhibit gastric acid secretion stimulated by food, histamine, pentagastrin, caffeine and insulin. Antisecretory Activity 1) Acid Secretion Nocturnal An 800 mg oral dose of cimetidine tablets 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.
Indications
- INDICATIONS AND USAGE Cimetidine tablets are indicated in: 1. Short-term treatment of active duodenal ulcer. Most patients heal within 4 weeks and there is rarely reason to use cimetidine tablets at full dosage for longer than 6 to 8 weeks (see DOSAGE AND ADMINISTRATION: Duodenal Ulcer ). Concomitant antacids should be given as needed for relief of pain. However, simultaneous administration of cimetidine tablets and antacids is not recommended, since antacids have been reported to interfere with the absorption of cimetidine. 2.
Common Doses
- 400 mg
- 800 mg
- 1600 mg
- 600 mg
Dosage
DOSAGE AND ADMINISTRATION Duodenal Ulcer Active Duodenal Ulcer Clinical studies have indicated that suppression of nocturnal acid is the most important factor in duodenal ulcer healing (see CLINICAL PHARMACOLOGY: Antisecretory Activity: Acid Secretion ). This is supported by recent clinical trials (see CLINICAL TRIALS: Duodenal Ulcer: Active Duodenal Ulcer ). Therefore, there is no apparent rationale, except for familiarity with use, for treating with anything other than a once-daily at bedtime dosage regimen. In a U.S.
Contraindications
- CONTRAINDICATIONS Cimetidine tablets are contraindicated for patients known to have hypersensitivity to the product.
Side Effects
- ADVERSE REACTIONS Adverse effects reported in patients taking cimetidine tablets are described as follows by body system. Incidence figures of 1 in 100 and greater are generally derived from controlled clinical studies. Gastrointestinal Diarrhea (usually mild) has been reported in approximately 1 in 100 patients. CNS Headaches, ranging from mild to severe, have been reported in 3.5% of 924 patients taking 1,600 mg/day, 2.1% of 2,225 patients taking 800 mg/day and 2.3% of 1,897 patients taking placebo.
Interactions
- No major interactions listed on the FDA label. Always consult a healthcare professional.