What is cimetidine, and how does it work (mechanism of action)?
Cimetidine is a drug that blocks the production of acid by acid-producing cells in the stomach and can be administered orally, IM or IV. It belongs to a class of drugs called H2 (histamine-2) blockers that also includes ranitidine (Zantac), nizatidine (Axid), and famotidine (Pepcid). Histamine is a naturally-occurring chemical that stimulates cells in the stomach (parietal cells) to produce acid. H2-blockers inhibit the action of histamine on the cells, thus reducing the production of acid by the stomach. Since excessive stomach acid can damage the esophagus, stomach, and duodenum by reflux and lead to inflammation and ulceration, reducing stomach acid prevents and allows acid-induced inflammation and ulcers to heal. Cimetidine was approved by the FDA in 1977.
Do I need a prescription for cimetidine?
Yes and OTC (Heart Burn)
What are the side effects of cimetidine?
Side effects due to cimetidine are rare and generally reversible once the medication is stopped. Minor side effects include:
Major side effects include confusion and hallucinations (usually in elderly or critically ill patients), enlargement of the breasts; impotence (usually seen in patients on high doses for prolonged periods); decreased white blood cell counts.
Other side effects include:
- What is cimetidine, and how does it work (mechanism of action)?
- What brand names are available for cimetidine?
- Is cimetidine available as a generic drug?
- Do I need a prescription for cimetidine?
- What are the side effects of cimetidine?
- What is the dosage for cimetidine?
- Which drugs or supplements interact with cimetidine?
- Is cimetidine safe to take if I'm pregnant or breastfeeding?
- What else should I know about cimetidine?
What is the dosage for cimetidine?
Duodenal ulcers are treated with 800 to 1600 mg at bedtime or 300 mg 4 times a day at meal times and bedtime, or 400 mg twice a day for 4-6 weeks. Maintenance therapy is 400 mg at bedtime.
Active gastric ulcers are treated with 800 mg at bedtime or 300 mg 4 times a day at meal times and bedtime for up to 8 weeks.
The regimen for GERD is 800 mg twice a day or 400 mg 4 times a day for 12 weeks.
Pathological hypersecretory conditions are treated with 300 mg 4 times daily up to 2400 mg daily.
For hospitalized patients who cannot take oral medications, 300 mg of cimetidine may be administered by intravenous or intramuscular injection every 6-8 hours. A continuous intravenous infusion of 37.5 to 50 mg/hour also may be used.
Which drugs or supplements interact with cimetidine?
Cimetidine may increase the blood levels of several drugs by reducing their elimination by the liver. This interaction may occur between cimetidine and warfarin (Coumadin), a commonly used blood thinning agent. Patients taking both medications should have frequent blood monitoring to avoid accumulation of high levels of warfarin leading to excessive blood thinning and bleeding.
Cimetidine also may increase the blood levels phenytoin (Dilantin, Dilantin-125), theophylline (Respbid, Slo-Bid, Theo-24, Theolair), lidocaine, amiodarone (Cordarone), metronidazole (Flagyl), loratadine, calcium channel blockers (for example, diltiazem (Cardizem, Dilacor, Tiazac), felodipine (Plendil), nifedipine (Adalat, Procardia, Afeditab, Nifediac), bupropion (Wellbutrin, Wellbutrin SR, Wellbutrin XL, Zyban, Aplenzin, Forfivo XL), carbamazepine (Tegretol Tegretol XR, Equetro, Carbatrol), and fluvastatin (Lescol, Lescol XL).
Because cimetidine reduces stomach acid, it may reduce the absorption of drugs (for example, ketoconazole [Nizoral, Extina, Xolegel, Kuric]) that are best absorbed in acidic conditions. Such drugs should be administered at least 2 hours before the administration of cimetidine.
Is cimetidine safe to take if I'm pregnant or breastfeeding?
There are no adequate studies of cimetidine in pregnant women.
Cimetidine is excreted in breast milk.
Cimetidine (Tagamet) is a drug prescribed for the treatment of GERD, duodenal ulcers, active gastric ulcers, Zollinger Ellison syndrome, heartburn, indigestion; and the prevention of gastrointestinal bleeding. Side effects, drug interactions, dosage, storage, and pregnancy safety information should be reviewed prior to taking this medication.
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