Cimetidine
Cimetidine (Tagamet)
Cimetidine
(sye- MET-ih-deen)
Pregnancy Category: B Apo-Cimetidine Gen-Cimetidine Novo-Cimetine Nu-Cimet Peptol PMS-Cimetidine Tagamet (Rx) Tagamet HB (OTC)

Classification: Histamine H ₂ receptor blocking agent

See Also: See also Histamine H ₂ Antagonists .

Action/Kinetics: Reduces postprandial daytime and nighttime gastric acid secretion by about 50%-80%. May increase gastromucosal defense and healing in acid-related disorders (e.g., stress-induced ulcers) by increasing production of gastric mucus, increasing mucosal secretion of bicarbonate and gastric mucosal blood flow as well as increasing endogenous mucosal synthesis of prostaglandins. It also inhibits cytochrome P-450 and P-448, which will affect metabolism of drugs. Also possesses antiandrogenic activity and will increase prolactin levels following an IV bolus injection. Well absorbed from GI tract. Peak plasma level, PO: 45-90 min. Time to peak effect, after PO: 1-2 hr. Peak plasma levels, after PO use: 0.7-3.2 mcg/mL (after a 300 mg dose; after IV: 3.5-7.5 mcg/mL. Protein binding: 13%-25%. Duration, nocturnal: 6-8 hr; basal: 4-5 hr. t 1/2: 2 hr, longer in presence of renal impairment. After PO use, most metabolized in liver; after parenteral use, about 75% of drug excreted unchanged in the urine.

Uses: Rx. Treatment and maintenance of active duodenal ulcers. Short-term (6 weeks) treatment of benign gastric ulcers (in rare cases, healing has occurred). As part of multidrug regimen to eradicate Helicobacter pylori. Management of gastric acid hypersecretory states (Zollinger-Ellison syndrome, systemic mastocytosis). GERD, including erosive esophagitis. Prophylaxis of UGI bleeding in critically ill hospitalized clients. Investigational: Prior to surgery to prevent aspiration pneumonitis, secondary hyperparathyroidism in chronic hemodialysis clients, prophylaxis of stress-induced ulcers, hyperparathyroidism, dyspepsia, herpes virus infections, tinea capitis, hirsute women, chronic idiopathic urticaria, dermatologic anaphylaxis, acetaminophen overdosage, warts, colorectal cancer.
OTC. Relief of symptoms of heartburn, acid indigestion, and sour stomach.

Contraindications: Children under 16, lactation. Cirrhosis, impaired liver and renal function.

Special Concerns: In geriatric clients with impaired renal or hepatic function, confusion is more likely to occur. Not recommended for children less than 16 years of age.

Side Effects: GI: Diarrhea, pancreatitis (rare), hepatitis, hepatic fibrosis. CNS: Dizziness, sleepiness, headache, confusion, delirium, hallucinations, double vision, dysarthria, ataxia. Severely ill clients may manifest agitation, anxiety, depression, disorientation, hallucinations, mental confusion, and psychosis. CV: Hypotension and arrhythmias following rapid IV administration. Hematologic: Agranulocytosis, thrombocytopenia, hemolytic or aplastic anemia granulocytopenia. GU: Impotence (high doses for prolonged periods of time), gynecomastia (long-term treatment). Dermatologic: Exfoliative dermatitis, erythroderma, erythema multiforme. Musculoskeletal: Arthralgia, reversible worsening of joint symptoms with preexisting arthritis (including gouty arthritis). Other: Hypersensitivity reactions, pain at injection site, myalgia, rash, cutaneous vasculitis, peripheral neuropathy, galactorrhea, alopecia, bronchoconstriction.

Drug Interactions: Antacids / Effect of cimetidine R/T GI tract absorption Anticholinergics / Effect of cimetidine R/T GI tract absorption Benzodiazepines / Benzodiazepine effects R/T liver breakdown Beta-adrenergic blocking drugs / Beta-adrenergic effects R/T liver breakdown Caffeine / Caffeine effect R/T liver breakdown Calcium channel blockers / Calcium channel blocker effects R/T liver breakdown Carbamazepine / Carbamazepine effect R/T liver breakdown Carmustine / Additive bone marrow depression Chloroquine / Chloroquine effects R/T liver breakdown Chlorpromazine / Chlorpromazine effect R/T GI tract absorption Digoxin / Serum digoxin levels Flecainide / Flecainide effect Fluconazole / Fluconazole effect R/T GI tract absorption Fluorouracil / Serum fluorouracil levels following chronic cimetidine use Indomethacin / Indomethacin effect R/T GI tract absorption Iron salts / Iron salt effects R/T GI tract absorption Ketoconazole / Ketoconazole effect R/T GI tract absorption Labetalol / Labetalol effect R/T liver breakdown Lidocaine / Lidocaine effect R/T liver breakdown Metoclopramide / Cimetidine effect R/T GI tract absorption Metoprolol / Metoprolol effect R/T liver breakdown Metronidazole / Metronidazole effect R/T liver breakdown Moricizine / Moricizine effect R/T liver breakdown Narcotics / Possible toxic effects (respiratory depression) of narcotics Pentoxifylline / Pentoxifylline effect R/T liver breakdown Phenytoin / Phenytoin effect R/T liver breakdown Procainamide / Procainamide effect R/T kidney excretion Propafenone / Propafenone effect R/T liver breakdown Propranolol / Propranolol effect R/T liver breakdown Quinidine / Quinidine effect R/T liver breakdown Quinine / Quinine effect R/T liver breakdown Sildenafil / Sildenafil effect R/T liver breakdown Succinylcholine / Neuromuscular blockade respiratory depression and extended apnea Sulfonylureas / Sulfonylurea effects R/T liver breakdown Tacrine / Tacrine effect R/T liver breakdown Tetracyclines / Tetracycline effects R/T GI tract absorption Theophyllines / Theophylline effects R/T liver breakdown Tocainide / Tocainide effect Triamterene / Triamterene effect R/T liver breakdown Tricyclic antidepressants / TCA effects R/T liver breakdown Valproic acid / Valproic acid effect R/T liver breakdown Warfarin / Anticoagulant effects R/T liver breakdown

How Supplied: Injection: 150 mg/mL, 300 mg/2 mL; 300 mg/50 mL; Solution: 300 mg/5 mL; Suspension: 200 mg/5 mL; Tablet: 100 mg, 200 mg, 300 mg, 400 mg, 800 mg

Dosage
?Tablets, Oral Solution Duodenal ulcers, short-term.
Adults: 800 mg at bedtime. Alternate dosage: 300 mg q.i.d. with meals and at bedtime for 4-6 weeks (administer with antacids, staggering the dose of antacids) or 400 mg b.i.d. (in the morning and evening). Maintenance: 400 mg at bedtime.
Active benign gastric ulcers.
Adults: 800 mg at bedtime (preferred regimen) or 300 mg q.i.d. with meals and at bedtime for no more than 8 weeks.
Pathologic hypersecretory conditions.
Adults: 300 mg q.i.d. with meals and at bedtime up to a maximum of 2,400 mg/day for as long as needed.
Erosive gastroesophageal reflux disease.
Adults: 800 mg b.i.d. or 400 mg q.i.d. for 12 weeks. Use beyond 12 weeks has not been determined.
Dyspepsia.
Adults: 400 mg b.i.d.
Prophylaxis of aspiration pneumonitis.
Adults: 400-600 mg 60-90 min before anesthesia.
Primary hyperparathyroidism, secondary hyperparathyroidism in chronic hemodialysis clients.
Up to 1 g/day.
?Suspension, Tablets Heartburn, acid indigestion, sour stomach (OTC only).
200 mg, as symptoms present, up to b.i.d. Take tablets with water.
?IM, IV, IV Infusion Hospitalized clients with pathologic hypersecretory conditions or intractable ulcers or those unable to take PO medication.
Adults: 300 mg IM or IV q 6-8 hr. If an increased dose is necessary, administer 300 mg more frequently than q 6-8 hr, not to exceed 2,400 mg/day.
Prophylaxis of upper GI bleeding.
Adults: 50 mg/hr by continuous IV infusion. If C _CR is less than 30 mL/min, use one-half the recommended dose. Treatment beyond 7 days has not been studied.
Prophylaxis of aspiration pneumonitis.
Adults: 300 mg IV 60-90 min before induction of anesthetic.