Cimetidine has been used for the treatment and/or prophylaxis of gastric, abomasal and duodenal ulcers, uremic gastritis, stress-related or drug-induced erosive gastritis, esophagitis, duodenal gastric reflux and esophageal reflux. It has also been employed to treat hypersecretory conditions associated with gastrinomas and systemic mastocytosis. Cimetidine is also used as a immunomodulating agent in dogs.
Storage/Stability/Compatibility
Cimetidine products should be stored protected from light and kept at room temperature. Do not refrigerate the injectable product as precipitation may occur. Oral dosage forms should be stored in tight containers.
The cimetidine injectable product is compatible with the commonly used IV infusions solutions, including amino acid (TPN) solutions, but should be used within 48 hours of dilution. Cimetidine is also reported to be compatible with the following drugs: acetazolamide sodium, amikacin sulfate, atropine sulfate, carbenicillin disodium, cefoxitin sodium, chlorothiazide sodium, clindamycin phosphate, colistimethate sodium, dexamethasone sodium phosphate, digoxin, epinephrine, erythromycin lactobionate, furosemide, gentamicin sulfate, heparin sodium, insulin (regular), isoproterenol HCl, lidocaine HCl, lincomycin HCl, methylprednisolone sodium succinate, nafcillin sodium, norepinephrine bitartrate, penicillin G potassium/sodium, phytonadione, polymyxin B sulfate, potassium chloride, protamine sulfate, quinidine gluconate, sodium nitroprusside, tetracycline HCl, vancomycin HCl, verapamil HCl, and vitamin B complex (w/ or w/o C).
The following drugs are reported to be either incompatible with cimetidine or data are conflicting: amphotericin B, ampicillin sodium, cefamandole naftate, cefazolin sodium, cephalothin sodium, and pentobarbital sodium. Compatibility is dependent upon factors such as pH, concentration, temperature and diluents used.
Pharmacology
At the H2 receptors of the parietal cells, cimetidine competitively inhibits histamine, thereby reducing gastric acid output both during basal conditions and when stimulated by food, pentagastrin, histamine or insulin. Gastric emptying time, pancreatic or biliary secretion, and lower esophageal pressures are not altered by cimetidine. By decreasing the amount of gastric juice produced, cimetidine also decreases the amount of pepsin secreted.
Cimetidine has an apparent immunomodulating effect as it has been demonstrated to reverse suppressor T cell-mediated immune suppression. It also possesses weak anti-androgenic activity.
Contraindications/Precautions
Cimetidine is contraindicated in patients with known hypersensitivity to the drug.
Cimetidine should be used cautiously in geriatric patients and in patients with significantly impaired hepatic or renal function. In humans meeting these criteria, increased risk of CNS (confusion) effects may occur; dosage reductions may be necessary.
Adverse Effects/Warnings
Adverse effects appear to be very rare in animals at the dosages generally used. Potential adverse effects (documented in humans) that could be seen, include mental confusion, headache (upon discontinuation of the drug), gynecomastia and decreased libido. Rarely, agranulocytosis may develop and if given rapidly IV, transient cardiac arrhythmias may be seen. Pain at the injection site may be noted after IM administration.
Overdosage
Clinical experience with cimetidine overdosage is limited. In laboratory animals, very high dosages have been associated with tachycardia and respiratory failure. Respiratory support and beta-adrenergic blockers have been suggested for use should these symptoms occur.
Drug Interactions
Cimetidine may inhibit the hepatic microsomal enzyme system and thereby reduce the metabolism, prolong serum half-lives, and increase the serum levels of several drugs. It may also reduce the hepatic blood flow and reduce the amount of hepatic extraction of drugs that have a high first-pass effect. The following drugs may be affected: beta-blockers (e.g.,propranolol), lidocaine, chloramphenicol, quinidine, calcium channel blockers (e.g.,verapamil), diazepam (and other benzodiazepines), ethanol, metronidazole, phenytoin, quinidine, theophylline, and warfarin. Dosage adjustment or increased therapeutic monitoring may be necessary.
Cimetidine may exacerbate leukopenias when used with other agents that can cause this problem.
Stagger doses (separate by 2 hours if possible) of cimetidine with antacids, metoclopramide, sucralfate, digoxin, and ketoconazole.
Drug/Laboratory Interactions
Cimetidine may cause small increases in plasma creatinine concentrations early in therapy. These increases are generally mild, non-progressive, and have disappeared when therapy is discontinued.Histamine2 blockers may antagonize the effects of histamine and pentagastrin in the evaluation gastric acid secretion. After using allergen extract skin tests, histamine2 antagonists may inhibit histamine responses. It is recommended that histamine2 blockers be discontinued at least 24 hours before performing either of these tests.
How Supplied:
Cimetidine Tablets 200 mg, 300 mg, 400 mg, 800 mg. Cimetidine is a Tagamet Generic.
Rx Only
Additional information not available for this medicine.