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 as a immunomodulating agent in
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.
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
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.
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 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.
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.
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
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
1. 5-10 mg/kg PO q6h (do not give with antacids)
2. 4 mg/kg PO qid
For prevention of drug-induced gastric
1. 5 mg/kg PO, SC, tid
For chronic gastritis:
1. 5-10 mg/kg PO, IM or IV tid-qid
For ulcer disease:
1. 5-10 mg/kg PO, IM or IV tid-qid
2. 4-5 mg/kg PO, IV, or SC tid-qid
3. 5 mg/kg IV or PO qid
4. 5-10 mg/kg PO q6-8h or 10 mg/kg q6h as a slow (over 30
minutes) IV infusion
5. 10 mg/kg PO, IM, IV q8h
1. 5-10 mg/kg PO, SC, IV q6-8h
To prevent histamine-mediated gastric
hyperacidity/ulceration secondary to mast cell tumors:
1. 5 mg/kg q8h
2. 5 mg/kg PO, IV, tid-qid
To decrease gastric acid hypersecretion during the
treatment of alkalosis:
1. 5-10 mg/kg tid-qid
As an immunomodulating agent (reverses suppressor T
cell-mediated immune suppression):
1. 10-25 mg/kg PO bid
1. 5-10 mg/kg PO q6-8h or 10 mg/kg q6h as a slow (over 30
minutes) IV infusion
1. For stress induced ulcers: 5-10 mg/kg PO, SC, IM or IV 3
1. Rabbits: For GI ulcers: 5-10 mg/kg PO, SC, IM or
2. Mice, Rats, Gerbils, Hamsters,
Guinea pigs, Chinchillas: 5-10 mg/kg PO, IM or SC q6-12h
To treat abomasal ulcers: 8-16 mg/kg tid (method
of administration not specified); relatively expensive and may be only of
1. 1000 mg divided bid or tid PO, IV or IM
2. 300-600 mg PO or IV 4 times a day
To treat gastric ulcers:
1. 300 mg per animal twice daily
In most species:
1. 4 mg/kg PO q8-12h
Cimetidine Tablets 200 mg, 300 mg, 400 mg, 800 mg. Cimetidine is a Tagamet Generic.
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