Rare instances of cardiac arrhythmias and hypotension have been reported following the rapid
administration of Tagamet (cimetidine hydrochloride) Injection by intravenous bolus.
Symptomatic response to Tagamet therapy does not preclude the presence of a gastric
malignancy. There have been rare reports of transient healing of gastric ulcers despite subsequently documented
Reversible confusional states have been observed on occasion, predominantly, but not exclusively, in
severely ill patients. Advancing age (50 or more years) and preexisting liver and/or renal disease appear to be
contributing factors. In some patients these confusional states have been mild and have not required discontinuation
of Tagamet therapy. In cases where discontinuation was judged necessary, the condition usually cleared within
3 to 4 days of drug withdrawal.
Carcinogenesis, Mutagenesis, Impairment of Fertility
In a 24-month toxicity study conducted in rats, at dose levels of 150, 378 and 950 mg/kg/day
(approximately 8 to 48 times the recommended human dose), there was a small increase in the incidence of benign
Leydig cell tumors in each dose group; when the combined drug-treated groups and control groups were compared, this
increase reached statistical significance. In a subsequent 24-month study, there were no differences between the rats
receiving 150 mg/kg/day and the untreated controls. However, a statistically significant increase in benign Leydig
cell tumor incidence was seen in the rats that received 378 and 950 mg/kg/day. These tumors were common in control
groups as well as treated groups and the difference became apparent only in aged rats.
Tagamet (cimetidine) has demonstrated a weak antiandrogenic effect. In animal studies this was
manifested as reduced prostate and seminal vesicle weights. However, there was no impairment of mating performance or
fertility, nor any harm to the fetus in these animals at doses 8 to 48 times the full therapeutic dose of
Tagamet, as compared with controls. The cases of gynecomastia seen in patients treated for 1 month or longer
may be related to this effect.
In human studies, Tagamet has been shown to have no effect on spermatogenesis, sperm count,
motility, morphology or in vitro fertilizing capacity.
Teratogenic Effects. Pregnancy Category B : Reproduction studies have been performed in rats,
rabbits and mice at doses up to 40 times the normal human dose and have revealed no evidence of impaired fertility or
harm to the fetus due to Tagamet. There are, however, no adequate and well-controlled studies in pregnant
women. Because animal reproductive studies are not always predictive of human response, this drug should be used
during pregnancy only if clearly needed.
Tagamet is secreted in human milk and, as a general rule, nursing should not be undertaken while a
patient is on a drug.
Clinical experience in children is limited. Therefore, Tagamet therapy cannot be recommended
for children under 16, unless, in the judgment of the physician, anticipated benefits outweigh the potential risks.
In very limited experience, doses of 20 to 40 mg/kg per day have been used.
In immunocompromised patients, decreased gastric acidity, including that produced by acid-suppressing
agents such as cimetidine, may increase the possibility of a hyperinfection of strongyloidiasis.