Use with caution in persons who will be exposed to extreme heat, organophosphorus insecticides, and in persons receiving atropine or related drugs. Although disturbances such as galactorrhea, amenorrhea, gynecomastia and impotence have been reported, the clinical significance of elevated serum prolactin levels is unknown for most patients. An increase in mammary neoplasms has been found in rodents after chronic administration of neuroleptic drugs. Chromosomal aberrations in spermatocytes and abnormal sperm have been demonstrated in rodents treated with certain neuroleptics. Chlorpromazine diminishes the effect of oral anticoagulants.
Phenothiazines can produce alphaadrenergic blockade.
Potentiation of anticonvulsant effects does not occur. However, it has been reported that chlorpromazine may interfere with the metabolism of phenytoin and thus precipitate phenytoin toxicity. Concomitant administration with propranolol results in increased plasma levels of both drugs. Thiazide diuretics may accentuate the orthostatic hypotension that may occur with phenothiazines. Drugs which lower the seizure threshold, including phenothiazine derivatives, should not be used with metrizamide.