Various drugs are implicated in gynecomastia and can be classified into the following categories:
- Estrogens or drugs with estrogen like activity such as diethylstilbestrol, digitalis, phytoestrogens, and estrogen-contaminated food and estrogen-containing cosmetics
- Drugs that enhance estrogen synthesis such as gonadotropins, clomiphene, phenytoin, and exogenous testosterone
- Drugs that inhibit testosterone synthesis or action such as ketoconazole, metronidazole, alkylating agents, cisplatin, spironolactone, cimetidine, flutamide, finasteride, and etomidate
- Drugs that act by unknown mechanisms such as isonicotinic acid hydrazide, methyldopa, busulfan, tricyclic antidepressants, diazepam, penicillamine, omeprazole, phenothiazines, calcium channel blockers, ACE inhibitors, alcohol, marijuana, and heroin
- Drugs in the same class do not all cause gynecomastia to the same extent
