Erectile dysfunction is caused by:-

Drugs causing erectile dysfunction. Diuretics Thiazides Antihypeensives Beta blockers Calcium channel blockers Cardiac drugs Gemfibrozil Clofibrate Antidepressants SSRI TCA MAO inhibitors H2 antagonists Cimetidine Hormones GnRH agonists 5 alpha reductase inhibitors Others Ethanol Cocaine Marijuana Cimetidine (but not other H2 blockers) has antiandrogenic action (displaces dihydrotestosterone from its cytoplasmic receptor), increases plasma prolactin and inhibits degradation of estradiol by liver. High doses given for long periods have produced gynaecomastia, loss of libido, impotence and temporary decrease in sperm count.