PIP: The number of persons with drug induced sexual dysfunction has risen simultaneously with the unending increase in the number of commercially available drugs. Sexual dysfunction may seriously impair the human psyche. Patients do not often admit to sexual dysfunction, however, so physicians often miss the symptoms entirely. In addition, they may attribute them to other causes, such as depression. Drugs disrupt all 3 neurophysiologic phases of sexual response (desire, excitement, and orgasm), especially in men, either causing a decrease or loss of libido, impotence (the most common symptom), or failure of ejaculation or anorgasmia. The mechanisms involved are not well understood. Researchers do know, however, that the drug cimetidine (Tagamet) blocks androgen receptors, decreases testosterone synthesis, and induces higher circulating levels of estradiol resulting in impotence and breast enlargement in men. Antihypertensive drugs have a higher frequency of causing sexual dysfunction, particularly impotence, than other drugs. Some also induce or worsen depression that can in turn cause or intensify sexual dysfunction. Both legal and illegal psychoactive drugs act on multiple sites thus often stimulating sexual dysfunction. Further, some hormonal drugs also induce sexual side effects, such as norethindrone and progesterone. Physicians who prescribe a drug associated with sexual side effects should inform patients about their possible occurrence and recommend that they be aware of the symptoms. They should ask these patients do not usually offer this information themselves. If sexual dysfunction develops, physicians can reduce the dosage or switch to an alternative drug. At that time, they should express optimism that the sexual dysfunction will cease.