Anti-Impotency Drugs: Impotence or erectile dysfunction (ED) is the inability of a male to achieve satisfactory erection of the penis for sexual intercourse. Estimates of its prevalence are difficult to make, but the problem is not uncommon, specially in the order male. The causes of impotence may be psychological (stress, mental depression, anxiety about sexual performance); or organic (hypogonadism, neurological dysfunction, injury diabetes mellitus, peripheral vascular disease, and penile abnormal like Peyronie’s disease, microphallus); or drug-induced.

Phentolamine and Papaverine
The combination of the alpha-adrenoceptor blocker phentolamine (2 mg) with the nonspecific vasodilator papaverine (12—40 mg) when injected into the corpora cavernosa of the penis causes erection in men suffering from erectile dysfunction. The long-term efficacy of this therapy is not known. There is a risk of local fibrotic reactions on prolonged use.

Aiprostadil 
Intracavernosal injection of the vasodilator aiprostadil (PGE is used to produce penile erection in men with ED. Doses of 0.2 to 140 mcg are used. Penile pain occurs frequently as PGE derivatives have algesic effects.

Sildenafil Citrate (Viagra)
Viagra is the first oral pill to treat erectile dysfunction (ED). It is popular known as the “little blue pill” or “the virility pill".
Sildenafil does not directly cause erections, but effects the r to sexual stimulation. It enhances the smooth muscle relaxant effect of nitric oxide (NO), a critical second messenger released in the corpora cavernosa in response to sexual stimulation. Both phentolamine and sildenafil counteract the defective functioning of NO in the penile tissue by amplifying signals at the nerve endings.