Erectile dysfunction therapy drugs
Erectile dysfunction therapy drugs treat penile erectile dysfunc-tion that results from a lack of blood flowing through the corpus cavernosum. This type of erectile dysfunction usually stems from vascular and neurologic conditions. Drugs used for erectile dys-function include alprostadil, sildenafil, tadalafil, and vardenafil.
Erectile dysfunction drugs are well absorbed in the GI tract. Dis-tribution of these drugs isn’t known. The majority of these drugs—including sildenafil, tadalafil, and vardenafil—are given orally, metabolized in the liver, and excreted in feces.
Alprostadil is the exception: it’s administered directly into the cor-pus cavernosum, metabolized in the lungs, and excreted in urine.
Sildenafil, tadalafil, and vardenafil selectively inhibit the phospho-diesterase type 5 receptors, which causes an increase in blood lev-els of nitric oxide. This increase in nitric oxide levels activates the cGMP enzyme, which relaxes smooth muscles and allows blood to flow into the corpus cavernosum, causing an erection.
Alprostadil acts locally, promoting smooth muscle relaxation, which causes an increase in blood flow to the corpus cavernosum and produces an erection.
Alprostadil, sildenafil, tadalafil, and vardenafil are all used in the treatment of erectile dysfunction. Sildenafil is also indicated for the treatment of pulmonary arterial hypertension.
Erectile dysfunction drugs may interact with other drugs in the following ways:
§ Nitrates and alpha-adrenergic blockers used in combi-nation with erectile dysfunction drugs may cause severe hypotension and potentially serious cardiac events. (See Adverse reactions to erectile dysfunction drugs.)
§ Ketoconazole, itraconazole, and erythromycin may re-sult in increased levels of vardenafil or tadalafil.
§ Protease inhibitors, such as indinavir or ritonavir, may cause increased tadalafil or vardenafil levels.