Detailed Drug Information:

DRUG CLASS AND MECHANISM: It has been estimated that impotence affects 140 million men worldwide. Over half of all men with impotence arethought to have some physical (medical) cause. The remainder are believedto have psychogenic causes of impotence. Medical causes of impotenceinclude diabetes and circulatory, neurological or urological conditions.

Penile erection is caused by the engorgement of the penis with blood.This engorgement occurs when the blood vessels delivering blood to thepenis increase the delivery of blood and the blood vessels carrying bloodaway from the penis decrease the removal of blood. Under normalconditions, sexual stimulation leads to the production and release ofnitric oxide in the penis. Nitric oxide then activates the enzyme,guanylate cyclase, which causes the production of cyclic guanosinemonophosphate (cGMP). It is the cGMP that is primarily responsible for theerection by affecting the amount of blood that the blood vessels deliverand remove from the penis.

Sildenafil inhibits an enzyme called phosphodiesterase-5 (PDE5) whichdestroys the cGMP. Thus, sildenafil prevents the destruction of cGMP andallows cGMP to accumulate and persist longer. The longer cGMP persists,the more prolonged the engorgement of the penis.

PREPARATIONS: Blue, film-coated rounded-diamond- shaped tablets:25 mg, 50 mg and 100 mg.

STORAGE: Tablets should be kept at room temperature, 15-30°C(59-86°F).

PRESCRIBED FOR: Sildenafil is used for the treatment of erectiledysfunction of either organic (medical condition) or psychogenic(psychological) cause.

DOSING: Sildenafil is rapidly absorbed. Maximum observed plasmaconcentrations are reached within 30 to 120 minutes (median 60 minutes) oforal dosing in the fasted state. When sildenafil is taken with a high fatmeal, the rate of absorption is reduced, with an average delay in the timeto maximal concentration of 1 hour.

DRUG INTERACTIONS: Sildenafil increases the effectsof the blood pressure lowering medications. It also increases the blood pressure lowering effects of nitrates, e.g. isosorbide dinitrate(Isordil), isosorbide mononitrate (Imdur, Ismo, Monoket), nitroglycerin (Nitro-Dur, Transderm-Nitro) that are used primarily for treating angina. Patients taking nitrates should not receivesildenafil.

Cimetidine (Tagamet), erythromycin, ketoconazole (Nizoral), itraconazole (Sporanox) and mibefradil (Posicor) can cause marked increases in theamount of sildenafil in the body. Patients taking these medications shouldbe observed carefully if sildenafil is used.

It is expected that rifampin will decrease blood levels of sildenafiland probably reduce its effectiveness.

PREGNANCY: Although extensive testing in animals hasdemonstrated no negative effects on the fetus, sildenafil has not beenstudied in pregnant women. There is no effect on sperm count or motilityof sperm in men.

NURSING MOTHERS: It is not known whether sildenafil is excreted into breast milk.

SIDE EFFECTS: Approximately 15% of persons taking sildenafilexperience side effects. The most common side effects are facial flushing(1 in 10), headaches (1 in 6), stomach pain, nasal congestion, nausea,diarrhea, and an inability to differentiate between the colors green andblue.