sildenafil, Viagra, Revatio (cont.)

Pharmacy Author:
Medical and Pharmacy Editor:

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

PRESCRIPTION: Yes

GENERIC AVAILABLE: No

PREPARATIONS: Viagra is a blue, film-coated, rounded, diamond-shaped tablet that comes in 25, 50, and 100 mg tablets for treating impotence. Revatio comes in a 20 mg tablet and is used for treating pulmonary arterial hypertension.

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

PRESCRIBED FOR: Sildenafil is used for the treatment of erectile dysfunction of either organic (medical condition) or psychogenic (psychological) cause and for pulmonary arterial hypertension.

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

DRUG INTERACTIONS: Sildenafil increases the effects of the blood pressure lowering medications. It also increases the blood pressure lowering effects of nitrates, for example, 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 receive sildenafil.

Patients should not combine sildenafil with Revatio (another form of sildenafil) or other PDE5 inhibitors (for example, vardenafil [Levitra], tadalafil [Cialis]).

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



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