The FDA recently approved Pfizer's Revatio (sildenafil citrate) for the treatment of pulmonary arterial hypertension (PAH). The drug contains the same active ingredient as Viagra, which treats erectile dysfunction. The rare disease, PAH, is characterized by a sustained arterial blood pressure of more than 25 mm Hg at rest or more than 30 mm Hg during exercise. (The normal range is between 12 and 16 mm Hg at rest.) Sildenafil affects pulmonary blood vessels the same way it affects penile vessels?by inhibiting cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type-5 in the smooth muscle of the pulmonary vasculature. An increased cGMP results in relaxation, and, in patients with pulmonary hypertension, the effect may be vasodilation of the pulmonary vascular bed. The clinical trial included 277 patients receiving 20, 40, or 80 mg of Revatio tid. The result was an average increase in 6-minute walking distance of 147 feet?significantly better than that of the placebo group. Revatio is indicated for patients with idiopathic PAH; PAH caused by lung or heart disease, HIV infection, or scleroderma; and pulmonary hypertension in newborns. It is the first medication approved for use in the early stages of PAH. The recommended dose of Revatio is 20 mg tid with or without food. Side effects with Revatio are similar to those with Viagra: headache, flushing, dyspepsia, and insomnia.
Ms. Farley is a freelance medical writer based in Wakefield, RI.
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