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(sildenafil, Pfizer Inc.)

A phosphodiesterase type 5 (PDE5) inhibitor for treating pulmonary arterial hypertension (WHO group I) to improve exercise ability. The second oral therapy approved for PAH; the first was the endothelial receptor antagonist Tracleer (bosentan). Other treatments come in intravenous, subcutaneous, or inhaled forms. Marketed as Viagra for erectile dysfunction.

* Recommended Dosage: 20 mg three times a day, 4-6 hours apart.

* Special Considerations: Labeling notes that efficacy of Revatio has not been evaluated in patients currently on Tracleer. In the trial that led to approval, Revatio was well tolerated, with side effects that were mostly mild to moderate in severity and no clinically significant changes in laboratory parameters. One patient on the highest dose stopped treatment due to treatment-related headache, flushing, and dyspepsia.

* Comment: That trial compared three doses of Revatio (20 mg, 40 mg, or 80 mg t.i.d.) with placebo in 277 patients with PAH; most had idiopathic PAH, which is relatively rare and usually fatal in 1-2 years. Others had more common forms of PAH, associated with connective tissue disorders such as lupus or scleroderma (30%) or occurring after surgical repair of congenital systemic-to-pulmonary shunts (6%).

After 12 weeks, patients with any kind of PAH on any dose were able to walk a mean of 45-50 meters farther in a 6-minute walk test than those on placebo, a highly significant difference. The drug also was associated with improvements in mean pulmonary artery pressure, pulmonary vascular resistance, cardiac output, and mixed venous oxygen saturation, compared with baseline and with placebo, said Lewis J. Rubin, M.D., who reported the results in a poster presentation at the annual meeting of the American Society of Hypertension. Dr. Rubin, professor of medicine at the University of California, San Diego, received grant funding and was paid as a consultant to Pfizer for the study.

Sildenafil inhibits PDE5 in the smooth muscle of the pulmonary vasculature, promoting accumulation of intracellular cyclic guanosine monophosphate, which can promote vasodilation of the pulmonary vascular bed.

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Title Annotation:NEW & APPROVED
Author:Mechcatie, Elizabeth
Publication:Internal Medicine News
Geographic Code:1USA
Date:Jul 15, 2005
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