A Cochrane review included four studies on the clinical efficacy of the vasodilator sildenafil in patients with pulmonary hypertension, with a total of 77 subjects. Two studies assessed the acute effects of sildenafil. Two small crossover study assessed the effects of long term administration. The 'acute effect' studies indicated that sildenafil has a pulmonary vasodilatory effect. The two crossover studies showed improvement in symptoms. One study showed improvement in fatigue domains from a validated health status questionnaire. Both crossover studies reported that the drug was well tolerated.
In a multicenter RCT , 278 patients were assigned to placebo or sildenafil (20, 40, or 80 mg) orally 3 times daily for 12 weeks. Sildenafil significantly improved exercise capacity, as assessed according to the six-minute walking test (6MW test). The 6MW test increased from baseline in all sildenafil groups, with mean placebo-corrected treatment effects of 45, 46, and 50 m for 20-, 40-, and 80-mg doses of sildenafil, respectively (P<0.001 for all comparisons). All sildenafil doses reduced the mean pulmonary-artery pressure (P=0.04, P=0.01, and P<0.001, respectively), and improved the WHO functional class (P=0.003, P<0.001, and P<0.001, respectively). The incidence of clinical worsening did not differ significantly between the patients treated with sildenafil versus placebo. Long-term data (available only at a dose of 80 mg 3 times daily) in 222 patients completing 1 year of treatment with sildenafil monotherapy showed sustained improvement from baseline at 1 year in the 6MW test (51 m).
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