Combination therapy with oral sildenafil and inhaled iloprost for severe pulmonary hypertension. Sildenafil for treatment of lung fibrosis and pulmonary hypertension: a randomised controlled trial. The efficacy and tolerability of sildenafil in patients with moderate-to-severe pulmonary hypertension.
Inhalation of the stable prostacyclin analogue iloprost is being studied for treatment of pulmonary hypertension. The selective phosphodiesterase-5 inhibitor sildenafil has been reported to cause pulmonary vasodilatation.
                To evaluate the safety and effectiveness of oral sildenafil, alone and in combination with inhaled iloprost, for treatment of pulmonary hypertension.
                Randomized, controlled, open-label trial.
                Intensive care unit.
                30 patients with severe pulmonary arterial hypertension (n = 16), chronic thromboembolic pulmonary hypertension (n = 13), or pulmonary hypertension due to aplasia of the left pulmonary artery (n = 1), all classified as New York Heart Association class III or IV.
                All patients received inhaled nitric oxide and aerosolized iloprost (inhaled dose, 2.8 microg). They were then randomly assigned to receive 12.5 mg of oral sildenafil, 50 mg of sildenafil, 12.5 mg of sildenafil plus inhaled iloprost, or 50 mg of sildenafil plus inhaled iloprost.
                Systemic and pulmonary arterial pressure, pulmonary arterial occlusion pressure, cardiac output, central venous pressure, peripheral arterial oxygen saturation, and arterial and mixed venous blood gases were measured during right-heart catheterization by using a Swan-Ganz catheter.
                In rank order of pulmonary vasodilatory potency (maximum reduction of pulmonary vascular resistance and increase in cardiac index), 50 mg of sildenafil plus iloprost was most effective, followed by 12.5 mg of sildenafil plus iloprost. Iloprost alone and 50 mg of sildenafil were almost equally effective but were less potent than the combination regimens, and the least potent treatments were 12.5 mg of sildenafil and nitric oxide. In patients who received 50 mg of sildenafil plus iloprost, the maximum change in pulmonary vasodilatory potency was -44.2% (95% CI, -49.5% to -38.8%), compared with -14.1% (CI, -19.1% to -9.2%) in response to nitric oxide. With administration of 50 mg of sildenafil plus iloprost, the area under the curve for reduction in pulmonary vasodilatory resistance surpassed that of administration of 50 mg of sildenafil alone and iloprost alone combined, the vasodilatory effect lasted longer than 3 hours, and systemic arterial pressure and arterial oxygenation were maintained. No serious adverse events occurred.
                Although limited by the small sample and lack of long-term observations, the study shows that oral sildenafil is a potent pulmonary vasodilator that acts synergistically with inhaled iloprost to cause strong pulmonary vasodilatation in both severe pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. Lung fibrosis can be complicated by pulmonary hypertension, limiting exercise tolerance and life expectancy. Furthermore, vasodilators might cause deterioration in gas exchange. Our aim was to compare acute effects of sildenafil, nitric oxide, and epoprostenol in individuals with pulmonary hypertension secondary to lung fibrosis.
                We did a randomised controlled, open-label trial, in 16 individuals admitted to our hospital with pulmonary hypertension secondary to lung fibrosis. After inhalation of nitric oxide (10-20 ppm), we assigned patients to either maximum tolerated dose of intravenous epoprostenol (mean 8.0 ng/kg per min; n=8) or oral sildenafil (50 mg; n=8). Our primary objective was to assess pulmonary vasodilative potency (decrease in pulmonary vascular resistance index) of sildenafil by comparison with inhaled nitric oxide and infused epoprostenol. Analyses were by intention to treat.
                Pulmonary vascular resistance index was reduced by nitric oxide (-21.9%, 95% CI -14.1 to -36.2), epoprostenol (-36.9%, -24.4 to -59.6), and sildenafil (-32.5%, -10.2 to -54.1). However, ratio of pulmonary to systemic vascular resistance decreased only in individuals who received nitric oxide and sildenafil. Baseline measurement of multiple-inert-gas elimination showed right-to-left shunt flow (4.8%, 0.0-28.2) and little perfusion of low ventilation(V)/perfusion(Q) areas (0.1%, 0.0-13.0). Prostacyclin increased V/Q mismatch (shunt 16.8%, 10.8-35.9; low V/Q 3.8%, 0.0-13.0) and decreased arterial oxygenation. By contrast, nitric oxide (4.5%, 0.0-18.0; 0.0%, 0.0-17.3) and sildenafil (3.3%, 0.0-11.3; 0.0%, 0.0-12.4) maintained V/Q matching, with raised arterial partial pressure of oxygen (14.3 mm Hg, -1.7 to 31.3) noted for sildenafil. We recorded no adverse events.
                Sildenafil causes preferential pulmonary vasodilation and improves gas exchange in patients with severe lung fibrosis and secondary pulmonary hypertension. Pulmonary arterial hypertension is a life-threatening disease for which continuous intravenous infusion of prostacyclin has proved effective. However, it carries the risk of serious complications arising from the complex delivery system. Prostacyclin analogs, endothelin antagonists, and the phosphodiesterase-5 inhibitor sildenafil are emerging promising therapies. This study was aimed at evaluating the utility of oral sildenafil in patients with pulmonary hypertension of varied etiology, poorly controlled on conventional treatment.
                Ten consecutive patients with pulmonary hypertension, either primary or related to previous left-to-right shunts, thromboembolism, or interstitial lung disease, poorly controlled on conventional therapy such as warfarin, calcium antagonists, digitalis, and diuretics, were included. A thorough clinical, laboratory, and comprehensive echo Doppler evaluation was performed before enrollment in the trial to establish the diagnosis and obtain baseline data. Subjects received sildenafil 25 mg 8 hourly, or a matching placebo for two weeks each, in a randomized, double-blind, crossover design. A run-in period of two weeks was permitted between the two therapies during which patients continued to receive the conventional therapy without any vasodilator. At the end of each therapy period, the patients were evaluated for symptoms, New York Heart Association class, distance covered during the 6 min walk test, rating of modified Borg dyspnea score, and systolic pulmonary artery pressure using echo Doppler. The differences in the above variables at the end of sildenafil and placebo therapies were compared. Nine patients completed the study protocol. Sildenafil, compared to placebo, was associated with improved exercise tolerance as determined by the 6 min walk test (266.67+/-131.45 m v. 170+/-105 m; p<0.005), decrease in modified Borg dyspnea score (3.56+/-1.01 v. 5.11+/-1.45; p<0.01), decrease in Doppler-estimated pulmonary artery systolic pressures (55.33+/-16.52 mmHg v. 75.33+/-19.75 mmHg; p<0.005), improvement in New York Heart Association class (2 patients), and improvement in symptoms. Sildenafil was well tolerated with no untoward effects; further, no significant changes in heart rate or blood pressure occurred during the study period.
                Sildenafil improves exercise capacity and symptoms, and decreases pulmonary artery pressures in patients with primary or secondary pulmonary hypertension of varied etiology.
The validity of the observed effects is undermined by small participant numbers and inadequate exploration of the different disease etiologies. The effects on long term outcome such as NYHA functional class, symptoms, mortality and exercise capacity require further validation. More studies of adequate size are required before the long term effects of sildenafil on clinically important outcomes can be established.