Results of a pilot clinical trial of sildenafil for pulmonary hypertension in sickle cell disease (SCD). Baseline measurements were made in 12 patients with SCD on hydroxyurea, and then they were treated with oral sildenafil (25 to 100 mg 3 times daily) for up to 6 months. Sildenafil therapy significantly decreased estimated pulmonary artery systolic pressure (A) and improved 6-min walk distance (B). (C) Time course of the effects of sildenafil on tricuspid regurgitant jet velocity. (D) Decrease in plasma NT-pro-BNP levels with sildenafil therapy.¹⁸