In 10 patients with precapillary pulmonary hypertension due to pulmonary fibrosis, the arterial blood pressure, right heart hemodynamics, cardiac output, and arterial oxygen partial pressure were measured to evaluate the benefits of acute sublingual (5 mg) nitrendipine. Additionally, the effect of oxygen enriched air was compared to control. At rest, nitrendipine significantly diminished arterial blood pressure [102 +/- 3 to 93 +/- 3 mm Hg (mean +/- SEM)], right atrial pressure (5.7 +/- 0.9 to 3.4 +/- 0.8 mm Hg), mean pulmonary artery pressure (33.4 +/- 3.5 to 29.8 +/- 3.3 mm Hg), and pulmonary artery wedge pressure (13.0 +/- 2.0 to 6.8 +/- 0.8 mm Hg). During exercise, nitrendipine reduced mean pulmonary artery pressure (54.5 +/- 4.8 to 49.3 +/- 4.7 mm Hg) and right atrial pressure (9.3 +/- 1.3 to 6.8 +/- 1.4 mm Hg). A diminuation of arterial partial oxygen pressure did not occur at rest (63.2 +/- 3.8 mm Hg) or during exercise (50.9 +/- 5.1 mm Hg). Thus, nitrendipine causes a slight but significant improvement of right heart hemodynamics. The occurrence of arteriovenous intrapulmonary shunting due to vasodilatating effects of nitrendipine can be excluded. Also, nitrendipine can safely be used in combined arterial hypertension and pulmonary fibrosis.