Hemodynamic effects of intravenous diltiazem in hypoxic pulmonary hypertension

The short-term effects of intravenously administered diltiazem on pulmonary and systemic hemodynamics were evaluated in patients with hypoxic pulmonary hypertension. Twelve patients were randomly assigned to two groups in a double-blind fashion. One group (eight patients) received diltiazem, and the other group (four patients) received a placebo. Three increasing doses of diltiazem (0.2, 0.3, and 0.4 mg/kg of body weight) were injected into each patient, followed each time by an infusion (2 micrograms/kg/min, 3 micrograms/kg/min, and 4 micrograms/kg/min). The effects of the drug were also compared with those of oxygen, and the combined effect of high oxygen and diltiazem was tested. The mean plasma concentrations of diltiazem were, successively, 64 +/- 4, 158 +/- 19, and 267 +/- 40 ng/ml with the three increasing doses. There was no significant effect of diltiazem on the pulmonary vascular resistance even when given with oxygen. Diltiazem was well tolerated even at high doses. The arterial oxygen pressure, systemic oxygen supply, and oxygen consumption were unchanged. We conclude that diltiazem does not seem to decrease acutely hypoxic pulmonary vasoconstriction in patients with chronic hypoxia; however, diltiazem may be given safely to these patients for other indications, such as angina pectoris.