The effects of long term methyldopa in patients with hypoxic cor pulmonale

Methyldopa (alpha-methyldopa) was given to patients with cor pulmonale secondary to chronic obstructive airways disease (COAD) to determine its effect on pulmonary haemodynamics. Twenty-five patients were randomly allocated to methyldopa (750 mg daily) or placebo. Pulmonary haemodynamics were measured twice, 12 months apart. Conventional therapies were continued unchanged.

The effects of the drug on pulmonary haemodynamics were inconclusive when considered overall, but total pulmonary vascular resistance (TPVR) fell in all patients on active therapy in whom measurements were obtained both at rest and upon exercise. Only one patient in the placebo group achieved this. Over the trial period there was one death in the active but five in the placebo group. Survival was unrelated to abnormalities in pulmonary haemodynamics at the commencement of the trial in this study although the numbers of patients was small. Postural hypotension developed in patients receiving methyldopa and limited the dose that could be administered.

The problems involved in long term trials of vasodilators in hypoxic cor pulmonale are discussed.