Comparison of the effects of labetalol and hydrochlorothiazide on the ventilatory function of hypertensive patients with mild chronic obstructive pulmonary disease.

Labetalol is a new adrenergic antagonist with both alpha- and beta-blocking effects. The effects of labetalol and hydrochlorothiazide on the hypertension and ventilatory function of patients with both hypertension and mild reversible chronic pulmonary disease were compared. In this double-blind study, 20 patients were randomly allocated to receive increasing doses of labetalol (100 to 400 mg three times a day) or hydrochlorothiazide (25 to 50 mg three times a day) over a four-week treatment period. Patients returned at weekly intervals for spirometry baseline, two hours after receiving the medication for the following week, and five minutes after an exercise test. Each treatment reduced the blood pressure significantly and to a comparable degree. There was no significant decrease in ventilatory function two hours after administration of the drug at any visit for either drug. Ventilatory function did not deteriorate significantly following exercise with either drug. With labetalol there was a progressive statistically significant decline in baseline forced expiratory volume in one second from 1,860 +/- 190 ml to 1,685 +/- 190 ml during the four-week study period, although no patient became symptomatic from shortness of breath. We conclude that labetalol is an effective antihypertensive agent that does not adversely effect ventilatory function immediately, but that may lead to a decline in ventilatory function when administered long-term.