Effects of labetalol and methyldopa on renal function.

Renal function studies were performed in subjects with mild hypertension treated with labetalol (n = 5) and moderate to moderately severe hypertension treated in a random double-blind fashion with either labetalol (n = 6) or methyldopa (n = 6). Drugs were given in doses sufficient to reduce standing diastolic blood pressure to less than 90 mm Hg. This was achieved in all subjects without significant side effects. Inulin clearance, para-aminohippurate clearance, filtration fraction, free-water clearance, and maximal concentrating ability was assessed before and after 15 days of drug. No alterations in any parameter were noted with labetalol. Inulin clearance fell by 13% (p less than 0.05), and filtration fraction fell from 0.23 to 0.18 (p less than 0.02), but other parameters of renal function did not change with methyldopa.