The effect of penbutolol on glomerular filtration

Penbutolol, a new beta-adrenoceptor blocker, was found to increase the glomerular filtration rate (GFR) significantly (16%) relative to placebo when administered orally in a dose of 40 mg daily for 7 consecutive days to healthy males. Measurements were performed after the seventh dose. In contrast, a single acute intravenous dose of penbutolol 4 mg did not influence the GFR, which was determined by means of a gamma counter after intravenous injection of technetium-99m diethylenetriaminepenta-acetic acid. Since penbutolol possesses moderate beta-adrenomimetic activity, it is postulated that the observed increase in the GFR after oral penbutolol could be due to increased cardiac output at rest.