Attenuation of hydrochlorothiazide-induced hypokalemia in dogs by a beta-adrenergic blocking drug, timolol.

Hydrochlorothiazide, administered at 1, 3 and 9 mg/kg/day p.o. for 4 days, produced a dose-dependent lowering of plasma potassium and an elevation in plasma renin activity in unanesthetized dogs. When plasma renin activity was suppressed in diuretic-treated dogs by the potent beta-adrenergic receptor-blocking drug, timolol (0.5, 2 mg/kg/day p.o. for 4 days), the hypokalemia and hyperreninemia were significantly less pronounced. The data suggest that beta-adrenergic blocking drugs can be used to antagonize these side effects of diuretics.