Effects of timolol on blood pressure, systemic hemodynamics, plasma renin activity, and glomerular filtration rate in patients with essential hypertension.

Timolol, a non-cardioselective beta-blocking agent, was administered orally after 2 weeks of placebo to 14 patients with essential hypertension for 8 weeks following 1-4 weeks of dose-ranging period. Patients were first hospitalized and submitted to a diagnostic workup. They were placed on a diet containing 100 mEq of Na+ and 65 mEq of K+; this regimen was also prescribed during outpatient treatment. The changes in blood pressure, systemic hemodynamics, plasma renin activity, urine aldosterone, and glomerular filtration rate were evaluated. A significant and stable decrease in systolic and diastolic blood pressure associated with a fall in cardiac output (-21%), heart rate (-17%), plasma renin activity, and urine aldosterone were observed. The blood pressure lowering effect was unrelated to the decrease in cardiac output and plasma renin activity. Glomerular filtration rate was unchanged. No important side effects were observed during the treatment.