Comparison of effectiveness of timolol administered once a day and twice a day in the control of blood pressure in essential hypertension.

The effects of a single dose and of two equally divided doses of timolol were compared in a double-blind trial in 15 patients with essential hypertension. The amount of timolol per day remained constant for each patient, but individual patients received different amounts (from 10 mg to 30 mg/day). Timolol combined with a diuretic produced similar lowering of blood pressure in patients who required 10 mg, 20 mg or 30 mg of timolol per day when given either as one dose or in two equal doses. Plasma concentrations of timolol were high enough to be a major contributing factor to the long duration of the hypotensive response.