Relationships among timolol doses, plasma concentrations and beta- adrenoceptor blocking activity.

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Abstract
The relationships among dose, plasma concentration and .beta.-adrenoceptor blockade after single and repeated doses (0.5-20 mg) of timolol [an antihypertensive] and placebo were studied in 6 normal men. Maximal suppression of exercise-induced tachycardia (bicycle ergometry) was dose-dependent and greater at 2 than at 6 h after dosing; activity up to 12 h was evident on the last dosing day. Attenuation of exercise-induced tachycardia was strongly correlated with the timolol dosage over the 0.5 to 5-10 mg range. A plasma timolol concentration of 27 ng/ml was associated with maximal suppression of exercise-induced tachycardia. Suppression of exercise-induced tachycardia and areas under the plasma concentration-time curves did not differ significantly on the 1st and last dosing days.