Propranolol dosage, plasma concentration, and beta blockade.

One hundred sixty-nine normal men received varying propranolol dosage regimens and placebo. Dose level and frequency were compared with plasma propranolol levels and beta blockade, as assessed by reduction of exercise tachycardia. Propranolol levels above 20 ng/ml induced significant beta blockade. An average daily propranolol dose slightly in excess of 160 mg led to a minimum plasma level above 20 ng/ml. Approximately 50% of subjects achieved 20 bpm or greater decrease in exercise tachycardia with 160 mg per day. The degree of beta blockade at the daily minimum propranolol level was related to dose and not dose frequency. The relation of propranolol dose and plasma levels to beta blockade in normal subjects appears to reflect observations in large clinical trials.