Plasma propranolol levels associated with suppression of ventricular ectopic beats.

The plasma propranolol levels associated with the abolition of chronic, stable ventricular ectopic beats have been studied. Racemic propranolol (DL) suppressed the ectopic foci at plasma levels of 40-85 ng/ml in eight patients, but levels of 70-200 ng/ml were unsuccessful in four patients. Dextro-(D) propranolol levels of 180-310 ng/ml were ineffective in four patients who had previously responded at levels of 60-75 ng/ml of racemic propranolol. The significance of the sympathetic nervous system in the genesis of ectopic beats is discussed. It is concluded that propranolol is clinically effective by virtue of its beta-adrenergic blocking activity.