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Investigation of the safe withdrawal period for propranolol in patients scheduled for open heart surgery.

The time necessary for dissipation of radioactive labelled propranolol and its metabolites and the cardiac effects of this agent in the hearts of patients undergoing open-heart surgery were studied. Isoprenaline produced chronotropic and inotropic responses in atrial muscle in tissue bath studies which were normal 8 to 12 hours after withdrawing propranolol. After the administration of either 25 or 75 muCi of 14C-labelled propranolol, the myocardial tissue concentration declined to insignificant levels between 24 and 28 hours. We conclude that withdrawal of propranolol therapy 24 to 48 hours before cardiac surgery should be acceptable.