To the Editor.— I found interesting the comprehensive discussions by Martin D. Valentine, MD, and David M. Kornhauser, MD, concerning the modification of the anaphylactic response by propranolol (1981;245:1767). I would like to add to the discussion the possibility of a drug interaction between epinephrine and propranolol.1,2This combination has led to bradycardia and arteriovenous block. By blocking the β receptors, propranolol allows unopposed a stimulation by epinephrine. Bradycardia probably results from a vagal reflex to the resulting hypertension. This possibility must be considered if epinephrine is administered to a patient receiving a β-blocker.