Studies of the mechanism of angiotensin-converting enzyme (ACE) inhibitor-associated angioedema: the effect of an ACE inhibitor on cutaneous responses to bradykinin, codeine, and histamine.

To understand better the mechanism of angiotensin-converting enzyme (ACE) inhibitor-associated angioedema, we studied the effects of ACE-inhibitor treatment on wheal-and-flare responses to histamine, codeine, and bradykinin in 10 normal subjects. No change in the size of wheal-and-flare reactions to histamine occurred, but the size of wheal reactions to codeine and bradykinin increased in all study subjects after ingesting the ACE inhibitor, captopril. Five of 10 study subjects developed flushing reactions after ACE-inhibitor treatment. We conclude that inhibition of bradykinin metabolism by ACE inhibitors is the probable cause of ACE inhibitor-related angioedema and that substance P is not the predominant mediator in this process.