Question

Explain the mechanism of action of captopril. ACE inhibitors produced a dry cough as unwanted side effect. Explain the existence of a dry cough following the administration of an ACE inhibitor.

Answer 1

Captopril is a sulfhydryl containing dipeptide surrogate of proline which abolish the pressor action of A-1 but not of A-2 , it also increase the level of plasma kinin and potentiate the hypotensive action of exogenously administered bradykinin pre treatment with B2 kinin receptor antagonist has shown that kinins do contribute to the acute vasodepressor action of ACE inhibitor.

Captopril lowers BP buy in short term, magnitude of response is dependent on Na+ status and the level of renin-angiotensin activity. In normotensive Na+ replete individuals the fall in BP attending intjam few doses of ACE inhibitor is modest

The mechanism of producing dry cough is

cough results from elevated levels of bradykinin causing stimulation of small diameter sensory afferents in the lungs (type J receptors).Angiotensin-converting enzyme has been shown to be involved in the destruction of bradykinin in addition to its effects on angiotensin.

2 Inhibition of angiotensin-converting enzyme would, therefore, increase levels of bradykinin, and, in animals, this agent is known to stimulate type J receptors.

3 Excitation of these receptors may cause nonproductive cough,4 and this is consistent with the reported effects of bradykinin when inhaled by human