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ACE
inhibitors
- block bradykinin kinase as well as ACE and increase the concentration of
bradykinin (potent vasodilator)
- do not cause reflex tachycardia. Distinct advantage over direct vasodilators
Clinical uses
- hypertension. Particularly effective in renovascular hypertension but also
effective in anephric patients and in low renin hypertension; probably the
result of local effects on tissue ACE
- chronic heart failure: results in improved prognosis as well as improved
symptom control
- post MI in all patients who have had pulmonary oedema in association with MI,
however transient. Thought to relate to an effect on ventricular remodelling
Contraindications
- bilateral renal artery stenosis or stenosis in a solitary kidney
Captopril
- contains as sulphydryl group that interacts with Zn2+ of ACE
binding site with greater affinity than angiotensin I
- given sublingually has an onset of action in 20-30 min with maximum effect
after approx 50 min and duration of action of about 4 h
- adverse effects include agranulocytosis, Stevens-Johnson
Enalapril
- sulphydryl group of captopril substituted by phenylalanine
- pro-drug which is metabolized in liver to enalaprilat
Enalaprilat
- active metabolite of enalapril
- available as an IV preparation
- IV dose 1-5 mg. Decrease in patients with renal impairment, renovascular
hypertension and those on diuretics
- onset of action 15 min after IV administration with duration of 6-12 h
- hypotensive response is variable and is partly dependent on intravascular
volume
- excreted by kidney
Further reading
Chui PT, Low JM. Acute hypertension and vasodilators. In Oh TE (ed),
Intensive Care Manual, 4th Ed., Butterworth Heinemann, Oxford, 1997, pp 153-62
© Charles Gomersall December 1999
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