Angiotensin Converting Enzyme Inhibitors
ACE inhibitors prevent the conversion of angiotensin I to angiotensin II by angiotensin converting enzyme (ACE) in the lungs, in turn reducing effects of angiotensin II. These effects include:
- Vasoconstriction
- Noradrenaline reuptake inhibition
- Thirst
- ADH release
- ACTH release
- Aldosterone release
- Reduces Kf, reducing GFR
Indications
- Hypertension
- Particularly in insulin dependent diabetes with diabetic nephropathy
- Less effective for this indication in the black population
- Contribute to post-operative hypertension and may be withheld perioperatively
- Cardiac failure
All grades.
- MI with LV dysfunction
Improved prognosis.
Classification
Can be divided into three groups based on pharmacokinetics:
- Active drug with active metabolites
Captopril. - Prodrug
Ramipril. - Not metabolised and excreted unchanged in urine
Lisinopril.
Common Features of ACE Inhibitors
| Property | Drug |
|---|---|
| Resp | Bradykinin cough |
| CVS | ↓ SVR and BP. Unaffected HR and baroreceptor response. |
| Endocrine | Hypoglycaemia in diabetics |
| Renal | With a normal renal perfusion pressure, natriuresis results. However, a fall in renal perfusion pressure may cause pre-renal failure (e.g. renal artery stenosis). |
| Haeme | Agranulocytosis, thrombocytopenia |
| Immune | Angioedema |
| Metabolic | ↑ Renin release. |
| Interactions | ↓ Aldosterone release, which ↑ the efficacy of spironolactone and may precipitate hyperkalaemia. Pharmacodynamic interaction with NSAIDs to drop renal perfusion pressure. |
References
- Peck TE, Hill SA. Pharmacology for Anaesthesia and Intensive Care. 4th Ed. Cambridge University Press. 2014.