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ACE Inhibitors

Angiotensin-converting enzyme (ACE) inhibitors are now the established first-line treatment in younger patients with hypertension and are also extensively used to treat heart failure. They are known to be less effective in treating hypertensive Afro-Caribbean patients. ACE inhibitors are also used to treat diabetic nephropathy and have a role in the secondary prevention of ischaemic heart disease.

Mechanism of action:

  • inhibit the conversion angiotensin I to angiotensin II
  • ACE inhibitors are activated by phase 1 metabolism in the liver

Side-effects:

  • cough
    • occurs in around 15% of patients and may occur up to a year after starting treatment
    • thought to be due to increased bradykinin levels
  • angioedema: may occur up to a year after starting treatment
  • hyperkalaemia
  • first-dose hypotension: more common in patients taking diuretics

Cautions and contraindications

  • pregnancy and breastfeeding - avoid
  • renovascular disease - may result in renal impairment
  • aortic stenosis - may result in hypotension
  • hereditary of idiopathic angioedema
  • specialist advice should be sought before starting ACE inhibitors in patients with a potassium >= 5.0 mmol/L

Interactions

  • patients receiving high-dose diuretic therapy (more than 80 mg of furosemide a day)
    • significantly increases the risk of hypotension

Monitoring

  • urea and electrolytes should be checked before treatment is initiated and after increasing the dose
    • a rise in the creatinine and potassium may be expected after starting ACE inhibitors
    • acceptable changes are an increase in serum creatinine, up to 30% from baseline and an increase in potassium up to 5.5 mmol/l.
    • significant renal impairment may occur in patients who have undiagnosed bilateral renal artery stenosis

Flow chart showing the management of hypertension as per current NICE guideliness