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 secondary prevention of ischaemic heart disease.

Mechanism of action

Inhibit the conversion angiotensin I to angiotensin II

Adverse 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


  • 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*.

*Renal Association UK, Clinical Knowledge Summaries quote 50% which seems rather high. SIGN advise that the fall in eGFR should be less than 20%. The NICE CKD guidelines suggest that a decrease in eGFR of up to 25% or a rise in creatinine of up to 30% is acceptable