Spironolactone is effective for NYHA class III and IV heart failure and hypertension (4th or 5th line) but can be a difficult drug to use. Elevated serum potassium levels may occur in around 18% of patients.
In a case-control study spironolactone was associated with a doubling in the rate of gastrointestinal bleed events.1 This effect was stronger with increasing doses and when spironolactone was combined with NSAIDs/corticosteroids.
Medicines & Healthcare products Regulatory Agency (UK) now advise that “use of spironolactone with ACEi or ARB increases the risk of severe hyperkalaemia, particularly in patients with marked renal impairment, should be used with caution”, and requires regular monitoring of renal function.2
Spironolactone should only be started if serum potassium ≤5.0mmol/L and serum creatinine is ≤221 μmol/L. Monitor serum potassium and creatinine 1 week after initiation or increase in dose of spironolactone, monthly for the first 3 months, then quarterly for a year, and then every 6 months.