Captopril × Spironolactone

Captopril (ACE-I) reduces aldosterone synthesis, while spironolactone directly blocks aldosterone receptors. Both retain potassium. In chronic kidney disease and older patients, severe hyperkalaemia risk reaches 10–15% in the first weeks.

Muscle weakness, paraesthesia in the limbs, slowed pulse, arrhythmias. ECG shows peaked T waves and widened QRS. Severe cases progress to cardiac arrest. Symptoms typically appear within 1–2 weeks of starting the combination.

The combination is appropriate in heart failure. Check potassium and creatinine 1 week after start, then monthly. If potassium exceeds 5.5 mmol/L, reduce the spironolactone dose; above 6.0 mmol/L, stop one of the drugs.