Hydrochlorothiazide × Spironolactone

Opposing effects on potassium: thiazide depletes it, spironolactone retains it. Combination in resistant hypertension and ascites. In CKD, hyperkalaemia risk rises.

With a balanced combination, no specific symptoms. Weakness, fatigue, paraesthesias, arrhythmia. Symptoms develop at potassium above 5.5 mmol/L; life-threatening above 6.5 mmol/L.

Check potassium and creatinine at 2 and 4 weeks after starting, then every 3 months. With creatinine clearance below 30 mL/min, do not prescribe spironolactone. In older patients, watch for dehydration, especially in heat or acute illness.