In a retrospective study of 201 patients, who had primary aldosteronism (PA), were treated between 2000 and 2020, four patients (3 men and 1 woman, aged: 54-74 years) were described, who developed hyperkalaemia during treatment with amiloride or spironolactone for PA.All four patients, who had PA, were treated with spironolactone 75-150mg daily. Dosage of spironolactone was not reported for one patient. Of which, one patient also received amiloride 20mg daily [routes not stated]. However, all patients developed severe hyperkalaemia [times to reactions onsets not stated]. Hence, all four patients were hospitalised.Therefore, the dosage of spironolactone was decreased to 50mg daily in one patient and 25mg daily in another patient. The patient, who had a reduction of spironolactone dosage to 25mg daily developed renal failure. Hence, treatment with spironolactone was stopped for the same patient. Treatment with amiloride was stopped in one patient [outcomes not stated].