Hyperkalemia is a complications of the use of angiotensin converting enzyme inhibitors, angiotensin receptor antagonists and aldosterone antagonists. These drugs are commonly used for the treatment of hypertension and cardiac failure. We report a 84 year-old female treated with losartan 50 mg/day and spironolactone 25 mg/day that presented with a hyperkalemia of 8.4 mEq/l and bradicardia, drowsiness and respiratory depression. She required hemodialysis and ventilatory assistance. She was discharged in good conditions five days after admission.