A Case of Heart Failure Suffered from Hyperkalemia after Combined Therapy of Spironolactone with Losartan Potassium.

A 74-year-old woman had been treated for chronic heart failure, atrial fibrillation, mitral regurgitation and tricuspid regurgitation at a local clinic since 1992. Her heart function was well controlled by adjusting the circulatory plasma volume using 25 mg/day of spironolactone and 2 mg/day of trichlormethiazide. In December 2000, however, the patient was admitted to our hospital because of aggravated heart failure. On admission, her serum potassium (K) level was 3.8 mEq/L. A combined therapy of 50 mg/day of spironolactone with 50 mg/ day of losartan potassium was started and the heart failure symptoms improved markedly, while her serum K level reached 7.0 mEq/L. Calcium polystyrene sulfonate (CPS) was thus administered in place of spironolactone. After 5 days, her serum K level decreased to 5.0 mEq/L and stabilized at around 4.6 mEq/L even after discontinuation of CPS. The patient had a normal renal function in the past and received 25 mg/day of spironolactone for 9 years without any appearance of hyperkalemia. When spironolactone at an increased dose of 50 mg/day was administered in combination with 50 mg/day of losartan potassium, her serum K level increased to 7.0 mEq/L which was subsequently normalized after the discontinuation of spironolactone. In the present case, the hyperkalemia observed in this patient seemed to have been caused by the combination therapy of spironolactone with losartan potassium.When the administration of losartan potassium is initiated in a patient receiving spironolactone for diuresis, it is considered necessary to carefully observe for any possible changes not only in BUN and Scr but also in the serum K levels. Furthermore, it is very important for clinical pharmaceutists in the future to investigate this disease from the viewpoint of their field so as to determine any drug causing adverse reactions, to select the administration drug according to the drug kinetics, and to estimate and prevent the appearance of any adverse reactions and transactions.