Comparison of potassium alone and potassium-magnesium supplementation in patients with heart failure using hydrochlorothiazide.

Supplementation of potassium alone and in combination with magnesium was compared in 10 patients with chronic compensated heart failure receiving hydrochlorothiazide 50 mg twice daily for the whole trial. After a 3-week run-in period, the patients were randomized to receive active supplementation for 6 weeks in a double-blind cross-over manner. A 3-week wash-out period was kept in between. Addition of 2 g potassium chloride daily (27 mmol K+) did not efficiently correct the serum potassium concentration. After the combined supplementation of 2 g potassium and 1 g magnesium (27 mmol K+ and 17 mmol Mg2+ daily), both serum potassium and magnesium concentrations increased statistically significantly during the first 2 weeks of treatment. After a longer treatment of 6 weeks, the effect of combined supplementation was less clear, even though a trend toward a better maintenance of serum potassium was still evident.