Progressive hypokalaemia in elderly patients taking three thiazide potassium-sparing diuretic combinations for thirty-six months.

Three different thiazide potassium-sparing diuretic combinations were given to elderly patients for heart failure. Eighty patients received their allocated combinations for 3 years and had 6-monthly measurements of plasma potassium. A further 84 were recruited for study but 29 died within 6 months and 55 had to be withdrawn from the trial. The triamterene-containing preparation was discontinued most frequently (6/44) because of hypokalaemia (plasma potassium less than 3.0 mmol/l); amiloride (5/44) and spironolactone (1/47). The median fall in plasma potassium over 3 years in those patients not withdrawn because of hypokalaemia was similar in each case (P greater than 0.05) and possibly failed to reach significance because of the withdrawal rate (9%). The trend was for a greater fall in those patients taking triamterene. The spironolactone-containing preparation may be the least unsatisfactory of the three.