Opposite effects of spironolactone and amiloride on potassium excretion in a patient with ascites due to liver cirrhosis.

Potassium excretion was enhanced by spironolactone and it was inhibited by amiloride in a patient with ascites. One drug's effect was counteracted by the other when they were used in combination. Individual variation in the sites of action of antikaluretic drugs might be a possible explanation for the unpredictable changes in potassium excretion induced by these agents.