Effect of a spirolactone on plasma and urinary aldosterone in primary aldosteronism

In primary aldosteronism due to an adrenal adenoma (n=2), treatment with a spirolactone (160 mg Canrenone/day for 7 days) decreased plasma aldosterone and urinary aldosterone-18-glucuronide. However, in the presence of a normalization in urinary aldosterone 18-glucuronide plasma aldosterone remained elevated above normal. Continued therapy with higher doses (320 mg/day for 7 days and 480 mg/day for 28 days) did not significantly alter plasma aldosterone, while urinary aldosterone-18-glucuronide returned to values comparable to those obtained before therapy. Cessation of the drug resulted in a marked increase in plasma aldosterone and urinary aldosterone-18-glucuronide. The results indicate that in primary aldosteronism due to an adrenal adenoma, the spirolactone (Canrenone) inhibits aldosterone biosynthesis and seems to influence aldosterone degradation.