Activity of sulfur-containing intermediate metabolites of spironolactone

The renal antimineralocorticoid activity of single administration of 2 sulfur-containing compounds, which are thought to be intermediate metabolites of spironolactone, was assessed in healthy subjects. They were each active in reversing the urinary electrolyte changes indiced by fludrocortisone for 2 to 10 hr after dosing, but only the 7 alpha-thiomethyl derivative exhibited activity in the period 12 to 16 hr after treatment. The activity of both drugs was less than of spironolactone. Taking urinary log 10 Na/K as the best index of antimineralocorticoid activity, the potencies of the intermediates relative to spironolactone were 0.26 (95% confidence limits, 0.12 to 0.49) for 7 alpha-thio-spirolactone and 0.33 (95% confidence limits, 0.15 to 0.62) for 7 alpha-thiomethyl-spirolactone in the period 2 to 10 hr after medication. We conclude that these minor sulfur-containing intermediate metabolites of spironolactone are unlikely to contribute significantly to the renal antimineralocorticoid activity of spironolactone.