Effect of micronization on the bioavailability and pharmacologic activity of spironolactone.

The bioavailability and pharmacologic activity of tablets containing micronized spironolactone chemical (median particle size 2.21 micrometers) were compared to those of tablets made from standard spironolactone chemical (median particle size 78.8 micrometers) in healthy men. Apart from particle size, all features of these tablets were identical. After 200-mg single doses, the bioavailability of micronized tablets was significantly higher than that of standard tablets. Furthermore, as assessed by 24-hour urine log10 10 Na/K ratio, the pharmacologic activity of micronized spironolactone was significantly greater than that of the standard formulation. The significant influence on renal antimineralocorticoid activity of raised plasma and urinary levels of canrenone, quantitatively the major active metabolite of spironolactone in man, emphasizes the clinical importance of the bioavailability of spironolactone preparations. Since this study, the process used in the manufacture of spironolactone (Aldactone) tablets has been under review.