In Vitro and in vivo Availability of Spironolactone from Various Oral Preparations

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Abstract
The dissolution rates in vitro and the bioavailability in humans were determined for 6 preparations containing 25 mg spironolactone and 5 preparations containing 100 mg spironolactone. Linear relationships were obtained by pairwise correlation of in vitro parameters with in vivo parameters. The following parameters were used. In vitro parameters of dissolution: 1. The area under the dissolution-time-curve up to 1 h 2. The fraction of active ingredient dissolved within 20 min. 3. The slope of the dissolution-time-curve at 50 % dissolution 4. The dissolution rate constant 5. The time up to 50 % dissolution of the substance 6. The maximum slope of the dissolution-time-curve In vivo parameters of bioavailability: 1. The time of maximum plasmaconcentration 2. The area under the plasmaconcentration-time-curve up to 1 h and 2 h after application 3. The quantities of active ingredient excreted in the urine up to 2 h after application The highest correlation coefficient was found between the areas beneath the dissolution-time-curve and the plasmaconcentration-time-curve up to 1 h each. No significant correlations were found between the within 1 h dissolved substance and maximum plasma-concentration, the area under the plasmaconcentration-time-curve up to 4 h and 24 h and quantities of active ingredient excreted in the urine up to 4 h after application.