The in vitro liberation and the bioavailability of different brands of griseofulvin in plasma and urine in man.
The bioavailability of griseofulvin in three different brands, two microfine forms (Gricin = G, Likuden = L), and one ultramicrofine form (Gris-PEG = GP), was determined in plasma and urine in six healthy volunteers in a crossover study and compared with in vitro liberation data. GP shows a higher AUCo infinity (140 +/- 24 mumol . h . l-1) and Cmax (4.5 +/- 0.1 mumol . h-1) than the microsize brands of griseofulvin (AUCo infinity:58 +/- 7, and 45 +/- 6 mumol . h . l-1; Cmax:1.7 +/- 0.2, and 1.5 +/- 0.2 mumol . l-1; G and L, resp.), but the same tmax at the third hour. There results correspond with the in vitro liberation data. Contradictory results of the bioavailability are found by determining the amount of 6-Demethylgriseofulvin eliminated in urine. The elimination of this main metabolite after dosing with L is lower (0.18 +/- 0.02 mmol) than those of the other two brands, which do not differ (0.31 +/- 0.04; 0.32 +/- 0.02 mmol, G and GP, resp.). It is concluded that the determination of bioavailability only by means of the eliminated amount of a metabolite in urine may produce false results.
D000328:Adult; D001682:Biological Availability; D004304:Dosage Forms; D006118:Griseofulvin / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000378:metabolism* / Q000652:urine; D006801:Humans; D008297:Male; D010316:Particle Size
D004304:Dosage Forms; C024017:6-demethylgriseofulvin; D006118:Griseofulvin