Bioavailability of propylthiouracil in humans

Single lots of five commercially available 50-mg propyl-thiouracil formulations were evaluated in vitro and in vivo. Each product met the USP XIX specifications for drug content, content uniformity, and disintegration time. However, major differences were noted among products in their rate and extent of dissolution. Statistically significant differences (p less than 0.05) were observed in vivo among the drug formulations at all but one of the sampling times, as determined from crossover blood level studies in 12 healthy male volunteers. The differences among the areas under the plasma level-time curves for the various products were not statistically significant. No statistically significant correlations were found between the in vitro and in vivo parameters studied.