In-vivo evaluation in man of a hydrophilic matrix containing propylthiouracil

To reduce the number of administrations of propylthiouracil required to treat hyperthyroidism, the bioavailability and sustained-release characteristics of 300 mg propylthiouracil formulated in hydrophilic matrix tablets were evaluated after single oral administration in healthy male volunteers. A conventional tablet was chosen as the reference formulation. For tablets formulated from three different types of hydroxypropylmethylcellulose, K15M, K4M and K100LV, propylthiouracil dissolution in-vitro was 40%, 51% and 100%, respectively, in 8 h. The three matrix formulations showed sustained plasma concentration-time profiles. The relative bioavailability was 50, 51 and 87%, respectively, for K4M, K15M and K100LV hydroxypropylmethylcellulose matrix tablets. When reverse triiodothyronine concentrations were plotted against the corresponding propylthiouracil concentrations, an antihysteresis loop was observed with the conventional tablets and the K100LV matrix tablet. A linear concentration-response curve was obtained for both the K4M and K15M formulations. The results showed that the K100LV matrix tablet gave a sustained plasma concentration-time profile and a bioavailability and extrathyroidal effect similar to that of a conventional tablet.