Disposition of 13-cis-retinoic acid and N-(2-hydroxyethyl)retinamide in mice after oral doses.

The concentrations of 13-cis-retinoic acid and N-(2-hydroxyethyl)retinamide in serum and tissues from mice were measured after oral dosing with 10 mg/kg. Serum levels of the drugs reached their maxima within 15-30 min and then declined in an exponential fashion with t1/2 values of 19 min and 2.9 hr, respectively. Tissue levels of 13-cis-retinoic acid reached their maxima within 15-30 min, then declined exponentially with t1/2 values of 11-19 min. Tissue levels of N-(2-hydroxyethyl)retinamide reached their maxima within 30 min to 2 hr, then declined exponentially with t1/2 values of 2.1-4.7 hr. Longer t1/2 values were observed for both 13-cis-retinoic acid and N-(2-hydroxyethyl)retinamide in the bladder (51 min and 7.3 hr, respectively). Only small amounts of the unchanged retinoids were observed in bile and feces, and none was found in urine. Polar materials, however, were present in bile, feces, and urine.