Bioavailability of terfenadine in man.

Fourteen normal male subjects were given either 60mg or 180mg of terfenadine suspension in a randomized two-way crossover study. Peak plasma concentrations of 1.544 +/- 0.726 (mean +/- S.D.) ng ml-1 were obtained in 0.786 h following the 60 mg dose and displayed an AUC or 11.864 +/- 3.369 ng h ml-1. Whereas peak plasma concentrations of 4.519 +/- 2.002 ng ml-1 in 1.071 +/- 0.514 h were obtained following the 180 mg dose. The AUC following the 180 mg dose was 44.341 +/- 22.041 ng h ml-1. When 60 mg of 14C terfenadine was given to six additional subjects, the peak plasma concentrations of 351 +/- 43 ng equivalents per ml were obtained in 1.67 +/- 0.41 h and the AUC was 2297.71 +/- 310.85 ng-equivalents h ml-1. This indicates that approximately 99.5 per cent of the terfenadine related material that is absorbed undergoes biotransformation. Urinary excretion of 14C accounted for 39.89 +/- 5.29 per cent of the dose while 60.58 +/- 2.44 per cent of the dose was recovered in the feces in twelve days. Thin-layer chromatographic (TLC) examination of fecal extracts showed only a trace of material chromatographing with terfenadine. This may indicate that the 14C present in the feces is not due to lack of absorption.

Duke Scholars

Author Chad E. Cook Orthopaedic Surgery, Physical Therapy