The pharmacokinetics of fluocortolone and prednisolone after intravenous and oral administration.

The pharmacokinetics of fluocortolone and of prednisolone were examined following a single intravenous injection of 5 mg and oral administrations of 10 and 20 mg to five healthy male volunteers. After intravenous injection the plasma levels of fluocortolone decreased biexponentially with half-lives of 9 +/- 5 min and 1.3 +/- 0.3 h. Total plasma clearance of fluocortolone was calculated to be 7.0 +/- 1.5 ml/min/kg. Oral administrations of fluocortolone revealed maximum plasma levels of 86 +/- 12 ng/ml (10-mg dose) and 174 +/- 34 ng/ml (20-mg dose) after 1.4 +/- 0.2 h. Intravenously administered prednisolone was rapidly distributed (t 1/2 alpha = 5 +/- 3 min) but more slowly eliminated from plasma than fluocortolone (t1/2 beta = 3.1 +/- 0.8 h). Correspondingly a total plasma clearance of 2.2 +/- 0.2 ml/min/kg was calculated. Oral administrations revealed maximum prednisolone plasma levels of 172 +/- 25 ng/ml (10-mg dose) and 278 ng/ml (20-mg dose) after 1.6 +/- 0.7 h. The absolute bioavailability of both corticosteroids was higher than 80% and independent of both dose levels investigated.