Effects of beta- and gamma-cyclodextrins on the pharmacokinetic behavior of prednisolone after intravenous and intramuscular administrations to rabbits.

The effects of beta- and gamma-cyclodextrins (CyDs) on the pharmacokinetic behavior of prednisolone after intravenous or intramuscular administration in rabbits were investigated. The serum levels of prednisolone after intravenous administration were little affected by the two CyD complexes. This might have been due to the rapid dissociation of the complexes in the large volume of body fluid. On the other hand, the serum levels of prednisolone after intramuscular administration of the CyD complexes in the form of a suspension to rabbits were significantly higher than those of the drug alone. In addition, the mean residence times of both CyD complexes were shorter than that of prednisolone alone. In contrast, there was little or no difference in pharmacokinetic parameters after intramuscular administration of the drug in the form of a solution except for Tmax between prednisolone and its CyD complexes. The enhanced rate of bioavailability of prednisolone after intramuscular administration in the form of a suspension may be due to the rapid dissolution of CyD complexes.