Abstract: Our results show that in liver microsomes from erythromycin, acetylspiramycin and dexamethsone pretreated rats, the rate of praziquantel (PQT)disappearence was increased as compared with control rat When microsomes from erythromycin-treated rats were exposed to PQT in the presence of potassium ferricyanide which broke down the cytochrome P-450 Fe(II)-metabolite complexes and restored the functional cytochrome P-450, PQT metabolism was further increased. Acetylspiramycin did not form the complexes, so potassium ferricyanide showed no effect on the PQT metabolism in microsomes from acetylspiramycin-treated rats. Triacetyloleandomycin, a specific inhibitor of cytochrome P-450 III Al, inhibited PQT metabolism by 53% in liver microsomes from dexamethasone-treated rats.These results indicate the cytochrome P-450 III Al seems to be involved in metabolism of PQT in rat liver microsomes.

Key words: Praziquantel, Liver microsomes, Dexamethasone, Erythromycin, Cytochrome P-450, Rat