Effects of liquid and freeze-dried grapefruit juice on the pharmacokinetics of praziquantel and its metabolite 4 '-hydroxy praziquantel in beagle dogs

three-phase crossover study, six male beagle dogs were administered 100 ml of water (control), 100 ml of commercial liquid grapefruit juice, or 10 g of freeze-dried grapefruit juice (equivalent to 100 ml of liquid grapefruit juice) with 100 ml of water, followed after 2 h by single oral dose of praziquantel (30 mg kg−1). After treatment, the dogs were sampled at different times. Determination of praziquantel and its metabolite 4-hydroxy praziquantel (identified by GC/MS) was performed by HPLC. Liquid and freeze-dried grapefruit juice preadministration increased the Cmax of praziquantel about three-fold and the AUC 2.5- and 2.3-fold, respectively. The Tmax (0.75 h) was unaffected by liquid or freeze-dried grapefruit juice, while T1/2 was 2.3- and 1.7-fold higher compared with controls. The amount of 4-hydroxy praziquantel was also affected by both liquid and freeze-dried grapefruit juice administration: the AUC and Cmax increased four- and three-fold, respectively and the Tmax was significantly enhanced. These findings demonstrate that both freeze-dried grapefruit juice and commercial liquid grapefruit juice significantly increase plasma concentrations and T1/2 of praziquantel in dogs. © 2002 Elsevier Science Ltd. All rights reserved.