title: Plasma pharmacokinetics and therapeutic efficacy of praziquantel and 4-hydroxypraziquantel in Schistosoma japonicum-infected rabbits after oral, rectal, and intramuscular administration.
abstract: The relationship between plasma level and therapeutic efficacy of praziquantel (PZQ) and its major human oxidative metabolite, 4-hydroxypraziquantel (4-OHPZQ), has been investigated in Schistosoma japonicum-infected rabbits using three different routes of PZQ administration. After intramuscular administration (20 mg/kg), the maximum level of PZQ in rabbit cardiac plasma was 1.6 +/- 1.0 micrograms/ml (mean +/- SD) 30 min after administration. After oral or rectal administration (40 mg/kg), maximum plasma levels were 0.1 +/- 0.2 microgram/ml (oral) and 0.5 +/- 0.4 micrograms/ml (rectal). The corresponding maximum 4-OHPZQ concentrations in cardiac plasma were 4.6 +/- 1.8 micrograms/ml (intramuscular), 1.7 +/- 0.5 micrograms/ml (oral), and 4.1 +/- 1.6 micrograms/ml (rectal) 2 hr after administration of PZQ. After administration of similar doses, maximum levels of PZQ in plasma from the femoral vein were 29.3 +/- 27.5 micrograms/ml (intramuscular), 0.6 +/- 1.0 microgram/ml (oral), and 0.7 +/- 0.6 microgram/ml (rectal). However, 60 min after intramuscular administration, the maximum PZQ concentration in portal venous blood was only 1.0 +/- 0.6 microgram/ml, which is substantially less than corresponding maximum portal vein levels after oral (6.8 +/- 6.5 micrograms/ml) or rectal (3.7 +/- 4.6 micrograms/ml) administration. Therapeutically, in spite of the 4-6-fold lower levels of PZQ in portal venous plasma after intramuscular administration, adult worm reduction rates in infected rabbits using the above doses were 92.2% (intramuscular), 90.1% (rectal), and 72.5% (oral), respectively, four weeks after treatment. Thus, no direct correlation between levels of PZQ in peripheral or portal venous blood and therapeutic efficacy was observed in rabbits infected with S. japonicum.
authors.affiliation: Institute of Parasitic Diseases, Chinese Academy of Preventive Medicine, Shanghai.
authors.forename: S H
authors.initials: SH
authors.lastname: Xiao
authors.forename: J Q
authors.initials: JQ
authors.lastname: You
authors.forename: H F
authors.initials: HF
authors.lastname: Guo
mesh_terms: D000284:Administration, Oral; D000285:Administration, Rectal; D000818:Animals; D007273:Injections, Intramuscular; D011223:Praziquantel / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics* / Q000627:therapeutic use; D011817:Rabbits; D012554:Schistosomiasis japonica / Q000188:drug therapy* / Q000378:metabolism
chemical_list: C067550:4-hydroxypraziquantel; D011223:Praziquantel