Investigation Of Dransdermal Praziquantel Delivery System And The Treatment Of Schistosomiasis Japonicum

Praziquantel（PZQ） was recommended as the first of drugs for treating schistosomiasis of mankind and animals by World Health Organization.Because it is insoluble in water and other common solents,PZQ can be only administratered orally at present,limiting its application.In order to avoid numerous problems with the oral route for PZQ,a convenient and highly effective PZQ penetrating agent will be developed.The penetrating agent can be dabed on the skin for mankind and spraied on the body for animals.This is not only convenient administration for PZQ,but also importantly significant for the enhancement of PZQ therapy effect,the implementation of simultaneous chemotherapy for mankind and animals,the blockage propagation of schistosomiasis.Because innovations in drug delivery systems can permit the development of new medicial treatments with exisdting drugs,schistosomiasis egg granuloma was treated using PZQ penetrating agent to expect finding new paths for treating this disease.The mechanism of abating egg granuloma was explored to provide new evidences of theory and practice for PZQ treating egg granuloma.Transdermal evaporation delivery system of PZQ was devised and prepared according to the chemical structure;physico-chemical characteristics of PZQ,and the mode of action of PZQ against schistosomes.The solubility of PZQ in five different solvents,ethylene glycol monophenyl ether（EGPE）,1,4-dioxane,tetrahydrofuran, dimethyl sulfoxide,and oleic acid,were measured with a UV-Vis spectrophotometer in the temperature range from 25℃to 45℃.The determination of the n-octanol/water partition coefficient of PZQ in the five different solutions were performed using UV-Vis spectrophotometer at 37℃.Serum concentration following PZQ in the five different solution transdermal administration in rabbits were measured using HPLC.Compared with oral administration,the relative bioavailability of five solutions of PZQ via the dermal route were investigated,respectively.The concentration distribution of PZQ in different tissues（heart,liver,kidney and spleen） were determined with HPLC and the pharmacokinetics of tissues was studied.Transdermal PZQ delivery system that consists of solvent（EGPE） and penetration enhancers（ethanol） was applied to worming the mice infected with Schistosoma japonicum and to treating egg granuloma of rabbits infected with Schistosoma japonicum.The main results and conclusions are as follows:1.The optimal solvent for PZQ transdermal delivery was EGPE in our protocol.The solubility of PZQ in EGPE is＞400 mg/mL,raising 3～4 times as compared with the values of documents.The apparent partition coefficient of PZQ in the solution is 0.895 （log P value）,approaching optimal condition of transdermal drug delivery.2.PZQ was desirably separated from other components in sample of serum when HPLC was applied to measuring serum concentration following PZQ transdermal administration in rabbits,remaining time 5.91min.Recovery rate of PZQ in serum sample was＞91%and relative error was＜6%during every day measurement.3.PZQ is rapidly absorbed,reaching the peak concentration(C_max) at 30 min after transdermal administration.The C_max value of PZQ in EGPE,DMSO,AO solution was 18.36μg/mL,11.74μg/mL,3.02μg/mL,and was 3.28,2.10,0.54 times compared with oral dosing,respectinely.The relative bioavailability of EGPE,DMSO,OA solution via the transdermal route relative to oral PZQ tablets was 2.85,1.89 and1.68,respectively.4.The concentration of PZQ in the liver is highest,following by the spleen,kidney and heart after transdermal PZQ delivery in mice.There were two zeniths in the concentration-time curve of PZQ in mouse liver.The first C_max was 31.78μg/mL appeared in the time of 4 min and the second C_max was 27μg/mL at the time of 15 min.5.The C_maxvalue of PZQ in serum was 35.93μg/mL at the time of 120min after the transdermal administration of evaporation delivery system that contained ethanol was 50%on the mass of mixture of solvents.The C_max was 1.96-fold compared with no ethanol system and 6.3-fold that oral administration.6.The properties of transdermal evaporation delivery system of PZQ were stabile and it convenient to preservation.There was no abnormal phenomenons from animal tested.Skin irritation and tissue necrosis were not found at transdermal administration site.7.The worm-reduction rate achieved 98.55%,100%and 100%when the transdermal delivery system of PZQ at concentration of 70μg/mL,150μg/mL and 200μg/mL were transdermallly administered,respectively,at the abdominal part of mice infected with Schistosoma japonnicum.8.New Zealand rabbits infected with Schistosoma japonnicum were transdermallly administered at dosage 200mg/kg·d×5d using transdermal evaporation delivery system of PZQ at concentration of 300mg/mL.The egg granuloma reduction rate in liver of the rabbits achieved 77%and in colon of the rabbits approached 100%.Compared with infectation control of group,the injury of liver tissue of treatment group were markedly lightened and the pathological changes of egg granuloma in liver was somewhat slowed down.9.The diffusion rate of PZQ from the epidermis to the systrmic circulation was less than that from the vehicle to the stratum corneum according to diffusion kinetics, pharmacokinetics of PZQ and the physico-chemical characteristics of solvents tesed. Hence,this type of delivery system created invisible depot of PZQ in the skin so that the transdermal delivery of PZQ can keep sustaining steady-state serum drug levels, decreasing administration frequency and increasing bioavailability of PZQ.The mechanism of reduction egg granuloma in liver of the rabbits using the system is passably that the transdermal system of PZQ can reduce first-pass metabolism effects of liver and keep high PZQ concentration in serum to kill miracidium in a maturation egg of schistosomes and to reduce a soluble egg antigen from the maturation eggs,lightening the injury of liver tissue from granuloma and slowing down the pathological changes of egg granuloma.Simultaneously,the immune function of parasitifer is passably augmented by the high PZQ concentration in serum,which leads to a reversible change of granuloma. Hence,the numbers of granuloma are markedly reduced.