Transdermal Delivery of Praziquantel: Effects of Solvents on Permeation Across Rabbit Skin

Abstract

To explore a new method for the transdermal delivery of praziquantel (PZQ), the effects of solvents on permeation across rabbit skin were investigated. 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. The determination of the n-octanol/water partition coefficient of PZQ in the five different solutions and assay of serum concentration following PZQ transdermal administration in rabbits were performed using HPLC. The results indicated that the transdermal absorption of the drug was related to the partition coefficient and lipophilic characteristics of the solvent. The optimal solvent for PZQ transdermal delivery was EGPE in our protocol. The solubility of PZQ in EGPE is >400 mg/ml, and the apparent partition coefficient of PZQ in the solution is 0.895 (log P value). After transdermal administration of PZQ in EGPE solution, the bioavailability is 2.85-fold that after oral administration. The serum drug concentration was maintained at 4.0 mug/ml over 4 h, which is sufficient for the treatment of schistosomiasis. At the same time, no apparent side effects were found on the skin. EGPE may thus be a promising vehicle for the transdermal delivery of PZQ in the future.