Spironolactone (SPL) was obtained from Sigma-Aldrich, St. Louis, MO, USA. Poly(lactic-co-glycolic acid) (PLGA) (lactide–glycolide 50:50 (ester terminated) and 75:25 (acid terminated), Viscosity 1 and 0.2 dL/g, respectively) was kindly supplied by Purac Biomaterials, Holland. Polyvinyl alcohol (87.0–89.0% hydrolyzed, molecular weight 31,000–50,000 Da) was obtained from Acros Organics, Belgium. Acetone, methylene chloride, dimethylsulfoxide (DMSO), and methanol were bought from Adwic, EL Nasr Pharmaceutical Chemicals, Co., Egypt. All other materials were of fine analytical grades. Praziquantel (PZQ) was supplied from Alexandria Company for Pharmaceuticals & Chemical Industries, Egypt.