In Vitro Evaluation of Poly-(ε-Caprolactone-Co-L-Lactide) Implants Containing Trypanocidal Drugs

Poly(e-caprolactone-co-L-lactide) copolyesters with different compositions were synthesized by bulk polymerization. The copolymers were characterized by NMR, GPC, and DSC analyses. Slow release devices were obtained as rods by extrusing polymer/drug mixtures (75/25, w/w) prepared by solution casting. The rods were coated by dipping in a methylene chloride solution of the core polymer. The in vitro release of isometamidium chloride (IMM) and ethidium bromide (EtBr), from these rods was carried out in phosphate buffer (PB) pH 7.4 at 3700. The release of IMM is faster than for EtBr. Initial IMM release is governed by osmotic pressure, whereas EtBr release is mainly diffusion controlled. The in vitro release of these drugs is governed by polymer matrix degradation at the later stage of the release process. The in vitro release of IMM from these copolymers depends on polymer composition and coating thickness. The in vitro release of EtBr may be controlled by polymer composition, polymer molecular weight, coating thickness, and device geometry.