20-Hydroxyecdysone (20-OH) is a natural compound with many demonstrated effects on the physiological functions of vertebrates, particularly increased protein synthesis. Our study sought a suitable dosage form with continuous release of the drug lasting several weeks for implantation into agricultural animals. Biodegradable microparticles and implants of poly(L-lactic) and poly(DL-lactic) acids were prepared. Oligomers of these materials were synthesized, and a method of melting the binary mixture of the oligomer and 20-OH was employed. The particles were prepared simply by grinding the solidified block of the melt and sieving. Implants were prepared by extruding the melt into silicone tubes, removing the solidified content, and cutting into cylinders of 2 mm diameter and various lengths. A new method of preparation of hollow cylinders by aspirating air into silicone tubes filled with the melt was developed. The experiments demonstrated stability of 20-OH during heat treatment. Release of the active ingredient was tested in static in vitro conditions, analogous to those at the site of implantation, and prolonged drug release was obtained with both types of implant. The hollow implants gave release rates nearest to ideal zero-order kinetics and would appear most appropriate for testing in vivo.

Department of Pharmaceutics Faculty of Pharmacy Charles University Heyrovského 1203 500 05 Hradec Králové Czech Republic

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