Preparation of a reservoir type levonorgestrel delivery system using high molecular weight poly L-lactide

Implantable contraceptive is likely to be a promising new option for fertility control, as we have entered the twenty-first century and the world’s population grows by one billion people in a single decade. The main objective of this study was to develop a subdermal implant for levonorgestrol (a synthetic progestin from 19-norandrostanes) using a high molecular weight biodegradable polymer , i.e. poly L-lactide (PLA), to combine the advantages of both biodegradable systems (i.e. no need to surgery for the removal of the system after the drug delivery period) and non-biodegradable reservoirs (zero order release kinetics). The implants were fabricated using a simple dip casting method. Results demonstrated that the drug release profile could be completely controlled by factors such as implant body weight, presence or absence of polyethylene glycol (PEG) in the formulation, the molecular weight of the added PEGs and their amounts, presence of osmotically active agents inside the implant , and finally the amount of loaded levonorgestrel. A constant release of levonorgestrel for at least 9 months was achieved.