Preparation of biodegradable levonorgestrel rods.

This article describe the preparation and manufacture as well as the implantation and removal of biodegradable levonorgestrel rods. After extensive in vivo studies of levonorgestrel release from poly (lactic/glycolic acid) polymers of differing composition ratios molecular weights and drug loading formulation of a system calling for release of 50-100 mcg of levonorgestrel/day for 12 months has been possible. The manufacture of these rods occurs in 2 stages: 1st the drug-polymer matrix is formed and 2nd there is compression of the matrix and formulation of the rods by extrusion. The matrix is formed by casting a solution of polymer and drug onto a glass plate then rapidly removing the solvent by evaporation. A film is peeled from the glass plate and vacuum dessicated. A hydraulic press is used for rod extrusion. To be acceptable rods must have smooth straight sides with no pits or cracks. Although the rods have a slight plasticity they will break under strenuous manipulation. Once the tip of a rod is exposed it can be pulled out easily without breakage.