The implant design is a drug loaded polymer device, such as a rod, designed to control the release of a biologically active agent, such as clonidine or its derivatives, such as clonidine HCl for a prolonged period of time, such as 2 months, 3 months, 4 months, and even 4.5 months. The polymer is preferably a biodegradable polymer, such as poly(lactide-co-glycolide) or polylactic acid/polylactide. The challenge in using the HCl salt forms of drugs such as clonidine, is controlling the release of the highly water soluble drug for up to 4.5 months. It has been found that by controlling the particle size distribution of the drug powder, the drug distribution within the polymer matrix is more uniform and can be controlled. Therefore, the large aggregates, which cause rapid drug release can be eliminated.
