ABSTRACT
Depot delivery systems provide one way to mitigate the impact of injections by decreasing the frequency of administration. They offer the advantage of a more convenient and accessible patient therapy which can be administered at home using patient-friendly devices or in office procedures by a health care practitioner. This chapter summarizes such biodegradable depot systems and highlight the various depot delivery technologies utilizing those polymers. One of the key aspects of an implantable, nondegradable depot delivery system is the requirement for a minor surgery for implantation and a similar procedure for explanation of the implant once the dose has been delivered. Formulations based on suspensions of drug substance in aqueous or oily vehicles were among the first long-acting injectable delivery systems developed. Selection of in vitro release methods remains a significant challenge in the development of depot formulations and little in the way of science-based guidance for industry exists.
