Release of hydrophilic drug from biodegradable polymer blends

This paper reports on the release behavior of the drug lidocaine-HCl from a immiscible polymeric blend. Biodegradable polymer blends of poly(L-lactic acid)/poly(lactic-co-glycolic acid) (PLLA/PLGA) were loaded with lidocaine-HCl, and the release of lidocaine-HCl from these blends was monitored. It was found that the release profiles were significantly affected by the affinity and subsequent partitioning of the drug into one of the two phases in the blends. It was hypothesized that the hydrophilic lidocaine-HCl seems to have a tendency to reside in the PLGA component of the PLLA/PLGA blend. This resulted in a release very much controlled by the degradation of PLGA, even when PLLA is the major phase of the blend. A mathematical model was further employed to quantify the partitioning, as well as model the lidocaine-HCl release profiles of different blend compositions.