Poly(lactic acid) [PLA] and its co-polymers with glycolic acid [PLCG] have been known to be biodegradable and histocompatible for the past 20 years. Their physico-chemical and biological properties have been found suitable, in many instances, for sustaining drug release in vivo for days or months. Several dosage forms for parenteral administration have been investigated using these polymers and a microencapsulation technique is chosen frequently for its unique properties. There are a limited number of published papers concerning preparation and characterization of PLA or PLCG microcapsules, possibly because of commercial unavailability and difficulties in the synthesis of reproducible batches of these polymers. However, microcapsules can be made using different traditional and non-traditional techniques containing core materials ranging from biological proteins to synthetic drugs. An attempt is made here to review problems associated with the different microencapsulation techniques using PLA or PLCG. In vivo and in vitro drug release from these microcapsules is also reviewed.

Microcapsules were prepared using a poly (L-lactic acid) (L = PLA), mol. wt. 43,200, by an emulsification and solvent evaporation technique. Phenobarbitone (PB) was used as a reference drug, (core to polymer ratio, 1:1). Both the o/w and w/o emulsion system were investigated in order to study microcapsule properties affected by the preparative technique. In the o/w system, dichloromethane (DCM) was used to dissolve L = PLA and PB and the resulting solution was dispersed in 1 per cent aqueous gelatin solution. Subsequent evaporation of the DCM resulted in the formation of microcapsules. PB was found to be poorly encapsulated within microcapsules from this o/w system. PB content in the microcapsules was found to improve using PB saturated aqueous gelatin solution as the continuum. In the w/o system, acetonitrile (AN) was used as a solvent for L-PLA and PB and light liquid paraffin (LLP), containing 2 per cent w/w Span 40, as the continuous phase. PB loading in the microcapsules was found to be very high from this w/o system. Microcapsules from the o/w system were very small compared to microcapsules obtained from the w/o system. The morphology of the microcapsules and the surface properties were found to be affected distinctly by the two techniques. Microcapsules from the o/w system showed a smooth and less porous surface, whereas a highly porous surface containing embedded PB crystals was found in the microcapsules from the w/o system.