Stable Biodegradable Polymers for Delivery of Both Polar and Non-Polar Drugs

The development of a controlled release implant for pain relief of pain is described. The analgesic hydromorphone is proposed for incorporation into a biodegradable excipient designed for continuous release for one week to several weeks. The proposed relatively short duration minimizes the possibility of dependence and permits flexibility in dosing by recognizing that delivery for longer periods may not be necessary. The excipient uses a modified poly(lactide-co-flycolide), PLGA, prepared as a porous, open celled foam into which the drug is incorporated as microcrystals trapped within the cells. The foam/drug matrix is extruded under high pressure to produce a high density nonporous dose form which is then cryogenically ground and sieved to small particles suitable for injection by a conventional hypodermic needle. This method of matrix fabrication may be applied to both polar and nonpolar agents. Generally polar agents will be more soluble than nonpolar, and will release faster. Release rates may be controlled by choice of lactide:glycolide copolymer rations, polymer molecular weight, loading, and extrusion pressure.