PROLONGED REGIONAL NERVE BLOCKADE BY CONTROLLED-RELEASE OF LOCAL-ANESTHETIC FROM A BIODEGRADABLE POLYMER MATRIX

Background. Prolonged nerve blockade is potentially useful in the mana gement of many acute and chronic pain problems. Aside from infusions v ia an indwelling catheter, most currently available nondestructive tec hniques for prolonging local anesthetic action cannot provide more tha n 1-2 days of blockade. Bioerodible polymer matrixes have been used to deliver a variety of drugs in patients and animals for periods lastin g weeks to years. Previously, dibucaine and bupivacaine were incorpora ted into copolymers of 1,3 bis(p-carboxy-phenoxy) propane-sebacic acid anhydride (1:4), and demonstrated sustained release in vitro followin g incubation of the drug-polymer matrixes in phosphate-buffered soluti on (pH 7.4, 37-degrees-C). Methods: In the present study, cylindrical pellets made from polymer matrixes incorporated with bupivacaine-HCI w ere implanted surgically along the sciatic nerves of rats. Neural bloc k was assessed by direct observation of motor skills and by leg-withdr awal latency to a hot surface. Biochemical and histologic examinations were performed 2 weeks after implantation. Results. Sensory and motor blockade was produced for periods ranging from 2 to 6 days. Contralat eral control legs receiving polymer implants without drug showed no bl ock. Blockade was reversible, and animals appeared to recover sensory and motor function normally. Biochemical indexes of nerve and muscle f unction were indistinguishable from contralateral controls. Conclusion s: This biodegradable polymer system provides a promising new alternat ive for the delivery of local anesthetics to peripheral nerves to prod uce prolonged blockade for the management of acute and chronic pain.