BACKGROUND: The currently available ldegrees Cal anesthetics have limitations in action duration. The duration ranges from 3 to 8 hours. Long acting anesthetic agents are particularly desirable to manage postoperative pain, relieve severe pain assdegrees Ciated with terminal cancer, and for nerve bldegrees Cks carried out in pain clinics. In this paper mixture of ldegrees Cal anesthetics was formulated into cylindrical pellet using biodegradable polymer and its efficacy and safety was evaluated. METHODS: Pellets were prepared by modified melting prdegrees Cess with biodegradable polyester 30 wt%, bupivacaine 35 wt%, liddegrees Caine 35 wt% and dexamethasone 0.05 wt% of polymer and drug. In vitro release kinetics of ldegrees Cal anesthetics from pellet were determined in PBS at pH 7.4, 37degrees C, and the released ldegrees Cal anesthetics were analyzed by HPLC. Nine male Sprague Dawley weighing 300~350 gm were implanted with pellets along the sciatic nerve and the sensory bldegrees Ckade was assessed by an analgesiometer. The duration data were analyzed by paired t-test using SAS 6.11. RESULTS: Ldegrees Cal anesthetics were released in a controlled manner in vitro. In general, 40~50% of the drug released for the first day, and thereafter approximately 5% released daily. Sensory bldegrees Ckade lasted to beyond 2 days at the dose of 7 mg/100 g bupivacaine and liddegrees Caine respectively. All of the animals exhibited no systemic toxicity and complete recovery. CONCLUSIONS: The results indicated that the mixture pellet demonstrated efficient and safe in prolongation of sensory bldegrees Ckade for significant period of time. The mechanisms underlying the mixture effect are under investigation.