Comparison of systemic absorption of aqueous and liposomal lidocaine following intra-articular injection in rabbits.

Aqueous lidocaine is a local anesthetic that is frequently used in intra-articular injection. However, aqueous lidocaine may be less than ideal because of its rapid absorption. Liposomes can serve as drug carriers for encapsulating lidocaine. Both aqueous lidocaine and liposomal lidocaine were injected into knee joints of adult rabbits and the pharmacokinetic changes were studied. The peak serum level of lidocaine from the liposomal preparation was significantly lower than that from the aqueous preparation. The amount of lidocaine absorbed in 4 hours was also significantly lower in the liposomal group. This phenomenon may have been due to local accumulation of liposomal lidocaine and the slow release of lidocaine from liposomes. Intra-articular use of liposomal lidocaine may have advantages over the aqueous form because of its lower systemic serum concentration.