PROGRESS IN THE DEVELOPMENT OF ULTRA-LONG-ACTING LOCAL-ANESTHETICS

Background and Objectives. Local anesthetic agents with a duration of action longer than the currently available local anesthetics could hav e widespread clinical application for the treatment of both chronic an d acute pain. Over the last several decades, several different approac hes have been used in the development of ultra-long-acting agents. The re are currently promising preparations in development which may prove clinically useful in the near future. Methods. A Medline search was c onducted for relevant articles published in peer-reviewed journals bet ween 1971 and 1996. Investigations related to prolongation of the effe ct of local anesthetics either by alterations in the local anesthetic molecule, use of new or novel agents, or use of new delivery systems w ere reviewed. In addition, bibliographies of relevant articles were se arched to capture any articles that were missed by the Medline search. Results. Over the last several decades, numerous attempts have been m ade to prolong the duration of action of local anesthetics. Initially research focused on alterations in the local anesthetic molecule or th e identification of new agents with local anesthetic action. Recently, the focus of much of the work has shifted to new drug-delivery system s such as polymers and liposomes. Conclusions. Although encouraging re sults have been reported in the literature, there is currently no agen t or delivery system that has shown reliable and practical prolongatio n of local anesthetic effect in humans. There have been several encour aging reports in animals that have shown local anesthetic effects last ing up to several days, bur these results must be validated and then p erformed in human studies before a clinically useful agent is found. F urther research is warranted.