Review of prolonged local anesthetic action.

IMPORTANCE OF THE FIELD: Pain following surgery is often treated by local anesthetic agents. Duration of the analgesia can be extended safely following administration of encapsulated large doses of local anesthetic agents. AREAS COVERED IN THIS REVIEW: This review considers formulations used for encapsulation of local anesthetic agents for prolonged anesthesia effect. All studies describing encapsulation of a commercial local anesthetic agent for providing prolonged analgesia were considered using the NCBI Medline site. of local anesthetic, prolonged anesthesia, polymers and liposomes were entered in order to retrieve appropriate articles and reviews from 1966 to 2010, with emphasis on the last 10 years. Reference pages were searched manually for other relevant articles. The topics covered include an overview of local anesthetic agents and a review of local anesthetic carrier agents, with emphasis on liposomes and polymer carriers. Articles were limited to the English language. WHAT THE READER WILL GAIN: The current research areas for prolongation of local anesthetic effect are evaluated, along with their limitations. Each topic has been summarized, and the review has attempted to cover all current laboratory and clinical studies in a simple manner that should also be useful for readers without a pharmacology background. The direction of research is promising and exciting, and this review should be a useful up-to-date reference. TAKE HOME MESSAGE: Many formulations including polymer and liposome carriers have facilitated prolonged local anesthetic action for several days, although few clinical studies have been performed. This field promises a safe way to deliver local anesthetics for effect far beyond that of commercially available agents, with potential cost and health benefits for patients suffering chronic or postoperative pain.