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Encapsulation of mepivacaine prolongs the analgesia provided by sciatic nerve blockade in mice

[La micro-encapsulation de la mépivacaïne prolonge l’analgésie fournie par le bloc du nerf sciatique chez la souris]

Daniele R. de Araujo^*, Cíntia M.S. Cereda^*, Giovana B. Brunetto^*, Luciana M.A. Pinto, PhD^*, Maria Helena A. Santana, PhD and Eneida de Paula, PhD^*

^* From the Department of Biochemistry, Institute of Biology, State University of Campinas; and
the Department of Biotechnological Process, Faculty of Chemical Engineering - UNICAMP, Campinas, Sao Paulo, Brazil.

Address correspondence to: Dr. Eneida de Paula, Departamento de Bioquímica, Instituto de Biologia, UNICAMP, C.P. 6109, CEP 13083-970, Campinas, SP, Brazil. Phone: +55 19 3788 6143; Fax: +55 19 3788 6129; E-mail: depaula{at}unicamp.br

Purpose: Liposomal formulations of local anesthetics (LA) are able to control drug-delivery in biological systems, prolonging their anesthetic effect. This study aimed to prepare, characterize and evaluate in vivo drug-delivery systems, composed of large unilamellar liposomes (LUV), for bupivacaine (BVC) and mepivacaine (MVC).

Methods: BVC and MVC hydrochloride were encapsulated into LUV (0.4 µm) composed of egg phosphatidylcholine, cholesterol and -tocopherol (4:3:0.07 molar ratio) to final concentrations of 0.125, 0.25, 0.5% for BVC and 0.5, 1, 2% for MVC. Motor function and antinociceptive effects were evaluated by sciatic nerve blockade induced by liposomal and plain formulations in mice.

Results: Liposomal formulations modified neither the intensity nor the duration of motor blockade compared to plain solutions. Concerning sensory blockade, liposomal BVC (BVC_LUV) showed no advantage relatively to the plain BVC injection while liposomal MVC (MVC_LUV) improved both the intensity (1.4–1.6 times) and the duration of sensory blockade (1.3–1.7 times) in comparison to its plain solution (P < 0.001) suggesting an increased lipid solubility, availability and controlled-release of the drug at the site of injection.

Conclusion: MVC_LUV provided a LA effect comparable to that of BVC. We propose MVC_LUV drug delivery as a potentially new therapeutic option for the treatment of acute pain since the formulation enhances the duration of sensory blockade at lower concentrations than those of plain MVC.

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				C. M. S. Cereda, G. B. Brunetto, D. R. de Araujo, and E. de Paula Liposomal formulations of prilocaine, lidocaine and mepivacaine prolong analgesic duration: [Des preparations liposomiques de prilocaine, de lidocaine et de mepivacaine prolongent la duree de l'analgesie]. Can J Anesth, November 1, 2006; 53(11): 1092 - 1097. [Abstract] [Full Text] [PDF]