title: Liposomal prilocaine: preparation, characterization, and in vivo evaluation.
abstract: OBJECTIVE
  This study reports the development and in vivo evaluation of a liposomal system for the local anesthetic, prilocaine.
  
  
  METHODS
  Liposomal prilocaine was prepared with egg phosphatidylcholine, cholesterol and a-tocopherol (4:3:0.07 molar ratio). The size of the liposomes was measured by laser light scattering and the effect of prilocaine on membrane fluidity made use of electron spin resonance (ESR). The anesthetic effect of liposomal prilocaine was compared to that of plain prilocaine solution (with or without vasoconstrictor) in a rat infraorbital nerve blockade model.
  
  
  RESULTS
  Laser light-scattering analysis showed one major vesicle population of liposomes with ca 400 nm (100%), without size changes after prilocaine incorporation. The ESR results showed a decrease in the orientation of the phospholipid molecules into the liposomes (ca 11%) in the presence of prilocaine, which characterized the prilocaine-liposome interaction. A prolongation of anesthetic effect was produced by liposomal prilocaine in comparison to plain prilocaine (without vasoconstrictor, p<0.001). However, no statistical differences were found after comparison between liposomal prilocaine and vasoconstrictor-containing prilocaine.
  
  
  CONCLUSIONS
  We suggest that the encapsulation of prilocaine in liposomes facilitates the controlled release of prilocaine (increasing the time of duration of the sensory nervous blockade) and constitutes a good choice to replace vasoconstrictor-containing local anesthetic formulations.
authors.affiliation: Departamento de Bioquímica, Instituto de Biologia, Universidade Estadual de Campinas, UNICAMP, Campinas, SP, Brazil.
authors.forename: Cíntia Maria Saia
authors.initials: CM
authors.lastname: Cereda
authors.forename: Daniele Ribeiro
authors.initials: DR
authors.lastname: de Araujo
authors.forename: Giovana Bruschini
authors.initials: GB
authors.lastname: Brunetto
authors.forename: Eneida
authors.initials: E
authors.lastname: De Paula
mesh_terms: D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000494:pharmacology; D000818:Animals; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004339:Drug Compounding; D008081:Liposomes / Q000138:chemical synthesis; D008297:Male; D010316:Particle Size; D011318:Prilocaine / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000779:Anesthetics, Local; D008081:Liposomes; D011318:Prilocaine