title: Opioid-based micro and nanoparticulate formulations: alternative approach on pain management.
abstract: BACKGROUND
  Opioids have been used as the reference treatment on chronic pain. However, they are related to serious adverse effects which affect the patient compliance to treatment, as well as, his quality of life. Particulate formulations have been investigated as an alternative to improve opioid efficacy and safety.
  
  
  OBJECTIVE
  Summarise the available studies concerning micro and nanoencapsulated opioid formulations discussing their biopharmaceutical characteristics, such as composition, size, in vitro release, pharmacokinetic and antinociceptive profile.
  
  
  METHODS
  Papers available in 1995-2015 at Medline, Science Direct and Web of Science databases were collected and assessed. Searches were performed using varied combinations of the keywords of this work.
  
  
  RESULTS
  Opioid-loaded particles showed prolonged drug release with maintenance of serum therapeutic concentrations and extended analgesia when compared with the free drugs. The side effects incidences were reduced or maintained the same.
  
  
  CONCLUSIONS
  Particulate formulations can significantly increase both potency and safety profiles of opioids.
authors.affiliation: a Programa de Pós Graduação em Engenharia Industrial, Escola Politécnica , Universidade Federal da Bahia , Salvador , Bahia , Brazil ;
authors.forename: André
authors.initials: A
authors.lastname: São Pedro
authors.affiliation: b Programa de Pós-Graduação em Farmácia, Faculdade de Farmácia , Universidade Federal da Bahia , Salvador , Bahia , Brazil ;
authors.forename: Renan
authors.initials: R
authors.lastname: Fernandes
authors.affiliation: b Programa de Pós-Graduação em Farmácia, Faculdade de Farmácia , Universidade Federal da Bahia , Salvador , Bahia , Brazil ;|c Laboratório de Imunofarmacologia e Engenharia Tecidual, Centro de Pesquisas Gonçalo Muniz - Fiocruz , Salvador , Bahia , Fiocruz , Brazil.
authors.forename: Cristiane Flora
authors.initials: CF
authors.lastname: Villarreal
authors.affiliation: a Programa de Pós Graduação em Engenharia Industrial, Escola Politécnica , Universidade Federal da Bahia , Salvador , Bahia , Brazil ;
authors.forename: Rosana
authors.initials: R
authors.lastname: Fialho
authors.affiliation: a Programa de Pós Graduação em Engenharia Industrial, Escola Politécnica , Universidade Federal da Bahia , Salvador , Bahia , Brazil ;
authors.forename: Elaine Cabral
authors.initials: EC
authors.lastname: Albuquerque
mesh_terms: D000701:Analgesics, Opioid / Q000737:chemistry / Q000627:therapeutic use; D000818:Animals; D004337:Drug Carriers / Q000737:chemistry / Q000627:therapeutic use; D006801:Humans; D053758:Nanoparticles / Q000737:chemistry*; D010146:Pain / Q000188:drug therapy*
chemical_list: D000701:Analgesics, Opioid; D004337:Drug Carriers
keywords: Opioids; liposomes; nanostructured lipid carriers; polymer particles; solid lipid nanoparticles