title: Alpha 1-acid glycoprotein (AAG) and serum protein binding of methadone in heroin addicts with abstinence syndrome.
abstract: OBJECTIVE
  To quantify serum protein levels and protein-binding of methadone in vitro in heroin-addicted patients showing objective signs of heroin abstinence.
  
  
  METHODS
  Serum samples were obtained from patients (n = 27) hospitalized to participate in a methadone detoxification program and from healthy volunteers (n = 21). The severity of the abstinence syndrome was assessed before blood sampling using a standardized scale. Concentrations of both albumin and alpha1-acid glycoprotein (AAG) were measured in all serum samples. The protein-binding of alpha1-methadone was determined by the ultrafiltration technique and the unbound concentration was measured by liquid scintillation counting.
  
  
  RESULTS
  The mean of the AAG concentrations was significantly increased in patients showing signs of withdrawal while the albumin concentrations did not change. Also, the unbound methadone was significantly decreased in this group when compared to the control. A positive correlation (Pearson r = 0.48; p < 0.005) indicates that AAG levels rise during abstinence as the score of withdrawal symptoms increases. Additionally, pooled data from all individuals show the binding of methadone to be related to AAG (r = 0.46; p < 0.05) levels and not to albumin.
  
  
  CONCLUSIONS
  The observed changes in protein-binding in abstinence individuals suggest the need for increased dosages of methadone when such patients are treated. Levels of AAG or protein-binding appear to be components of the interindividual variance observed in the response to methadone treatment, hence these variables could be included in future kinetic and dynamic studies.
authors.affiliation: Department of Pharmacology, School of Medicine, University of the Basque Country, Leioa, Spain.
authors.forename: M J
authors.initials: MJ
authors.lastname: Garrido
authors.forename: C
authors.initials: C
authors.lastname: Aguirre
authors.forename: I F
authors.initials: IF
authors.lastname: Trocóniz
authors.forename: M
authors.initials: M
authors.lastname: Marot
authors.forename: M
authors.initials: M
authors.lastname: Valle
authors.forename: M K
authors.initials: MK
authors.lastname: Zamacona
authors.forename: R
authors.initials: R
authors.lastname: Calvo
mesh_terms: D000328:Adult; D001798:Blood Proteins / Q000378:metabolism*; D006556:Heroin Dependence / Q000097:blood*; D006801:Humans; D008691:Methadone / Q000097:blood*; D009294:Narcotics / Q000097:blood*; D009961:Orosomucoid / Q000378:metabolism*; D011485:Protein Binding; D012044:Regression Analysis; D012720:Severity of Illness Index; D013375:Substance Withdrawal Syndrome / Q000097:blood*
chemical_list: D001798:Blood Proteins; D009294:Narcotics; D009961:Orosomucoid; D008691:Methadone