Pharmacokinetic correlates of the effects of a heroin vaccine on heroin self-administration in rats

PLoS One. 2014 Dec 23;9(12):e115696. doi: 10.1371/journal.pone.0115696. eCollection 2014.


The purpose of this study was to evaluate the effects of a morphine-conjugate vaccine (M-KLH) on the acquisition, maintenance, and reinstatement of heroin self-administration (HSA) in rats, and on heroin and metabolite distribution during heroin administration that approximated the self-administered dosing rate. Vaccination with M-KLH blocked heroin-primed reinstatement of heroin responding. Vaccination also decreased HSA at low heroin unit doses but produced a compensatory increase in heroin self-administration at high unit doses. Vaccination shifted the heroin dose-response curve to the right, indicating reduced heroin potency, and behavioral economic demand curve analysis further confirmed this effect. In a separate experiment heroin was administered at rates simulating heroin exposure during HSA. Heroin and its active metabolites, 6-acetylmorphine (6-AM) and morphine, were retained in plasma and metabolite concentrations were reduced in brain in vaccinated rats compared to controls. Reductions in 6-AM concentrations in brain after vaccination were consistent with the changes in HSA rates accompanying vaccination. These data provide evidence that 6-AM is the principal mediator of heroin reinforcement, and the principal target of the M-KLH vaccine, in this model. While heroin vaccines may have potential as therapies for heroin addiction, high antibody to drug ratios appear to be important for obtaining maximal efficacy.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain / metabolism
  • Heroin / blood
  • Heroin / metabolism
  • Heroin Dependence / metabolism
  • Heroin Dependence / prevention & control*
  • Male
  • Morphine / blood
  • Morphine / pharmacokinetics
  • Morphine / therapeutic use*
  • Morphine Derivatives / blood
  • Morphine Derivatives / metabolism
  • Rats
  • Self Administration
  • Vaccines, Conjugate / analysis
  • Vaccines, Conjugate / blood
  • Vaccines, Conjugate / therapeutic use*


  • Morphine Derivatives
  • Vaccines, Conjugate
  • Heroin
  • Morphine
  • 6-O-monoacetylmorphine