High-dose methadone produces superior opioid blockade and comparable withdrawal suppression to lower doses in opioid-dependent humans.
BACKGROUND
The efficacy of methadone for treating heroin dependence derives, in part, from suppression of opiate withdrawal and attenuation of the effects of heroin.


OBJECTIVE
The purpose of this double-blind, within-subject, inpatient study was to determine whether larger doses of methadone, which are more effective in the treatment of opioid dependence, produce greater or longer-lasting blockade of the effects of heroin in addition to adequate withdrawal suppression.


METHODS
Participants were maintained on 30, 60, and 120 mg methadone (ascending order) for approximately 3 weeks at each dose. During each maintenance period, heroin challenges were administered at 4, 28, and 52 h after the last methadone dose. Opioid agonist effects and opioid withdrawal symptoms were assessed prior to heroin challenge. Challenge sessions consisted of three doses of heroin (0, 10, and 20 mg/70 kg; ascending order) 45 min apart.


RESULTS
All three methadone maintenance doses produced similar agonist effects. Participants tested 4 h after receiving 120 mg methadone showed complete suppression of withdrawal symptoms and full attenuation of the effects of heroin. Thirty and 60 mg methadone suppressed withdrawal for up to 52 h, but failed to block completely the effects of heroin. The effects of heroin increased slightly at longer post-methadone intervals.


CONCLUSIONS
Heroin use may persist during methadone treatment because low to moderate doses of methadone suppress withdrawal, but fail to eliminate the effects of heroin. These results provide a mechanism for the clinical observation that higher methadone doses are more effective at reducing heroin use.
Donny
Eric C
EC
Behavioral Pharmacology Research Unit, Department of Psychiatry, Johns Hopkins School of Medicine, 5510 Nathan Shock Drive, Baltimore, MD 21224, USA. edonny@jhmi.edu
Walsh
Sharon L
SL
Bigelow
George E
GE
Eissenberg
Thomas
T
Stitzer
Maxine L
ML
D000328:Adult; D000701:Analgesics, Opioid / Q000008:administration & dosage*; D000704:Analysis of Variance; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D003932:Heroin / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008691:Methadone / Q000008:administration & dosage*; D009293:Opioid-Related Disorders / Q000188:drug therapy* / Q000523:psychology; D013375:Substance Withdrawal Syndrome / Q000188:drug therapy* / Q000503:physiopathology / Q000523:psychology
D000701:Analgesics, Opioid; D003932:Heroin; D008691:Methadone