Risk factors for craving and relapse in heroin users treated with oral or implant naltrexone.
BACKGROUND
Oral naltrexone effectively antagonizes heroin, but patient noncompliance limits its utility; sustained-release preparations may overcome this. Few data are available on optimal blood naltrexone levels for preventing craving and/or return to heroin use. This study assesses various risk factors, including blood naltrexone level, for heroin craving and relapse to illicit opioids.


METHODS
Heroin-dependent persons from a randomized controlled trial of oral versus implant naltrexone were followed up for 6 months. Thirty-four participants received 50 mg oral naltrexone daily, plus placebo implant; thirty-five participants received a single dose of 2.3 g naltrexone implant, plus daily oral placebo tablets.


RESULTS
Compared to oral naltrexone patients, implant naltrexone patients were significantly less likely to use any opioids and had one-fifth the risk of using heroin > or = weekly. Risk of > or = weekly heroin use increased by 2.5 times at blood naltrexone concentration < .5 ng/mL compared with > or = .5 ng/mL, with 3 ng/mL associated with very low risk of use. Craving remained near "floor" levels for implant patients but rebounded to higher levels among oral patients. Lower craving scores (< or = 20/70) predicted lower relapse risk. Noncompliance with daily oral formula, higher baseline craving, longer history of use, and being younger predicted higher craving at follow-up.


CONCLUSIONS
Implant naltrexone was better associated with reduced heroin craving and relapse than oral naltrexone. Effective treatment was achieved at blood naltrexone levels of 1 ng/mL to 3 ng/mL, with higher levels associated with greater efficacy. Craving assessment may be valuable in predicting relapse risk allowing timely intervention.
Hulse
Gary K
GK
School of Psychiatry and Clinical Neurosciences, University of Western Australia, Crawley, Western Australia.
Ngo
Hanh T T
HT
Tait
Robert J
RJ
D000328:Adult; D003692:Delayed-Action Preparations; D004311:Double-Blind Method; D004343:Drug Implants; D058999:Drug-Seeking Behavior / Q000187:drug effects*; D005260:Female; D005500:Follow-Up Studies; D006556:Heroin Dependence / Q000097:blood / Q000188:drug therapy* / Q000517:prevention & control; D006801:Humans; D008297:Male; D009271:Naltrexone / Q000008:administration & dosage* / Q000097:blood; D009292:Narcotic Antagonists / Q000008:administration & dosage* / Q000097:blood; D010349:Patient Compliance; D012008:Recurrence; D012307:Risk Factors; D013607:Tablets; D016896:Treatment Outcome
D003692:Delayed-Action Preparations; D004343:Drug Implants; D009292:Narcotic Antagonists; D013607:Tablets; D009271:Naltrexone