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.
School of Psychiatry and Clinical Neurosciences, University of Western Australia, Crawley, Western Australia.
Gary K
GK
Hulse
Hanh T T
HT
Ngo
Robert J
RJ
Tait
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