Efficacy of Naltrexone Hydrochloride for Preventing Relapse Among Opiate-dependent Patients After Detoxification

Abstract Objective: To investigate the efficacy of naltrexone in preventing relapse of heroin addiction among Chinese patients after successful detoxification. Methods: 302 heroin addicts were enrolled in a double-blind and an open trial conducted in 7 treatment centres for 6 months. Naltrexone 50 mg/day was given to the patients in the double-blind study and the dose was titrated from 10 to 50 mg/day in the open trial, based on the patients' responses. Results: In the double-blind study, 28.57% of naltrexone-treated patients completed the 6-month treatment course, while 7.14% of the group receiving placebo remained abstinent. In the open trial, the abstinence rate at 6 months was 23.6% and the average length of naltrexone treatment was 3.16 months compared with a previous abstinence rate of 1.2% and drug-free period of 0.5 months The non-euphoric effects reported in the naltrexone and placebo groups were 68.18% and 33.3%, respectively. The rate of positive morphine urine tests was 24.38% for the naltrexone-treated group and 40.48% for the placebo recipients. The blocking effect of naltrexone 50 mg/day was more efficient than the medium and low doses given in the open trial. Conclusion: The results of this study suggest that naltrexone is an effective medication for the prevention of relapse for heroin-dependent patients, with only mild side effects. Key words: Naltrexone, Heroin, Drug dependence, Prevention of relapse Introduction Many narcotic-dependent individuals who detoxify from heroin addiction relapse due to various psychological or environmental precipitating factors. In animal experiments, it is assumed that the euphoric effects of opiates act as a positive reinforcement of the addiction. However, if a narcotic antagonist is given, no euphoria will be experienced after opiate administration. Hence, minimisation of reinforcement via systematic opiate antagonist medication should result in the extinction of heroin craving and self-administration in experimental or psychological models. (1-3) Naltrexone hydrochloride, a competitive long-acting opiate receptor antagonist, has been used for the prevention of relapse of heroin dependence. By blocking the access of the agonist to the opiate receptor sites, naltrexone blocks analgesia, euphoria, and other physiological changes. Furthermore, naltrexone plays a role in the prevention of opium addiction relapse. (4-5) Naltrexone is now used internationally as an adjunctive medication for relapse prevention in opiate addiction. The abstinence rate for 6 months is approximately 25 to 30%, and is higher in some reports in which psychological and social support were available. (5-9) The present study was performed to assess the efficacy of naltrexone in the prevention of relapse of opiate-dependence by maintaining abstinence from opiates after detoxification. The adverse effects of naltrexone and correct dosage for Chinese addicts were also assessed. The study was conducted in 7 treatment centres in China and included double-blind and open trials. The number of patients involved was 302 and the study period lasted for 6 months. Methods Patients Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV criteria of opioid dependence. The age range was 16 to 45 years. All patients had a history of relapse, but none had severe physical or mental disease, and the results of laboratory examinations such as X-rays, electrocardiography, and liver function tests were normal. Patients had successfully completed detoxification without using opiates for at least 7 to 10 days and the results of the urine test for morphine were negative. Patients had to have a strong desire to abstain from opiates and volunteered to accept naltrexone treatment. The patients' relatives and/ or friends (sponsors) understood the treatment and guaranteed to supervise the patient's treatment. …