The impact of naloxone/lofexidine combination treatment on the opiate withdrawal syndrome

Clinical studies in opiate-dependent patients suggest that detoxification treatment with opiate antagonists may accelerate the resolution of the opiate withdrawal syndrome, permitting early induction onto naltrexone maintenance treatment. The present open study compared the clinical efficacy of daily naloxone injections in conjunction with lofexidine, with conventional lofexidine monotherapy, in 49 polysubstance-misusing opiate-dependent patients. Overall, the addition of naloxone did not confer substantial benefit over lofexidine monotherapy, although area-under-the-curve analysis showed that withdrawal severity in the naloxone/lofexidine combination group was significantly less than in the lofexidine monotherapy group, who experienced more severe withdrawal symptoms on days 4, 7, 9 and 13 of treatment. There were no significant differences in rates of completion of detoxification. Blood pressure remained within normal limits in both groups. Naltrexone maintenance treatment acceptability was low; only four patients continued with treatment for 5 or more days. The modest benefit of adding naloxone to lofexidine compared to the findings of previous opiate antagonist detoxification treatment studies is discussed in the context of the hypothesis that a critical level of opiate receptor occupancy is required to accelerate resolution of opiate withdrawal; the neurochemical mechanisms which may promote this are discussed.