Prospects, problems, side effects, and safety of narcotic antagonists

Sustained-release naltrexone for opioid dependence

BACKGROUND

Naltrexone is an opioid antagonist which effectively blocks heroin effects. Since opioid dependence treatment with naltrexone tablets suffers from high dropout rates, several depot injections and implants are under investigation. Sustained-release formulations are claimed to be effective, but a systematic review of the literature is lacking.

OBJECTIVES

To evaluate the effectiveness of sustained-release naltrexone for opioid dependence and its adverse effects in different study populations.

SEARCH STRATEGY

The following databases were searched from their inception to November 2007: Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL, LILACS, PsycINFO, ISI Web of Science, trial database at http://clinicaltrials.gov, available NIDA monographs, CPDD and AAAP conference proceedings. The reference lists of identified studies, published reviews and relevant web sides were searched manually. Study authors and drug companies were contacted to obtain any unpublished material or missing data.

SELECTION CRITERIA

To evaluate effectiveness only RCTs were included. To evaluate safety, any clinical trial reporting adverse effects was assessed. Treatment condition was extended to include alcohol dependent subjects and healthy volunteers.

DATA COLLECTION AND ANALYSIS

Reviewers independently evaluated the reports, rated methodological quality and extracted data. Analyses were performed separately for opioid dependent, alcohol dependent and healthy participants.

MAIN RESULTS

Foe effectiveness, one report met inclusion criteria. Two dosages of naltrexone depot injections (192 and 384 mg) were compared to placebo. High-dose significantly increased days in treatment compared to placebo (WMD 21.00, 95% CI 10.68 to 31.32, p<0.0001). High-dose compared to low-dose significantly increased days in treatment (WMD 12.00, 95% CI 1.69 to 22.31, p=0.02). Number of patients retained in treatment did not show significant differences between groups. For adverse effects, seventeen reports met inclusion criteria analyses, six were RCTs. Side effects were significantly more frequent in naltrexone depot groups compared to placebo. In alcohol dependent samples only, adverse effects appeared to be significantly more frequent in the low-dose naltrexone depot groups compared to placebo (RR 1.18, 95% CI 1.02 to 1.36, p=0.02). In the opioid dependent sample, group differences were not statistically significant. Reports on systematic assessment of side effects and adverse events were scarce.

AUTHORS' CONCLUSIONS

There is insufficient evidence to evaluate the effectiveness of sustained-release naltrexone for treatment of opioid dependence. For naltrexone injections, administration site-related adverse effects appear to be frequent, but of moderate intensity and time limited. For a harm-benefit evaluation of naltrexone implants, more data on side effects and adverse events are needed.

Ultrarapid opioid detoxification: effects on cardiopulmonary physiology, stress hormones and clinical outcomes

This study explored the acute and long-term consequences of ultrarapid opioid detoxification (URD) in individuals with opioid dependence. In an open case series, seven patients underwent URD and subsequent treatment with daily naltrexone. Structured interviews, integrated rehabilitation and hair sampling were employed in the 12-week course of longitudinal follow-up. Cardiac and pulmonary physiology did not change significantly during the anesthesia phase of URD, but plasma ACTH and cortisol levels increased 15- and 13-fold, respectively. Marked withdrawal and tachypnea in all patients and respiratory distress in one patient occurred during the acute post-anesthesia phase. Withdrawal scores were significantly elevated for 3 weeks compared with baseline in the face of minimal self-reported craving for opioids. Anxiety, depression and vegetative symptoms improved gradually. Four patients remained abstinent of opioid use, two reported a brief period of opioid intake and one relapsed into daily opioid consumption. Given its effect on breathing and stress hormones, this procedure should be conducted by experienced anesthesiologists. The fact that URD and subsequent naltrexone treatment appears to cause a dissociation effect in the usual relationship between withdrawal and craving has implications for behavioral pharmacology. Further research is needed on the efficacy, safety, mechanisms and neurobiological sequelae of the procedure.