Opioid detoxification using naloxone

American College of Medical Toxicology and the American Academy of Clinical Toxicology position statement: nalmefene should not replace naloxone as the primary opioid antidote at this time

BACKGROUND

Nalmefene is a potent opioid antagonist that has recently been reintroduced in the United States to treat known or suspected opioid overdose.

NALMEFENE CLINICAL TRIAL DATA

The injection formulation, which had been withdrawn in 2008, was reintroduced in 2022, and in 2023 the United States Food and Drug Administration approved a new intranasal formulation of nalmefene. Because nalmefene had been previously approved for use in 1995 via injection, the new intranasal formulation did not require new clinical data as it was approved under an Abbreviated New Drug Application. Inherent to this abbreviated approval process, intranasal nalmefene was not studied in patients currently suffering opioid overdose.

NALOXONE AND NALMEFENE

Nalmefene also has unique characteristics compared with naloxone, the current standard opioid antidote. Nalmefene has a higher affinity for opioid receptors and a longer duration of action than naloxone. Comparative effectiveness data regarding naloxone and nalmefene are sparse, and it is unclear if the inherent properties of nalmefene are beneficial in opioid overdose. We have decades of experience using naloxone safely and effectively as the primary opioid antidote, even in cases of fentanyl and fentanyl analog overdoses. There is, however, evidence to suggest nalmefene may result in more prolonged and severe opioid withdrawal than naloxone, which could be harmful to patients.

POSITION

As nalmefene is untested in the current clinical environment of synthetic opioid overdoses and has the potential to cause harm via prolonged withdrawal, it is the opinion of the American College of Medical Toxicology and the American Academy of Clinical Toxicology that nalmefene should not replace naloxone as the primary opioid antidote at this time.

RECOMMENDATIONS

We recommend additional clinical studies of nalmefene, administered via all approved routes, be conducted in a comparative fashion with naloxone, and that safety and effectiveness outcomes be evaluated before nalmefene is recommended as a primary opioid antidote.

Opioid antagonists with minimal sedation for opioid withdrawal

BACKGROUND

Managed withdrawal is a necessary step prior to drug-free treatment or as the end point of long-term substitution treatment.

OBJECTIVES

To assess the effectiveness of opioid antagonists in combination with minimal sedation to manage opioid withdrawal.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 3, 2008), MEDLINE (January 1966-July 2008), EMBASE (January 1985-2008 Week 31), PsycINFO (1967 to 7 August 2008) and reference lists of articles.

SELECTION CRITERIA

Controlled studies of interventions involving the use of opioid antagonists in combination with minimal sedation to manage withdrawal in opioid-dependent participants compared with other approaches or different opioid antagonist regimes.

DATA COLLECTION AND ANALYSIS

One author assessed studies for inclusion and undertook data extraction. Inclusion decisions and the overall process were confirmed by consultation between all authors.

MAIN RESULTS

Nine studies (6 randomised controlled trials), involving 837 participants, met the inclusion criteria for the review.The quality of the evidence is low, but suggests that withdrawal induced by opioid antagonists in combination with an adrenergic agonist is more intense than withdrawal managed with clonidine or lofexidine alone, while the overall severity is less. Delirium may occur following the first dose of opioid antagonist, particularly with higher doses (> 25mg naltrexone).In some situations antagonist-induced withdrawal may be associated with significantly higher rates of completion of treatment, comp[ared to withdrawal managed primarily with adrenergic agonists. However, this outcome has not been produced consistently, and the extent of any benefit is highly uncertain.

AUTHORS' CONCLUSIONS

The use of opioid antagonists combined with alpha(2)-adrenergic agonists is a feasible approach to the management of opioid withdrawal. However, it is unclear whether this approach reduces the duration of withdrawal or facilitates transfer to naltrexone treatment to a greater extent than withdrawal managed primarily with an adrenergic agonist.A high level of monitoring and support is desirable for several hours following administration of opioid antagonists because of the possibility of vomiting, diarrhoea and delirium.Further research is required to confirm the relative effectiveness of antagonist-induced regimes, as well as variables influencing the severity of withdrawal, adverse effects, the most effective antagonist-based treatment regime, and approaches that might increase retention in subsequent naltrexone maintenance treatment.

Emergency management of inadvertent accelerated opiate withdrawal in dependent opiate users

Six opiate-dependent drug users presented to the local emergency department within a 10-day period with symptoms of severe opioid withdrawal immediately following intravenous use of recently acquired street 'heroin'. The withdrawal picture was similar to that described in patients undergoing rapid opioid detoxification, suggesting that the substance injected was contaminated with an opiate antagonist. A number of potential compounds are discussed, including naltrexone and buprenorphine, and recommendations for the medical management of severe opiate withdrawal within an emergency setting are outlined. [Lubman DI, Koutsogiannis Z, Kronborg I. Emergency management of inadvertent accelerated opiate withdrawal in dependent opiate users.

Opioid antagonists with minimal sedation for opioid withdrawal

BACKGROUND

Managed withdrawal is necessary prior to drug-free treatment. It may also represent the end point of long-term opioid replacement treatment.

OBJECTIVES

To assess the effectiveness of opioid antagonists in combination with minimal sedation to induce withdrawal, in terms of intensity of withdrawal, adverse effects and completion of treatment.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 3, 2005, which includes the Cochrane Drugs and Alcohol Group register), MEDLINE (January 1966 to August 2005), EMBASE (January 1985 to August 2005), PsycINFO (1967 to August 2005), and CINAHL (1982 to July 2005) and reference lists of articles.

SELECTION CRITERIA

Experimental interventions involved the use of opioid antagonists in combination with minimal sedation to manage withdrawal in opioid-dependent participants compared with other approaches or different opioid antagonist regime.

DATA COLLECTION AND ANALYSIS

One reviewer assessed studies for inclusion and undertook data extraction and trial quality. Study authors were contacted for additional information.

MAIN RESULTS

Nine studies (5 randomised controlled trials), involving 775 participants, met the inclusion criteria for the review. Withdrawal induced by opioid antagonists in combination with an adrenergic agonist is more intense than withdrawal managed with clonidine or lofexidine alone, but the overall severity is less. Limited data showed that antagonist-induced withdrawal may be more severe when the last opioid used was methadone rather than heroin or another short-acting opioid. Delirium may occur following the first dose of opioid antagonist, particularly with higher doses (> 25mg naltrexone). The studies included suggest there is no significant difference in rates of completion of treatment for withdrawal induced by opioid antagonists, in combination with an adrenergic agonist, compared with adrenergic agonist alone.

AUTHORS' CONCLUSIONS

The use of opioid antagonists combined with alpha2 adrenergic agonists is a feasible approach to the management of opioid withdrawal. However, it is unclear whether this approach reduces the duration of withdrawal or facilitates transfer to naltrexone treatment to a greater extent than withdrawal managed primarily with an adrenergic agonist.A high level of monitoring and support is desirable for several hours following administration of opioid antagonists because of the possibility of vomiting, diarrhoea and delirium. Further research is required to confirm the relative effectiveness of antagonist-induced regimes, as well as variables influencing the severity of withdrawal, adverse effects, the most effective antagonist-based treatment regime, and approaches that might increase retention in subsequent naltrexone maintenance treatment.

Lofexidine for opiate detoxification

The evolving role for lofexidine in the treatment of opiate detoxification over the last decade is reviewed. Lofexidine is no better than methadone or clonidine in attenuating withdrawal symptom severity, although it has a more favourable side-effect profile than clonidine. In conjunction with opiate antagonists, lofexidine may facilitate accelerated withdrawal, although activity and low liability for misuse, lofexidine may be more widely acceptable to clinicians than methadone, particularly those working in out-patient, non-specialist and prison treatment settings. Further studies in these treatment settings will be particularly apposite since, apart from the studies highlighted, the evidence base for the clinical value of lofexidine is mainly to be derived from in-patient trials.

Major disruptions of sleep during treatment of the opiate withdrawal syndrome: differences between methadone and lofexidine detoxification treatments

Sleep disturbance experienced during methadone or lofexidine opiate detoxification was investigated in 118 opiate-dependent patients receiving inpatient detoxification treatment. Sleep was assessed at four time-points during opiate detoxification using a self-report questionnaire. Maximum sleep disruption occurred at completion of detoxification and during the protracted withdrawal period, with patients in the methadone group reporting higher levels of withdrawal symptoms, lower overall sleep, longer sleep latencies and significantly longer periods of time awake than lofexidine patients. Regression analyses demonstrated a significant relationship between sleep disturbance, protracted withdrawal and retention in treatment, in addition to the major treatment benefit of reduced sleep disturbance conferred by lofexidine treatment.

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.

Naltrexone and lofexidine combination treatment compared with conventional lofexidine treatment for in-patient opiate detoxification

This study compares a naltrexone/lofexidine combination treatment with a 7-day course of lofexidine alone in the treatment of opiate withdrawal in 22 opiate-dependent patients. Withdrawal symptoms were significantly less severe on days 4-7, and 9-13, in the naltrexone/lofexidine combination group. There were no significant differences in the percentage of patients completing detoxification or in the mean length of stay for the two groups. Both treatments had similar, minimal effects on blood pressure. The naltrexone/lofexidine combination was associated with a more rapid resolution of the opiate withdrawal syndrome than a 7-day lofexidine-only treatment schedule, without substantial increases in withdrawal symptoms or hypotensive side-effects.