Emergency management of inadvertent accelerated opiate withdrawal in dependent opiate users

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The injection formulation, which had been withdrawn in 2008, was reintroduced in 2022, and in 2023 the United States Food and Drug Administration approved a new intranasal formulation of nalmefene.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 Withdrawal Precipitated by Long-Acting Antagonists

BACKGROUND

Precipitated opioid withdrawal (POW) after opioid antagonist administration can be challenging to manage in the emergency department (ED), particularly if caused by a long-acting opioid antagonist such as naltrexone. There are no evidence-based guidelines to assist in safely and efficiently managing patients with this syndrome.

OBJECTIVE OF REVIEW

To review current practice on the treatment of long-acting antagonist POW and make recommendations on the treatment of this complex disease process.

METHODS

A literature search of opioid withdrawal cases precipitated by naltrexone was done using PubMed. One of the authors screened all the results of this search by title and abstract, leading to a final count of 27 articles that were reviewed in full by all authors. English language cases that involved precipitated opioid withdrawal from a long-acting opioid antagonist were included. Data were extracted, including the precipitant involved and dose, severity of opioid withdrawal, treatments rendered, and response to treatment. In all cases where symptoms and signs were described, a Clinical Opiate Withdrawal Scale score was calculated based on the information available.

RESULTS

Twenty-seven papers were included. Naltrexone alone was the primary antagonist reported in 19 of the papers, extended-release naltrexone in two, naltrexone-morphine combination in two, and nalmefene in four. Treatment most commonly included fluid replacement, benzodiazepines, antiemetics, and clonidine. Full opioid agonist treatment, although often suggested, was poorly described. Buprenorphine successfully reduced the severity and duration of withdrawal in several cases. No standardized response scale was used, and response to treatment ranged from 3 to 48 h prior to resolution of clinical effects.

CONCLUSIONS

Management of POW from long-acting antagonists is a complex problem with little formal evaluation of treatment options. There is not currently a sufficiently robust body of literature to support an evidence-based guideline. However, use of intravenous fluids, antiemetics, and benzodiazepines is commonly reported as successful and seems to be a reasonable approach until this process is better studied. A treatment strategy using partial agonists such as buprenorphine is emerging and may represent a safe and effective treatment pathway for these patients.

Potential uses of naltrexone in emergency department patients with opioid use disorder

Introduction: Despite widespread recognition of the opioid crisis, opioid overdose remains a common reason for Emergency Department (ED) utilization. Treatment for these patients after stabilization often involves the provision of information for outpatient treatment options. Ideally, an ED visit for overdose would present an opportunity to start treatment for opioid use disorder (OUD) immediately. Although widely recognized as effective, opioid agonist therapy with methadone and buprenorphine commonly referred to as "medication-assisted therapy" but more correctly as "medication for addiction treatment" (MAT), can be difficult to access even for motivated individuals due to shortages of prescribers and treatment programs. Moreover, opioid agonist therapy may not be appropriate for all patients, as many patients who present after overdose are not opioid dependent. More treatment options are required to successfully match patients with diverse needs to an optimal treatment plan in order to avoid relapse. Naltrexone, a long-acting opioid antagonist, available orally and as a monthly extended-release intramuscular injection, may represent another treatment option. Methods: We conducted a literature search of MEDLINE and PubMed. We aimed to capture references related to naltrexone and is use as MAT for OUD, as well as manuscripts that discussed naltrexone in comparison toother agents used for MAT, opioid detoxification, and naltrexone metabolism. Our initial search logic returned a total of 618 articles. Following individual evaluation for relevance, we selected 65 for in-depthreview. Manuscripts meeting criteria were examined for citations meriting further review, leading to the addition of 30 manuscripts Conclusions: Here, we review the pharmacology of naltrexone as it relates to OUD, its history of use, and highlight recent studies and new approaches for use of the drug as MAT including its potential initiation after ED visit for opioid overdose.

Withdrawal syndrome caused by naltrexone in opioid abusers

STUDY OBJECTIVE

Naltrexone is a competitive opioid receptor antagonist acting at the µ- and k-opioid receptors that blocks the euphoric effects of exogenous administered opioids. When used in opioid-dependent patients, naltrexone can cause acute and severe withdrawal symptoms.

METHODS

This was a cross-sectional study conducted from December 2007 to March 2008 and consisted of patients who had used naltrexone accidentally or deliberately and were referred to Loghman-Hakim Poison Hospital, Tehran, Iran. All symptoms and signs were assessed and the relationship between the dose of naltrexone, opioid dependence, and outcome was evaluated.

RESULTS

In 132 patients referred to our hospital, the most frequently reported symptoms and signs occurring in more than 10% of patients were agitation (96.2%), altered level of consciousness (38.6%), nausea (28%), vomiting (27.3%), abdominal pain (24.2%), diarrhea (16.7%), bone and muscle pain (15.9%), tachycardia (12.9%), and dilated pupils (11.4%). Being the most prominent symptom, the agitation was the most difficult aspect of withdrawal to manage. Except for agitation, no relationship was found between the presence of these symptoms and the dose of naltrexone used. Outcome of the patients (classified as complete recovery, partial recovery, death, and no follow-up) was related to the substance of addiction (p < 0.05) but not to the naltrexone dose.

CONCLUSION

Emergency physicians should be aware of the potential for severe agitation from naltrexone-precipitated hyperacute withdrawal and its appropriate management. Opioid-dependent patients who wish to continue withdrawal and abstinence must be encouraged to visit trained physicians and be warned about misuse of naltrexone.