Naltrexone Hydrochloride

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Cat Number

API0232108

CAS Number

16676-29-2

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CAS Number

16676-29-2

EINECS

240-723-0

Synonyms

Naltrexone HCl

Molecular Formula

C20H23NO4·HCl

Molecular Weight

377.86

Smiles

C1CC1CN2CC[C@]34[C@@H]5C(=O)CC[C@]3([C@H]2CC6=C4C(=C(C=C6)O)O5)O.Cl

Appearance

White, crystalline compound

Boiling Point

558.1℃

General Description

Naltrexone hydrochloride is the hydrochloride salt of naltrexone, a synthetic noroxymorphone derivative with competitive opioid antagonist activity. FDA-approved since 1984, it is a Schedule II controlled substance used as part of comprehensive treatment programs.

Mechanism of Action

Naltrexone exerts its pharmacological effects by competitively binding to and blocking mu-opioid receptors, with weaker antagonist activity at kappa and delta-opioid receptors. By occupying these receptors, it prevents exogenous opioids from producing euphoria, analgesia, sedation, and physical dependence.

Application

Naltrexone hydrochloride is FDA-approved for alcohol use disorder to reduce heavy drinking and for opioid dependence to prevent relapse in detoxified, opioid-free individuals highly motivated to maintain abstinence.

Rassi-Mariani V, et al. evaluated the efficacy of low-dose naltrexone (LDN) for the treatment of chronic pain. The authors conducted a systematic search of PubMed, Scopus, Cochrane CENTRAL, and EMBASE databases, identifying seven randomized clinical trials involving 406 patients. The dosage range across all studies was 2 to 4.5 mg once daily, and various chronic pain conditions were assessed. The results indicated that low-dose naltrexone was ineffective in managing chronic pain or improving quality of life in patients with different chronic pain conditions.

Fig. 1 Flowchart of included studies (Rassi-Mariani V, et al., 2024)

References

Rassi-Mariani V, et al. The use of naltrexone in the treatment of chronic pain: a systematic review. Pain Manag. 2024;14(8):453-463.

Magane KM, et al. compared the effectiveness of initiating oral naltrexone versus extended-release injectable naltrexone in 248 hospitalized patients with alcohol use disorder and recent heavy drinking. At 3-month follow-up, both groups showed substantial reductions in heavy drinking days (oral: –38.4 percentage points; injectable: –46.4 percentage points), with no significant between-group difference. Similarly, rates of acute health care utilization (emergency department visits or hospitalizations) were comparable between groups (oral 54.1%, injectable 61.1%).

Fig. 2 Outcomes for oral vs Extended-Release (ER) injectable naltrexone among patients with alcohol use disorder (N = 248). (Magane KM, et al, 2025)

References

Magane KM, et al. Oral vs Extended-Release Injectable Naltrexone for Hospitalized Patients With Alcohol Use Disorder: A Randomized Clinical Trial. JAMA Intern Med. 2025;185(6):635-645.

Does Naltrexone Hydrochloride require protection from light during storage?

Yes, prolonged exposure to light can lead to photodegradation. It should be stored in light-resistant containers, away from direct sunlight or strong UV sources.

What is the recommended long-term storage temperature for Naltrexone Hydrochloride?

Controlled room temperature (20-25°C) is suitable. Avoid storage above 30°C or in high-humidity environments to maintain its crystalline structure and purity.

Is Naltrexone Hydrochloride compatible with common tablet excipients for formulation?

Yes, it shows good compatibility. However, we recommend conducting pre-formulation studies with specific excipients, and we can provide compatibility data upon request.

How is the impurity profile of Naltrexone Hydrochloride monitored over its shelf life?

We specifically track the formation of naltrexone-related compound B using a stability-indicating HPLC method, ensuring levels remain within ICH limits.