Metenkefalin
Also known as: [Met5]-enkephalin, MENK, Met-enkephalin, Methionine enkephalin, Tyr-Gly-Gly-Phe-Met
Source Metenkefalin at Peptiology
Save 10% with code PEPTI-BOSSRABBIT-10
Affiliate link: we earn a commission on purchases made through this link, at no extra cost to you.
Tapping Shop Now & Save 10% copies your 10% off code PEPTI-BOSSRABBIT-10 to your clipboard. Paste it at the Peptiology checkout to claim the discount.
Summary
Metenkefalin, also called Met‑enkephalin, is an endogenous opioid peptide belonging to the enkephalin family. It is investigated primarily as a research tool rather than a marketed drug. Studies have examined its levels in neurological conditions, its experimental use as an immunomodulator in COVID‑19 protocols, and its physiological actions such as prolactin release in animal models.
Mechanism of Action
Metenkefalin binds to opioid receptors, especially the delta (δ) and mu (μ) subtypes, modulating neuronal signaling and pain pathways. In addition to classic opioid effects, animal work suggests it can trigger prolactin secretion through a prostaglandin‑mediated cascade that can be blocked by indomethacin. These actions underlie its potential neuromodulatory and immunomodulatory roles observed in experimental settings.
What the Research Shows
Human data are limited to observational reports. One case of dopa‑responsive dystonia showed reduced cerebrospinal fluid metenkefalin, indicating broader neurotransmitter disruption. In a COVID‑19 therapeutic protocol, metenkefalin/tridecactide was administered alongside corticosteroids, but the published results highlighted only steroid effects, providing no efficacy signal for the peptide. A double‑blind NADH trial in Parkinson's patients measured metenkefalin levels before and after treatment and found no biochemical or clinical changes. In rats, a synthetic analogue (MET‑ENH‑NH2) induced prolactin release, an effect attenuated by indomethacin, suggesting a prostaglandin link. Overall, evidence is confined to small, often ancillary measurements rather than definitive therapeutic outcomes.
Reported Benefits
Current evidence does not demonstrate clear therapeutic benefits of metenkefalin in humans. Observational studies note its presence as a biomarker of neurotransmitter status, and animal experiments reveal a capacity to stimulate prolactin release, which may inform endocrine research. No robust clinical advantage has been established.
Limitations of the Evidence
The literature is sparse, with small sample sizes, lack of control groups, and mostly indirect measurements. COVID‑19 and Parkinson's studies did not report significant effects attributable to metenkefalin. Animal findings may not translate to human physiology. Consequently, conclusions about efficacy, dosing, or safety remain premature.
Safety Considerations
No adverse event data for metenkefalin are reported in the cited human studies. Animal work indicates it can influence prolactin secretion, a hormonal effect that could have physiological implications. Without systematic safety assessments, potential risks in humans remain undefined, and caution is warranted in experimental use.
How It Is Administered
In research settings metenkefalin has been delivered by intranasal, intravenous, oral, and subcutaneous routes. Formulations are typically peptide solutions appropriate for the chosen route, but no standardized pharmaceutical product exists.
Routes of Administration
Goals & Uses
- Anti-tumor activityOncologyLow
- ImmunomodulationImmunologyLow
- Mood and stress modulationNeuropsychiatryLow
- AnalgesiaPain ManagementLow
Contraindications
- Known hypersensitivity to enkephalins or opioid peptidesAllergyHigh
- Concurrent use of opioid antagonistsDrug InteractionModerate
- Respiratory depression riskPulmonaryModerate
Adverse Effects
- Injection site reactionsLocalCommon
- HypotensionCardiovascularUncommonLow blood pressure
- NauseaGastrointestinalUncommonFeeling of sickness or urge to vomit
- SedationCNSUncommon
Drug Interactions
- Enkephalinase inhibitors (e.g., thiorphan)Moderate
- Naloxone / NaltrexoneHigh
- CNS depressants (benzodiazepines, barbiturates)Moderate
Population Constraints
- PregnancyReproductive SafetyRelative
- Pediatric populationsAgeRelative
- Severe hepatic or renal impairmentOrgan ImpairmentRelative
- Opioid use disorder historyPsychiatric/Substance UseRelative
Regulatory Status
- European UnionUnapprovedNot approved by EMA. No active marketing authorization applications on record.
- United StatesUnapprovedNot FDA-approved. Investigated under IND protocols in HIV/AIDS and oncology contexts in the 1980s–1990s. Currently a research compound.
- United KingdomUnapprovedNot approved by MHRA. Remains a research-only compound.
Not approved by FDA, EMA, or MHRA as a drug. Has been investigated in clinical settings (e.g., under the name Methionine enkephalin or TNX-355 context not applicable; studied under IND protocols). Marketed illicitly in some jurisdictions under names like 'Opiorphin' or 'MENK'; regulatory oversight is limited.
Evidence & Sources
- Journal ArticleLowOlsson JE, et al.1992-01-01T00:00:00.000000Z
- Journal ArticleLowOmerovic N, et al.2023-01-01T00:00:00.000000Z
- Journal ArticleModerateDizdar N, Kågedal B, Lindvall B1994-01-01T00:00:00.000000Z
- Journal ArticleLowCosta G, et al.1979-01-01T00:00:00.000000Z
Frequently Asked Questions
What type of compound is metenkefalin?
Metenkefalin is an endogenous opioid peptide, specifically an enkephalin, that naturally occurs in the brain and interacts with opioid receptors to modulate neuronal signaling.
Has metenkefalin been proven effective for any disease?
No. Human studies to date have not shown statistically significant clinical benefits for conditions such as Parkinson's disease or COVID‑19, and the evidence remains limited to observational and biochemical measurements.
Can metenkefalin be used safely in humans?
Safety data are lacking. The cited literature does not report adverse events, but potential hormonal effects (e.g., prolactin release) have been observed in animals, indicating that systematic safety evaluation is needed before clinical use.
How is metenkefalin administered in research?
Researchers have administered metenkefalin via intranasal, intravenous, oral, and subcutaneous routes, typically using peptide solutions suitable for each delivery method.
Does metenkefalin affect prolactin levels?
In rats, a synthetic analogue of metenkefalin (MET‑ENH‑NH2) stimulated prolactin release, an effect that could be blocked by indomethacin, suggesting involvement of prostaglandin pathways.
What is Metenkefalin?
Metenkefalin, also called Met‑enkephalin, is an endogenous opioid peptide belonging to the enkephalin family. It is investigated primarily as a research tool rather than a marketed drug. Studies have examined its levels in neurological conditions, its experimental use as an immunomodulator in COVID‑19 protocols, and its physiological actions such as prolactin release in animal models.
What is Metenkefalin used for?
Metenkefalin is educationally associated with: Anti-tumor activity, Immunomodulation, Mood and stress modulation, Analgesia. Educational only — not medical advice.
How is Metenkefalin administered?
Recorded routes of administration: Intranasal, Intravenous, Oral, Subcutaneous.
What are the potential side effects of Metenkefalin?
Reported adverse effects include: Injection site reactions, Hypotension, Nausea, Sedation. This list is not exhaustive — consult a qualified clinician.
Who should avoid Metenkefalin?
Recorded contraindications: Known hypersensitivity to enkephalins or opioid peptides, Concurrent use of opioid antagonists, Respiratory depression risk. Consult a qualified clinician before use.