Metenkefalin

Endogenous Opioid Peptide (enkephalin)Rx: ResearchCompound: Research

Also known as: [Met5]-enkephalin, MENK, Met-enkephalin, Methionine enkephalin, Tyr-Gly-Gly-Phe-Met

Educational Only — Not medical advice. Consult a qualified clinician before using any peptide.

Summary

Metenkefalin (Met-enkephalin) is an endogenous pentapeptide (Tyr-Gly-Gly-Phe-Met) belonging to the enkephalin family of opioid peptides. It is naturally produced in the adrenal medulla and distributed throughout the CNS. It has been investigated for immunomodulatory effects, particularly in HIV/AIDS and cancer, and for analgesic properties. It is not approved as a therapeutic agent in any major jurisdiction but has been explored in clinical trials.

Mechanism of Action

Agonist at delta-opioid receptors (DOR) and mu-opioid receptors (MOR); modulates pain signaling, immune function, and neuroendocrine activity by binding to opioid receptors in the central and peripheral nervous systems.

Routes of Administration

IntranasalIntravenousOralSubcutaneous

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

No sources recorded yet.

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