Side-by-Side Comparison · 2026

Endomorphin-1 vs Endomorphin-2

Endomorphin-1 vs Endomorphin-2 — mechanism, half-life, dosing, and research status compared. Which is right for your protocol?

Endomorphin-1
Endogenous Opioid / Mu Selective

Endomorphin-1 (Tyr-Pro-Trp-Phe-NH2) is a tetrapeptide amide isolated from bovine frontal cortex and proposed as an endogenous mu opioid receptor (MOR) ligand with the highest known selectivity for MOR among any endogenous opioid peptide. Unlike enkephalins and endorphins that act...

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Endomorphin-2
Endogenous Opioid / Mu Selective

Endomorphin-2 (Tyr-Pro-Phe-Phe-NH2) is the second member of the endomorphin family, differing from endomorphin-1 by a single residue (Phe for Trp at position 3). Both share extraordinary MOR selectivity (>4000-fold over delta and kappa opioid receptors), but their neuroanatomical...

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Key Parameters
Parameter Endomorphin-1 Endomorphin-2
Category Endogenous Opioid / Mu Selective Endogenous Opioid / Mu Selective
Research Research / Endogenous Peptide Research / Endogenous Peptide
Half-Life 1-5 minutes (plasma; rapid enzymatic degradation) 1-5 minutes (plasma)
Typical Dose Research: 1-10 nmol intrathecal; 10-100 nmol ICV (rodent) Research: 1-10 nmol intrathecal; 10-100 nmol ICV (rodent)
Frequency Endogenous: activity-dependent; research per session Per research session
Route Endogenous (CNS); research intrathecal/ICV/SC Endogenous (spinal cord, brainstem); research intrathecal/ICV
FDA Status Not approved; research peptide Not approved; research peptide

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Frequently Asked Questions
What is the difference between Endomorphin-1 and Endomorphin-2?
Endomorphin-1: Endomorphin-1 (Tyr-Pro-Trp-Phe-NH2) is a tetrapeptide amide isolated from bovine frontal cortex and proposed as an endogenous mu opioid receptor (MOR) ligand with the highest known selectivity for MOR... Endomorphin-2: Endomorphin-2 (Tyr-Pro-Phe-Phe-NH2) is the second member of the endomorphin family, differing from endomorphin-1 by a single residue (Phe for Trp at position 3). Both share extraordinary MOR selectivi...
Which has a longer half-life, Endomorphin-1 or Endomorphin-2?
Endomorphin-1 half-life: 1-5 minutes (plasma; rapid enzymatic degradation). Endomorphin-2 half-life: 1-5 minutes (plasma).
Can you stack Endomorphin-1 and Endomorphin-2?
Endomorphin-1 and Endomorphin-2 are in the same category and used together in research protocols. Always consult relevant literature and follow appropriate guidelines.

For research use only. Not medical advice. ASCEND does not conduct or endorse any specific research protocol. Always consult relevant scientific literature and regulatory guidelines.