Opioid Peptides
6 compounds in this family, each with its recorded mechanism, routes of administration, safety notes and references to published literature.
- CR665CR665 (also known as FE‑200665) is an investigational peptide that selectively activates kappa‑opioid receptors located on peripheral sensory nerves. Developed to provide analgesia—particularly for visceral and other peripheral pain—its design limits entry into the central nervous system, aiming to avoid typical opioid‑related side effects such as sedation, respiratory depression, and addiction.
- DADLEDADLE ([D-Ala2, D-Leu5]-enkephalin) is a synthetic peptide that selectively activates delta‑opioid receptors (DORs). In preclinical research it has been investigated as a neuroprotective and organ‑preserving agent for conditions such as stroke, traumatic brain injury, hemorrhagic shock, and neurodegenerative models. The peptide also induces pharmacological hypothermia, a state resembling natural hibernation, which may contribute to its protective effects. DADLE remains a research‑only compound and has not been approved for clinical use.
- DPDPEDPDPE (Tyr-[D‑Pen‑Gly‑Phe‑D‑Pen]) is a cyclic peptide that acts as a selective agonist at delta‑opioid receptors. It is employed in pre‑clinical research to explore delta‑opioid signalling, receptor regulation, and reward mechanisms. Studies have examined its structural conformation, its lack of antitussive activity, and its reinforcing properties when injected into brain reward sites.
- DynorphinDynorphin is an endogenous opioid peptide belonging to the dynorphin family. It acts primarily as an agonist at κ‑opioid receptors and is found throughout the central nervous system. Research links dynorphin to the regulation of pain, stress, sleep, and reproductive hormone release, and it is investigated in contexts such as menopause‑related sleep disturbance, addiction neurocircuitry, and opioid‑induced hyperalgesia. The peptide is currently a research tool rather than an approved therapeutic.
- MetenkefalinMetenkefalin, 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.
- MetkephamidMetkephamid is a synthetic analogue of the endogenous opioid peptide methionine enkephalin, classified as a delta‑opioid receptor agonist. It has been explored in research settings for acute analgesia, particularly after surgery or postpartum episiotomy. Clinical trials using single parenteral doses (70–140 mg) reported pain relief comparable to the conventional opioid pethidine, with the higher dose showing the greatest efficacy. The compound remains investigational and is not approved for routine clinical use.