Substance P

Substance P — Tachykinin Neuropeptide

Evidence & Status

  • Moderate Evidence
  • Established

At a Glance

An 11-amino-acid, C-terminally amidated neuropeptide central to pain-signaling research. Direct human studies show it can induce headache/vascular effects and skin inflammation when administered; NK1 receptor antagonists that block its signaling are FDA-approved for chemotherapy-induced nausea, though not for pain.

Plain English

Researchers study Substance P because it's one of the nervous system's key pain-signaling chemicals. In human studies, giving people Substance P through an IV can trigger headache and blood-vessel dilation, and injecting it into skin causes local inflammation — useful for understanding these processes but not evidence that Substance P itself is a treatment. Drugs that block its receptor (NK1 antagonists) are approved to prevent nausea from chemotherapy, showing this pathway can be targeted with medication — though that particular drug's dosing has nothing to do with Substance P.

Overview

Substance P (SP) is an 11-amino-acid, C-terminally amidated (RPKPQQFFGLM-NH2) tachykinin neuropeptide produced throughout the central and peripheral nervous system, as well as by immune cells, enteroendocrine cells, and endothelium. Discovered in 1931 by Ulf von Euler and John Gaddum, it was one of the first neuropeptides identified. It signals primarily through NK1 receptors and is studied as a mediator of pain transmission, neurogenic inflammation, nausea/vomiting, and immune modulation. In a small (n=6) human intradermal-challenge study, Substance P produced neurogenic skin inflammation (Grouzmann et al., 2011). In a 2025 randomized, placebo-controlled crossover study, IV Substance P infusion induced headache and vascular dilation in healthy volunteers more often than placebo (15/21 vs. 2/21) (Al-Khazali et al., 2025) — a healthy-volunteer physiology finding, not evidence of a migraine treatment or of chronic pain efficacy. A CSF biomarker study in medication-free PTSD outpatients found Substance P levels similar to controls (Bonne et al., 2011), not the elevated or severity-correlated levels sometimes claimed. NK1 receptor antagonists (aprepitant/Emend, netupitant/Akynzeo) developed to block Substance P signaling are FDA-approved — not for pain, but for chemotherapy-induced nausea and vomiting (CINV); aprepitant's 125 mg oral dose is a dose of that different drug, not of Substance P. Substance P also activates NK1 receptors on mast cells and macrophages, the mechanistic basis proposed for neurogenic inflammation.

Research Summary

Substance P has an extensive mechanistic literature and a well-validated NK1 receptor pathway. Direct human evidence is more limited than the mechanistic literature might suggest: a small (n=6) intradermal-challenge study demonstrated neurogenic skin inflammation, and a 2025 randomized, placebo-controlled crossover trial found that IV Substance P reliably induced headache and vascular dilation in healthy volunteers — useful for headache-pathophysiology research but not evidence of therapeutic or migraine-treatment efficacy. A CSF biomarker study in PTSD found Substance P levels similar between patients and controls, correcting an earlier claim of elevated or severity-correlated levels. The clearest human translational success is indirect: NK1 receptor antagonists (aprepitant, netupitant) are FDA-approved for chemotherapy-induced nausea and vomiting, demonstrating that the SP-NK1R axis is druggable — but this is evidence about NK1 antagonism, not about administering Substance P itself, and the antagonist's dosing does not apply to Substance P.

Research Areas

  • Pain neuroscience
  • Neurogenic inflammation
  • Anxiety and PTSD
  • Nausea and vomiting
  • Mast cell activation
  • Airway inflammation
  • Gut motility

Safety & Risks

Serious Risks

  • Not directly applicable as a therapeutic agent; see NK1 antagonist entries for therapeutic risk profiles

Reported Side Effects

  • When endogenously elevated or exogenously administered: vasodilation, plasma extravasation, bronchoconstriction, potentiated pain signaling
United States
Research only; not approved for human therapeutic use; NK1 receptor antagonists that block Substance P signaling (aprepitant, netupitant) are FDA-approved
United Kingdom
Research only; NK1 antagonists are MHRA-approved for CINV
Australia
Research only
Canada
Research only

Citations & Sources