Mechanism of Action
VIP acts through two main G-protein coupled receptors: VPAC1 (ubiquitous) and VPAC2 (brain, smooth muscle, immune cells).
cAMP-Mediated Anti-inflammatory Signaling
VPAC1/VPAC2 activation elevates intracellular cAMP, which inhibits NF-kB, reduces pro-inflammatory cytokine production (TNF-alpha, IL-6, IL-12, IFN-gamma), and upregulates anti-inflammatory mediators (IL-10, TGF-beta). VIP simultaneously reduces Th1 differentiation and promotes Th2/Treg balance, shifting immune responses toward tolerance.[1]Vasodilation and Pulmonary Circulation
VIP is a potent vasodilator in pulmonary, mesenteric, and cerebral vasculature via cAMP-mediated smooth muscle relaxation. This effect is the basis for its investigation in pulmonary arterial hypertension, inhaled VIP reduces pulmonary vascular resistance acutely.[2]Neuroprotection and BDNF
VIP promotes neuronal survival, BDNF secretion, and neurogenesis in hippocampal and cortical neurons. It protects against oxidative stress, excitotoxicity, and inflammatory neuronal death. VPAC2 in the SCN (circadian pacemaker) plays a key role in circadian rhythm maintenance.[3]Research Overview
Autoimmune Disease (RA, MS)
Phase II ClinicalPhase II trial of VIP in rheumatoid arthritis (IV, 22 patients): significant reduction in disease activity scores, inflammatory cytokines, and pain scores versus placebo. Multiple sclerosis and inflammatory bowel disease animal models show VIP reduces disease severity via Treg promotion and Th17 suppression.[1]
Pulmonary Arterial Hypertension
Phase II ClinicalInhaled VIP (200 mcg 3x daily) in a Phase II trial showed reduced pulmonary artery pressure, improved 6-minute walk distance, and better exercise tolerance. VIP deficiency has been identified in PAH patient lung tissue, suggesting it plays a protective physiological role.[2]
CIRS and Post-Viral Syndromes
EmergingVIP deficiency is a documented finding in Chronic Inflammatory Response Syndrome (CIRS) and long COVID. VIP restoration (intranasal protocols) is used in CIRS protocols developed by Dr. Ritchie Shoemaker based on observed VIP deficiency in affected patients and reported clinical improvement with replacement therapy.[4]
Calculate your VIP dose Vial strength, BAC water, exact syringe draw in IU. Free, no signup. Open Calc →
Research Protocols
| Goal | Dose | Frequency | Route |
|---|---|---|---|
| Anti-inflammatory / autoimmune | 50–100 µg | Once or twice daily | Subcutaneous |
| CIRS protocol (Shoemaker) | 50 µg 4× daily (intranasal) | 4× daily | Intranasal |
| Pulmonary (inhaled, clinical) | 200 µg | 3× daily | Inhaled |
Intranasal allows direct CNS access. CIRS protocols use intranasal 4x daily. Very short plasma half-life requires frequent dosing for sustained systemic effects; subcutaneous depot extends duration somewhat versus IV.
Research protocols only. Not medical advice.
Peptide Interactions
Safety Profile
VIP has Phase II clinical safety data from RA and PAH trials.
Blood pressure: VIP is a vasodilator, transient hypotension can occur, particularly with IV or high-dose subcutaneous administration. Start low.
Flushing: Vasodilation produces transient flushing, especially with subcutaneous injections above 100 mcg.
Short half-life: Very short plasma half-life limits systemic effects. This reduces toxicity risk but also limits efficacy duration per dose.
No FDA approval: Research compound for most applications. Inhaled form has been in Phase II trials.
References
- [1]Delgado M, et al. "VIP and PACAP inhibit activation of inflammatory immune responses." Ann N Y Acad Sci. 2006;1070:51-65.
- [2]Petkov V, et al. "Vasoactive intestinal peptide as a new drug for treatment of primary pulmonary hypertension." J Clin Invest. 2003;111(9):1339-1346.
- [3]Waschek JA. "VIP and PACAP: neuropeptide modulators of CNS inflammation, injury, and repair." Br J Pharmacol. 2013;169(3):512-523.
- [4]Shoemaker RC, House D, Ryan JC. "Vasoactive neuropeptide dysregulation in patients with Chronic Inflammatory Response Syndrome." In Vivo. 2010;24(4):493-501.