VIP

Vasoactive intestinal peptide is a 28-amino-acid endogenous neuropeptide hormone produced throughout the gut, pancreas, and central nervous system, and distributed across peripheral nerves, the immune system, lungs, and cardiovascular system. It is part of the neuroendocrine immune network, the bidirectional signalling system shared by the nervous and immune systems.

It is a regulatory peptide acting through the G protein-coupled receptors VPAC1 and VPAC2 and downstream cAMP signalling, with effects spanning vasodilation, smooth muscle relaxation, immune modulation, neuroprotection, circadian regulation, and anti-inflammatory cytokine balance. It is regarded as one of the strongest endogenous anti-inflammatory peptides and is explicitly distinguished from corticosteroids: it rebalances rather than broadly suppresses immunity.

Clinically, VIP is the cornerstone of the final stage of the Shoemaker protocol for Chronic Inflammatory Response Syndrome (CIRS), a multi-system illness typically triggered by exposure to water-damaged buildings and mould. Abnormally low VIP is a hallmark laboratory finding in CIRS, and Shoemaker has documented intranasal VIP use in over 10,000 patients. Its hormonal effects, including modulation of ACTH and cortisol rhythms and prolactin release, are also given as the reason it appears in complex chronic illness protocols in late-stage disease.

The positioning is sequential and gated. VIP is not started until the patient is in a mould-safe environment, MARCoNS has been treated and confirmed negative, and other protocol steps are complete. This is not a first-line addition to a stack.

Route note: the clinical protocols use intranasal compounded spray, and the nasal route is argued to bypass first-pass hepatic metabolism, reach the brain via the olfactory pathway, and mimic natural VIP distribution more closely than injection. This page covers the injectable research form, for which a reconstitution (10 mg vial in 2 mL) is established but no injectable dosing protocol; the subcutaneous schedules previously documented on this page are retained in the dosing notes.

VIP signals through the G protein-coupled receptors VPAC1 and VPAC2, activating adenylate cyclase and raising intracellular cAMP. cAMP activates protein kinase A and the transcription factor CREB (cAMP response element-binding protein), altering gene expression, which is why VIP produces durable changes in immune function, inflammation, and repair rather than transient effects.

Immunomodulation. VIP reduces TNF-alpha, IL-6, and IL-12, increases IL-10, downregulates Th17 responses, and promotes regulatory T cell development. It also regulates Th1/Th2/Th17 balance, downregulates overactive macrophages and T cells, promotes immune tolerance, and protects endothelial and epithelial barriers. Delgado et al. (2004) reviews this dual pro-inflammatory suppression and anti-inflammatory upregulation, and Gonzalez-Rey et al. (2006) shows VIP generating tolerogenic dendritic cells that induce CD4 and CD8 regulatory T cells.

Vascular. Smooth muscle relaxation and vasodilation, reduced pulmonary artery pressure (the basis for its study in pulmonary arterial hypertension), improved tissue perfusion, reduced platelet aggregation, enhanced microcirculation, and VEGF stimulation for angiogenesis.

Neuroendocrine. Circadian regulation via the suprachiasmatic nucleus; modulation of pituitary release of growth hormone, prolactin, and luteinising hormone; modulation of ACTH and cortisol rhythms; regulation of pancreatic insulin and glucagon; neurotransmitter activity affecting cognition and mood; neuroprotection against oxidative stress and support for myelin integrity.

Gastrointestinal. Intestinal epithelial health and barrier integrity, regulation of gastric acid secretion and colonic water and ion absorption, increased intestinal blood flow, smooth muscle relaxation, and antimicrobial activity against certain pathogens.

CIRS mechanism. The chronic inflammatory cascade suppresses VIP production, reducing anti-inflammatory signalling and allowing inflammation to persist. Exogenous VIP reintroduces the missing signal; Ryan and Shoemaker (2016) documented expression changes in over 700 genes related to metabolism, inflammation, and immune function following treatment.

CIRS. Cornerstone of the final Shoemaker protocol stage. Shoemaker et al. (2013) documented reductions in C4a, TGF-beta 1, and MMP9, normalisation of testosterone and oestradiol, improved pulmonary artery pressure, improved pulmonary function and exercise tolerance, and a fall in mean symptom score from 12.9 to 3.3 (74 percent). Shoemaster et al. (2017) documented restoration of grey matter nuclear volume on MRI.

Immune modulation. Suppression of autoimmune-driven inflammation, downregulation of overactive macrophages and T cells, promotion of immune tolerance, without corticosteroid-like immunosuppression. Reduced joint inflammation and destruction in rheumatoid arthritis animal models; preserved intestinal barrier function in inflammatory bowel disease models; case reports of sarcoidosis improvement with inhaled VIP.

Pulmonary. Bronchodilation, reduced pulmonary inflammation, improved oxygen diffusion, alveolar epithelial protection. Petkov et al. (2003) showed reduced mean pulmonary artery pressure, increased cardiac output, and improved mixed venous oxygen saturation in primary pulmonary arterial hypertension.

Neurological. Enhanced cerebral blood flow, neuroprotection against oxidative stress, myelin support, neuroplasticity, circadian regulation affecting sleep and cognition, and objective grey matter restoration in CIRS.

Multiple chemical sensitivity. Low VIP correlates with chemical sensitivity; restoration is associated with marked decreases in reactions to environmental chemicals, consistent with VIP setting the immune threshold for inflammatory responses.

Gastrointestinal. Smooth muscle relaxation, increased intestinal blood flow, mucosal barrier integrity, reduced gut inflammation; essential for gut homeostasis.

Vascular. Vasodilation, improved endothelial function, reduced platelet aggregation, enhanced microcirculation.

Endocrine. Support for testosterone and oestrogen production, regulation of growth hormone release, influence on insulin sensitivity and prolactin, modulation of ACTH and cortisol rhythms, and circadian hormone balance. Hormone normalisation in CIRS is downstream of reduced inflammatory burden rather than a direct endocrine mechanism.

Off-label indications remain gated on normalised inflammatory markers, MARCoNS resolution, and eliminated mould or toxin exposure.

Shoemaker's published data show improvement within the first month and significant symptom reduction over 18 months of continuous use, in patients who had already completed the prior protocol steps: mould exposure addressed, MARCoNS treated, other steps complete.

Weeks 1 to 2. Users report improved energy and reduced brain fog in some cases; initial worsening in others, particularly where prerequisites were incomplete. Nasal irritation or mild congestion is common with intranasal use.

Weeks 2 to 4. More consistent symptom improvement, commonly fatigue reduction and cognitive gains. Improved sleep quality is reported, consistent with suprachiasmatic circadian regulation.

Months 1 to 6. Progressive improvement in inflammatory markers, normalisation of hormone levels, improvement in multiple chemical sensitivity, and grey matter restoration on imaging after several months.

After cessation. VIP levels may decline again if inflammatory triggers persist. Some patients require maintenance dosing; others discontinue after a full course.

Responder variability. At least one clinician reports approximately one-third of patients showing significant improvement, with the remainder responding neutrally or poorly; this is not well characterised in the published literature.

Evidence caveats: most CIRS data come from a single research group in open-label, uncontrolled designs (n = 20 in Shoemaker et al., 2013; n = 8 in Petkov et al., 2003), and the FDA has questioned whether sufficient safety data exist for chronic use. Premature initiation before prerequisites are met is the most frequently reported cause of non-response or worsening.

Route mismatch. The established practical protocols are intranasal. Studied doses: 50 mcg per spray four times daily in CIRS (Shoemaker et al., 2013); 200 mcg inhaled daily for 12 weeks, continuing to 24 weeks, in pulmonary arterial hypertension (Petkov et al., 2003). No published dose-finding studies compare VIP doses in humans. Shoemaker standard: 50 mcg per spray four times daily for 1 month, then 100 mcg per spray four times daily ongoing as needed, alternating nostrils. Clinical practice alternatives: 25 mcg starting dose titrated gradually for sensitive patients; 50 mcg twice daily maintenance; course length 1 to 6 months by response. The nasal route is argued to bypass first-pass hepatic metabolism, reach the CNS via the olfactory pathway, absorb rapidly, and mimic endogenous distribution better than injection. These figures are not rendered as protocol rows on an injectable page.

Reconstitution. 10 mg vial in 2 mL bacteriostatic water: 5 mg/mL, 50 mcg per insulin unit, 500 mcg per 10 units. This reconstitution is for research purposes.

Subcutaneous schedules previously documented here. 8-week cycle at 10 mg in 2.5 mL (40 mcg per unit): 100 mcg week 1, 150 mcg weeks 2 to 3, 200 mcg weeks 4 to 8, then 2 to 4 weeks washout; exact draws are 2.5, 3.75, and 5 units against rounded figures of 3, 4, and 5. 3-month cycle at 10 mg in 2 mL (50 mcg per unit): flat 200 mcg, exactly 4 units, then 1 month washout. Frequency 1 to 2 times daily, 5 days per week, morning or early afternoon to align with circadian and ACTH/cortisol regulation, fasted, with hydration stated as a requirement given vasodilation, hypotension, and diuresis on the adverse effect list. The second daily dose is not specified.

Prerequisites (Shoemaker). Mould-safe environment (ERMI less than 2 or HERTSMI-2 less than 11), passing Visual Contrast Sensitivity, MARCoNS treated and confirmed negative on retest, remaining protocol steps completed. Premature initiation while exposed to biotoxins or colonised is described as counterproductive and a likely explanation for non-response or worsening.

Storage. Lyophilised: minus 20 degrees Celsius long term, 2 to 8 degrees Celsius short term. Reconstituted: 2 to 8 degrees Celsius, use within 28 days, do not freeze, protect from light.

The clinical literature is small, largely single-group, and exclusively intranasal or inhaled.

Shoemaker et al. (2013), Health Journal — open-label trial of 50 mcg VIP nasal spray four times daily in 20 CIRS patients following water-damaged building exposure. Significant reductions in symptoms and inflammatory markers (C4a, TGF-beta 1, MMP9), improved pulmonary function and exercise tolerance, normalisation of testosterone and oestradiol, no significant adverse events. Mean symptom score fell from 12.9 to 3.3, a 74 percent reduction. Limitations: no placebo, open-label, single group.

Ryan and Shoemaker (2016), Medical Research Archives — RNA-seq transcriptomic analysis of VIP-treated CIRS patients showing changes in over 700 genes spanning metabolism, inflammation, and innate immunity, with a shift away from inflammatory profiles. No placebo control.

Shoemaker et al. (2017), Internal Medicine Review — before-and-after MRI demonstrating restoration of grey matter nuclear volume across multiple regions, correlated with symptom improvement. Patients served as their own controls.

Petkov et al. (2003), Journal of Clinical Investigation — open-label study of inhaled VIP in 8 patients with primary pulmonary arterial hypertension: reduced mean pulmonary artery pressure, increased cardiac output, improved mixed venous oxygen saturation. After 12 weeks of 200 mcg inhaled daily, physical capacity improved versus baseline (p < 0.01) and continued improving at 24 weeks (p < 0.01). No significant side effects.

Delgado et al. (2004), Pharmacological Reviews — mechanistic review: VPAC1/VPAC2-mediated cAMP–PKA–CREB signalling suppressing TNF-alpha, IL-6, and IL-12, raising IL-10, downregulating Th17, and promoting regulatory T cells.

Limitations: no randomised placebo-controlled trials in CIRS; CIRS remains a contested diagnosis; no human dose-finding studies; the FDA has questioned the adequacy of chronic-use safety data; independent replication is lacking. The injectable route addressed on this page has no clinical outcome data of its own — every figure above derives from nasal or inhaled delivery.