VIP (Vasoactive Intestinal Peptide)

Vasoactive intestinal peptide (VIP) is an endogenous neuropeptide and hormone involved in smooth muscle relaxation, vasodilation, and regulation of secretory functions in the gut, lungs, and other tissues.

Therapeutic uses of VIP or VIP analogs are limited and experimental, though it is sometimes discussed in relation to conditions such as pulmonary or gastrointestinal disorders.

VIP acts on VPAC receptors, leading to increased cyclic AMP and downstream signaling that promotes smooth muscle relaxation, vasodilation, and changes in secretion.

These effects underpin both its physiological roles and potential therapeutic applications.

While VIP is an important endogenous molecule, direct therapeutic administration is relatively uncommon and largely investigational.

Catalog entries more often reflect research or early-stage therapeutic exploration rather than routine clinical use.

Potential risks include hypotension, flushing, tachycardia, and changes in gastrointestinal motility or secretions, depending on route and dose.

VIP has a short half-life and is prone to rapid degradation.

This information summarizes commonly discussed practices, particularly in environmental illness communities.

The form of VIP with clinical data behind it is aviptadil, a synthetic version prepared for hospital administration — given by intravenous infusion in the TESICO trial and by inhalation in a smaller Turkish trial. Research catalogs instead sell lyophilized VIP powder for reconstitution, and compounding pharmacies supply intranasal preparations used in chronic inflammatory response syndrome practice. Those three are different products with different exposure profiles, and only the first two appear in randomised trials.

Formulation matters more than usual here because VIP is degraded rapidly by enzymes, so stability and storage affect how much intact peptide survives to be delivered. Research has explored analogs and delivery systems designed to extend activity for exactly this reason. VIP is sometimes grouped with other vasoactive or pulmonary peptides in catalogs; no combination has been studied, and stacking a potent vasodilator with anything else that lowers blood pressure compounds an effect that already required intensive-care monitoring in trials.

Research on VIP and related analogs has explored potential roles in pulmonary, gastrointestinal, and inflammatory conditions. Results are preliminary and heterogeneous.

For deeper dives on this peptide, see:

• VIP (Vasoactive Intestinal Peptide) benefits and areas of interest
• VIP (Vasoactive Intestinal Peptide) side effects and safety context
• VIP (Vasoactive Intestinal Peptide) dosing concepts (educational)
• VIP (Vasoactive Intestinal Peptide) research and evidence overview

Is VIP or aviptadil approved by the FDA? No. Aviptadil, synthetic VIP, is investigational. Its most rigorous test — TESICO, part of the NIH ACTIV-3b programme — randomised 461 patients with COVID-19-associated hypoxaemic respiratory failure to intravenous aviptadil or placebo and found no benefit: the day-90 ordinal outcome gave an odds ratio of 1.11 (95% CI 0.80–1.55, p=0.54), mortality was 38% versus 36%, and the data and safety monitoring board stopped the trial for futility (Brown et al., Lancet Respir Med 2023).

Is there any positive human trial? One smaller one, by a different route. A multicenter, double-blind, placebo-controlled trial in Turkey gave inhaled aviptadil to 80 hospitalised COVID-19 pneumonia patients, reporting earlier discharge (7.8 ± 4.0 versus 10 ± 5.0 days, p=0.049), better breathing scores at day 7, greater CT improvement at day 28, and mortality of 5.1% versus 12.2% (Esendagli et al., Med Princ Pract 2025). It is one-sixth the size of TESICO, in less severely ill patients, and is best read as hypothesis-generating.

What does too much VIP do to a person? Medicine has a natural experiment for this. VIPoma, a rare neuroendocrine tumour that secretes VIP without regulation, produces watery diarrhoea, hypokalaemia and achlorhydria, with fluid replacement and electrolyte correction as first-line management (Karele, Presse Med 2024). It is the clearest available description of sustained VIP excess in humans.

Does intranasal VIP treat chronic inflammatory response syndrome or mould illness? No randomised controlled trial has evaluated intranasal VIP for those indications. The underlying immunology is genuine — VIP induces regulatory T cells and tolerogenic dendritic cells and has been effective in experimental autoimmune models, with limited human evidence in sarcoidosis (Souza-Moreira et al. 2012) — but detailed intranasal schedules come from clinical practice descriptions rather than from trials.

Why is aviptadil given by infusion instead of injection? Because VIP is cleared rapidly and lowers blood pressure. TESICO used daily 12-hour infusions for three days, escalating from 600 to 1,200 to 1,800 pmol/kg, in patients who were 94% in intensive care at baseline. A continuous infusion sustains a controlled concentration against fast degradation; a bolus of the same quantity would be a different and hemodynamically riskier event.