VIP

What is VIP?

Vasoactive Intestinal Peptide (VIP) is a 28-amino acid neuropeptide found throughout the body, particularly in the gut, brain, and immune system. Its synthetic form, aviptadil, has been tested in multiple RCTs for COVID-19-related respiratory failure and ARDS. VIP has also been investigated for pulmonary hypertension, autoimmune diseases (rheumatoid arthritis, lupus, Sjogren syndrome), and neurological disorders. It is used in the Shoemaker Protocol for CIRS, though published controlled trial data for that indication is limited.

What VIP Is Investigated For

Vasoactive Intestinal Peptide is investigated across COVID-19 acute respiratory distress syndrome, pulmonary hypertension, autoimmune diseases (rheumatoid arthritis, lupus, Sjogren syndrome, Graves' disease), chronic inflammatory response syndrome (CIRS), gut inflammation, and neurodegenerative disease. The strongest clinical data actually comes from inhaled VIP studies in pulmonary hypertension and from immunology research in rheumatoid arthritis, with mixed results from the multiple aviptadil RCTs in COVID-19 ARDS — the FDA declined Emergency Use Authorization for IV aviptadil in 2021, and the subsequent TESICO trial did not support clear efficacy. The honest caveats are substantial. VIP is not FDA-approved for any indication, its use in the Shoemaker CIRS protocol (the most common off-label context) rests on clinical-protocol rather than controlled-trial evidence — and the CIRS diagnostic framework itself remains contested in mainstream medicine. The mechanism is well-characterized (VPAC1/VPAC2 cAMP signaling, anti-inflammatory cytokine shifts, regulatory T-cell induction), but translating strong mechanism into proven therapies has been difficult, and VIP has real hemodynamic effects at pharmacologic doses — additive hypotension with antihypertensives, nitrates, or PDE5 inhibitors is a genuine concern.

History & Discovery

Vasoactive Intestinal Peptide was isolated in the early 1970s by Sami Said and Viktor Mutt at the Karolinska Institute in Stockholm, working from porcine intestinal extracts. The 28-amino-acid sequence was characterized and quickly recognized as a potent vasodilator, bronchodilator, and smooth-muscle relaxant, with broad distribution across the gut, lung, central and peripheral nervous systems, and immune compartments. Over the following decades VIP's biology expanded into circadian regulation via the suprachiasmatic nucleus, regulatory T-cell induction, and activity-dependent neuroprotection through the ADNP pathway. Despite its attractive pharmacology, VIP never reached routine clinical use as a drug — its short plasma half-life, broad receptor distribution, and hypotensive effect at systemic doses made development difficult. In the 2010s the synthetic VIP analog aviptadil, developed by Relief Therapeutics and partnered with NeuroRx in the US, was advanced for acute respiratory distress syndrome and pulmonary hypertension, and became a high-profile investigational therapy during COVID-19. The FDA declined an Emergency Use Authorization for intravenous aviptadil in COVID-19 in 2021, and subsequent randomized trials (including the TESICO trial) did not support clear efficacy. In parallel, a separate and contentious clinical community — built around Ritchie Shoemaker's CIRS framework for biotoxin- and mold-related illness — adopted intranasal VIP as a late-stage protocol step, and research-chemical suppliers began selling injectable and intranasal VIP for that and adjacent indications. The mainstream therapeutic status of VIP remains unresolved.

How It Works

VIP is thought to act as a natural anti-inflammatory messenger in the body. Preclinical and early clinical research suggests it may help calm overactive immune responses, protect nerve cells, and regulate gut function. Its mechanism via VPAC1/VPAC2 receptors is well-characterized, though translating this into proven therapies is still in progress.

VIP binds to VPAC1 and VPAC2 receptors, activating cAMP-dependent pathways that suppress pro-inflammatory cytokine production (TNF-α, IL-6, IL-12) while promoting anti-inflammatory cytokines (IL-10). It inhibits NF-κB activation, reduces oxidative stress, and promotes regulatory T-cell differentiation. In the lungs, VIP acts as a potent vasodilator and bronchodilator. In the nervous system, VIP acts as a neurotrophic factor and modulates synaptic plasticity via activity-dependent neuroprotective protein (ADNP).

Evidence Snapshot

Research Gaps & Open Questions

What the current literature has not yet settled about VIP:

• 01Rigorous clinical efficacy — VIP has strong mechanistic rationale across many conditions, but outside the (negative) aviptadil COVID-19 and ARDS trials, most therapeutic claims rest on small trials, case series, or preclinical data.
• 02CIRS as a defined indication — the Shoemaker framework for CIRS is not accepted in mainstream medicine, and no randomized controlled trial of VIP specifically for CIRS has been published.
• 03Intranasal delivery pharmacokinetics in humans — how much VIP reaches systemic circulation and CNS compartments from an intranasal dose, and with what variability, is not well characterized.
• 04Long-term safety of chronic VIP administration — most exposure data is acute (infusion trials); safety of 6+ month daily intranasal use is essentially uncharacterized in controlled trials.
• 05Responder phenotyping — anecdotally, VIP response is variable; predictors of response (receptor expression, baseline inflammatory state, comorbidities) have not been mapped.
• 06Route-comparative efficacy — whether intranasal, inhaled, subcutaneous, or IV VIP produce different clinical effects in comparable populations has not been formally studied.

Forms & Administration

VIP is available as a nasal spray (most common for CIRS), via inhalation (studied for pulmonary hypertension), subcutaneous injection, and intravenous infusion. Route depends on the target condition. All injectable peptides should only be administered under the guidance of a qualified healthcare provider. Never self-administer without clinician oversight.

Dosing & Protocols

The ranges below reflect protocols commonly discussed in the literature and by clinicians — not a prescription. Actual dosing for any individual should be determined by a qualified healthcare provider who knows the patient.

VIP is not FDA-approved for any indication in the United States. Aviptadil (synthetic VIP) remains investigational and did not receive Emergency Use Authorization for COVID-19. Any use should be under the direct supervision of a qualified healthcare provider who can evaluate individual risk factors.

Timeline of Effects

Common Questions

Who VIP Is NOT For

Drug & Supplement Interactions

Formal human drug-interaction studies for VIP are essentially absent; what follows is derived from VIP's pharmacology rather than from dedicated interaction work. The most predictable interactions involve hemodynamics. VIP is a potent vasodilator, so concurrent use with nitrates (nitroglycerin, isosorbide), phosphodiesterase-5 inhibitors (sildenafil, tadalafil), alpha-blockers, or other antihypertensives carries a theoretical risk of additive hypotension. Patients on blood-pressure-lowering regimens should be monitored if VIP is added, particularly in the early dosing period. VIP's immunomodulatory profile — suppression of TNF-α, IL-6, and IL-12, promotion of regulatory T cells — creates theoretical interactions with biologic immunosuppressants and with conventional immunosuppressants used in autoimmune disease and transplantation, though the magnitude is unknown at human dosing. Because VIP relaxes GI and airway smooth muscle, overlapping effects with bronchodilators and prokinetic or anti-diarrheal agents are conceivable but not characterized. Patients on any regular medication should disclose VIP use to their full care team.

Safety Profile

Legal Status

Regulatory status changes over time. Verify current local rules with a qualified professional.

Myths & Misconceptions