VIP

Plain-English version: VIP is a small protein fragment (a "peptide") that your own body produces as a signaling molecule. It is 28 amino acids long and belongs to the same family as secretin and glucagon. Because your body already makes it, VIP is not a foreign chemical — a therapy made of VIP is essentially giving you more of a messenger you already have.

VIP was first isolated from pig small intestine in 1970 by Said and Mutt, who noticed its powerful ability to widen blood vessels and lower blood pressure — hence the name "Vasoactive Intestinal Peptide."^[1] Later research showed it is one of the most widely distributed neuropeptides in the body: it is found in the brain, spinal cord, autonomic nerves, gut, lungs, and immune cells.

Its jobs go far beyond widening blood vessels. VIP relaxes smooth muscle (in blood vessels and airways), regulates gland secretion, helps set the body's circadian clock, supports nerve survival, and — the property most therapies chase — calms inflammation by steering immune cells toward an anti-inflammatory state.^[2]

The credibility caveat, stated up front: VIP is not FDA-approved for any condition. Its synthetic twin, aviptadil (sold under research names ZYESAMI / RLF-100), was investigated for COVID-19 respiratory failure and even received FDA Fast Track and orphan-drug designations plus an emergency-use research allowance — but it was never approved, and its pivotal trial was stopped for futility.^[6] Today VIP is obtained through compounding pharmacies, most often as an intranasal spray for the off-label Shoemaker CIRS protocol. Compounded VIP is not an FDA-approved drug product. For the broader legal picture, see Are Peptides Legal?

Takeaway first: VIP is a two-receptor messenger. When it docks onto its receptors, it flips an internal "calm and relax" switch inside cells — quieting inflammation and widening blood vessels at the same time. Here is what the verified research actually shows.

1. VPAC1 and VPAC2 receptors — the two docking stations

VIP signals through two G-protein-coupled receptors (the same broad class many drugs target), called VPAC1 and VPAC2.^[2]

• VPAC1: heavily expressed on immune cells, and in the lungs, liver, and brain. This is the main route for VIP's anti-inflammatory and immune-calming effects.
• VPAC2: found on smooth muscle, in the central nervous system, and on immune tissue. It is involved in circadian (body-clock) regulation and in relaxing smooth muscle in blood vessels and airways.

2. Raising cAMP — the internal "calm" signal

When VIP activates either receptor, the cell ramps up a small internal messenger called cAMP (cyclic AMP). Rising cAMP is a well-established anti-inflammatory signal: it tells immune cells to dial down the production of pro-inflammatory chemicals and relaxes smooth muscle. This cAMP surge is the shared first step behind most of VIP's downstream effects.^[2]

3. Shifting the immune system from "attack" toward "tolerance"

In cell and animal studies, VIP nudges the immune system in several coordinated ways: it shifts helper T cells away from the pro-inflammatory Th1 pattern toward the calmer Th2 pattern, it encourages the formation of regulatory T cells (Tregs, the "peacekeeper" immune cells), and it tones down inflammatory macrophages and dendritic cells.^[2] This is the mechanistic reason VIP is studied as an immunomodulator rather than as a simple painkiller or steroid.

4. Widening blood vessels and relaxing airways

This is where VIP got its name. It is one of the body's most potent natural vasodilators — it relaxes the smooth muscle in vessel walls, which lowers pressure and improves blood flow, and it relaxes airway muscle (bronchodilation).^[1] This same property is a double-edged sword: it is useful in conditions like pulmonary hypertension, but it is also the source of VIP's main side effects (flushing, low blood pressure).

What we do NOT know

There is no established human pharmacokinetic profile for compounded intranasal VIP (how much actually reaches the bloodstream or brain, and for how long), and no human dose-response data for the CIRS use. The immune mechanisms above are real published findings — but the strongest ones come from cell cultures and animal models, and a clean mechanism in the lab does not guarantee a meaningful benefit in a person.

How to read this section: for each area we give the plain-English claim, the proposed mechanism, the population actually studied, the observed effect, and the limitation. VIP is unusual among research peptides in that it has real (if small) human data — but that data is mixed, and one large human trial was clearly negative. We flag the evidence level for each.

Anti-inflammatory / immune modulation (strongest human signal)

Claim: may calm overactive inflammation in the lungs and immune system. Mechanism: VPAC1/VPAC2 activation, rising cAMP, a Th1-to-Th2 shift, and more regulatory T cells. Population: 20 patients with sarcoidosis (an inflammatory lung disease) in an open-label Phase II study. Effect: four weeks of nebulized (inhaled-mist) VIP significantly reduced production of the inflammatory chemical TNF-alpha by cells collected from the lungs and increased regulatory T cells; it was described as safe and well tolerated.^[5] Limitation: small, open-label (no placebo group), and it measured biological markers rather than long-term clinical outcomes. This is the single strongest piece of human immunomodulation evidence for VIP, and it used an inhaled route, not a nasal spray.

Pulmonary (lung) hypertension

Claim: may lower dangerously high blood pressure in the lung arteries. Mechanism: potent vasodilation of the pulmonary blood vessels. Population: 8 patients with primary pulmonary hypertension in an open pilot study. Effect: inhaled VIP lowered mean pulmonary artery pressure and increased cardiac output and mixed-venous oxygen saturation (signs of better circulation), reportedly without side effects.^[4] Limitation: just 8 patients, no control group, acute (short-term) dosing. Describe this as promising and preliminary, not proof.

Autoimmune / inflammatory arthritis (animal evidence)

Claim: may reduce the severity of autoimmune inflammatory disease. Mechanism: combined anti-inflammatory (fewer inflammatory chemicals) and immunoregulatory (more tolerance) effects. Population: mice with collagen-induced arthritis (a standard model of rheumatoid arthritis). Effect: VIP significantly reduced both the incidence and severity of arthritis and prevented cartilage and bone destruction.^[3] Limitation: this is a mouse study — clearly animal, not human. It illustrates the mechanism but does not establish a human treatment.

CIRS / mold illness (the Shoemaker protocol use)

Claim: may normalize residual inflammatory markers in chronic inflammatory response syndrome. Mechanism: broad immune modulation and correction of a proposed VIP deficiency in affected patients. Population: patients in the Shoemaker CIRS/biotoxin-illness framework. Effect: intranasal VIP is used as the final step to correct persistent biomarker abnormalities (such as low MSH and elevated TGF-beta1) after other steps are done.^[7] Limitation — read carefully: this use rests on the Shoemaker protocol and practitioner literature, not on controlled trials of VIP. CIRS itself is not a mainstream diagnosis and does not appear in standard clinical guidelines. The foundational reference concerns the illness framework, not a placebo-controlled VIP trial.^[7]

The counterweight: a large NEGATIVE human trial

Honesty requires putting the biggest human trial front and center. In the TESICO trial, 461 patients with COVID-19-associated low-oxygen respiratory failure were randomized to intravenous aviptadil (synthetic VIP) or placebo. Aviptadil showed no benefit, and the aviptadil arm was stopped for futility.^[6] This is by far the largest and most rigorous controlled test of VIP-type therapy, and it was negative. It is a crucial reality check against optimistic framing: a strong mechanism and encouraging small studies did not translate into benefit in a large, properly controlled trial.

The honest bottom line on "benefits"

• The best human evidence is small and open-label (8 and 20 patients) and used inhaled/nebulized VIP, not the intranasal CIRS spray.
• The largest controlled trial was negative (TESICO, aviptadil, n=461).^[6]
• The most common real-world use (CIRS) is not trial-validated and is contested in mainstream medicine.
• Animal data are encouraging but preliminary — mechanism in mice does not guarantee benefit in people.

Read this first: there is no FDA-approved dose of VIP, because VIP is not an approved drug. Just as important, the doses used in the published human trials are different from the intranasal regimen used in the CIRS protocol. The trials used inhaled/nebulized VIP (pulmonary hypertension, sarcoidosis) or intravenous aviptadil (COVID-19); the popular "50 mcg per nostril, 4x daily" nasal-spray regimen comes from the Shoemaker protocol and practitioner literature, not from those peer-reviewed trials.^[4][5] We describe protocols here for completeness and harm reduction, not as medical guidance.

The single most important fact: a ~1-minute half-life

VIP is cleared from the blood extremely fast — roughly 1 minute by IV, and only modestly longer (a few minutes) after intranasal or subcutaneous absorption. This short half-life is the key practical driver of every dosing decision: it is why frequent dosing is used, why any single dose produces only a brief window of activity, and why inhaled/intranasal delivery (which puts VIP directly where it is meant to act) is preferred over trying to sustain blood levels.

Protocols by route (research- and protocol-derived, not FDA-approved)

Route	Dose	Frequency	Source of the protocol
Intranasal (most common today)	50 mcg per nostril (100 mcg total)	4x daily	Shoemaker CIRS protocol (practitioner-derived, not trial-validated)
Nebulized / inhaled	~100 mcg per dose	4x daily (studied over 4 weeks)	Sarcoidosis Phase II research[5]
Inhaled (acute)	Research dosing	Single/acute	Pulmonary hypertension pilot[4]
Intravenous (aviptadil)	Trial-defined infusion	Continuous, hospital only	TESICO COVID-19 trial[6]

Route logic in plain terms: for a lung target, inhaled/nebulized VIP delivers it straight to the airways. For the CIRS protocol, intranasal delivery is chosen for direct access to the nasal/CNS tissue and because a 4x-daily spray is far easier to self-administer than four daily injections. IV use belongs strictly to a hospital/clinical-trial setting.

The Shoemaker CIRS regimen in detail

In the Shoemaker protocol, intranasal VIP is used only as the final step, after every preceding step has normalized other markers.^[7] The standard regimen is 50 mcg in each nostril (100 mcg total), 4x daily, typically for about 30 days, then biomarker reassessment. The preceding steps generally include: removing the exposure (e.g., leaving a water-damaged building); a binder (cholestyramine or Welchol); treating MARCoNS (a resistant nasal Staph); normalizing visual contrast sensitivity; and normalizing markers such as anti-gliadin antibodies, androgens, ADH/osmolality, MMP-9, VEGF, C4a, TGF-beta1, and MSH — with VIP last. This is a contested protocol: CIRS is not in mainstream diagnostic guidelines, and the sequence comes from practitioner literature, not controlled trials.

Reconstitution math, with a worked example

If VIP is supplied as a lyophilized (freeze-dried) powder for a compounded injectable, it must be mixed with bacteriostatic water before use. The core formula is:

Concentration (mcg/mL) = vial amount (mcg) ÷ water added (mL)

Worked example: suppose a vial contains 1,000 mcg (1 mg) of VIP and you add 1 mL of bacteriostatic water. That gives 1,000 ÷ 1 = 1,000 mcg/mL. To draw a 100 mcg dose: 100 ÷ 1,000 = 0.10 mL, which is 10 units on a standard 100-unit insulin syringe. A 50 mcg dose is 0.05 mL, or 5 units. Note that most CIRS users receive VIP as a pre-mixed intranasal spray at a defined concentration per actuation, so they never reconstitute anything — the math above applies only to a compounded injectable powder. Use the peptide calculator and bacteriostatic water calculator to check volumes, and the reconstitution guide for a step-by-step walkthrough.

Cycle length and timing

• Typical CIRS course: about 30 days, then labs; some patients undergo multiple courses. In sarcoidosis research, nebulized VIP was studied over 4 weeks.^[5]
• Timing: the 4x-daily schedule spreads doses across waking hours because of the very short half-life; single daily dosing would only produce a brief effect.
• Blood pressure caution: because VIP is a strong vasodilator, checking blood pressure at baseline and hydrating before dosing is a sensible precaution (see Side Effects).

None of the above is a recommendation to self-administer an unapproved compound; it is a description of how the research and protocol doses are structured.

Straight talk: VIP is a peptide your body already makes, given back at near-physiological levels, so most of its side effects are predictable extensions of its normal biology — vasodilation (flushing, lower blood pressure) and stimulation of intestinal secretion (loose stools) — rather than off-target toxicity. In the small human studies, short-term inhaled/nebulized VIP was described as safe and well tolerated,^[4][5] and the large TESICO trial provides controlled safety data at scale for intravenous aviptadil.^[6] What does not exist is a large, long-term safety dataset for compounded intranasal use.

Reported and expected side effects

Effect	Frequency / route	Notes
Nasal congestion / irritation	Common (intranasal)	Mild, transient; vasodilation of the nasal lining
Facial flushing / warmth	Common	Vasodilation; usually lasts minutes after a dose
Low blood pressure (mild)	Occasional	Dose-dependent; more likely if volume-depleted or already hypotensive
Diarrhea / loose stools	Occasional	VIP stimulates intestinal water and electrolyte secretion
Headache	Occasional	Vasodilation-related, usually transient
Mild fast heart rate	Occasional	Reflex response to vasodilation
Bronchodilation	Mechanism, not adverse	VIP relaxes airway muscle — generally desirable
Allergic reaction	Rare	Discontinue immediately

No serious drug-related adverse events were consistently reported in the small published inhaled/short-term IV VIP studies at typical research doses, but those sample sizes were small.^[4][5]

Vasodilation and low blood pressure — the main practical caution

VIP is one of the body's most potent natural vasodilators, so blood-pressure effects are the issue to watch:

• Healthy, normotensive adults: usually just mild flushing and warmth, without a clinically important drop in blood pressure.
• Volume-depleted people (dehydration, recent diuretic use): can develop symptomatic low blood pressure.
• People on blood-pressure medication (calcium channel blockers, ACE inhibitors, ARBs, alpha blockers, nitrates): additive blood-pressure lowering.
• Cardiovascular instability (heart failure, recent heart attack, arrhythmia): use caution; excess vasodilation can worsen perfusion.

Practical rule: check blood pressure and pulse at baseline. If systolic blood pressure is under about 100 mmHg or you get lightheaded on standing, defer VIP until your volume status is adequate, and hydrate before dosing.

VIPoma: what extreme VIP excess looks like

Useful context: a VIPoma is a rare tumor that secretes massive, sustained amounts of VIP, causing severe watery diarrhea, low potassium, and dehydration (the WDHA / Verner-Morrison syndrome). Therapeutic dosing produces nothing close to that level of exposure — standard intranasal doses are far below it. But the syndrome is a reminder of the direction VIP pushes physiology at very high, sustained concentrations, which is exactly why protocols favor short-half-life intranasal or inhaled delivery over continuous infusion.

Who should avoid it, and key interactions

• Baseline low blood pressure or cardiovascular instability: avoid or use only under medical supervision.
• Volume depletion / dehydration: hydrate first.
• Severe heart failure, recent heart attack, or arrhythmia: defer.
• Active diarrheal illness: additive secretory effect.
• Pregnancy and breastfeeding: no controlled safety data — avoid.
• Active malignancy: VIP receptors are expressed on some tumors; discuss with oncology.
• Blood-pressure medications, PDE5 inhibitors (sildenafil, tadalafil), and alcohol: additive vasodilation — space dosing and monitor. Beta blockers may mask the fast heart rate that normally warns of a blood-pressure drop.

What to do if you have side effects

• Nasal irritation: alternate nostrils; saline rinse before dosing.
• Lightheadedness on standing: hydrate, dose lying down for the first few days, reduce dose, recheck blood pressure.
• Persistent diarrhea: reduce dose; ensure hydration and electrolytes, especially potassium.
• Palpitations or chest discomfort: discontinue and seek cardiac evaluation.
• Severe diarrhea with weakness or muscle cramps (a low-potassium pattern): discontinue and get electrolytes checked.
• Allergic reaction: discontinue immediately and seek emergency care.

For broader context, see Are Peptides Safe? and Peptide Side Effects.

Why this section matters: VIP is not an approved drug, so how you obtain it and how it is made matter enormously. In the U.S., compounded VIP is typically dispensed by a licensed compounding pharmacy with a prescription — a different (and generally more controlled) supply chain than the "research chemical" vials sold for many other peptides. But quality and concentration still vary between compounders, so knowing what to check is essential.

What a credible source should show

• Licensed compounding pharmacy: for intranasal or injectable VIP, a state-licensed compounding pharmacy filling a valid prescription is the standard route.
• Certificate of Analysis (COA): independent HPLC purity testing plus mass-spectrometry identity confirming the expected molecular weight, referenced to the specific lot.
• Correct appearance: VIP solutions are clear and colorless. Cloudy, discolored, or particulate-containing solutions should be discarded.
• Proper packaging and storage instructions: refrigerated intranasal spray, or lyophilized powder for injection with a beyond-use date.

Red flags

• No COA, or a COA from the seller rather than an independent lab
• Prices far below what a compounding pharmacy charges
• Vendors making explicit medical-cure claims (a sign of a non-compliant seller)
• Pre-mixed liquid with no stated concentration or beyond-use date

Legal and regulatory status (2026)

• Not FDA-approved for any indication.
• Aviptadil (synthetic VIP) was investigated but never approved: it received FDA Fast Track and orphan-drug designations and an emergency-use research allowance for COVID-19, but the pivotal TESICO trial stopped its arm for futility and it was not approved.^[6]
• Obtained off-label through compounding pharmacies, most commonly as an intranasal spray for the Shoemaker CIRS protocol. Compounded VIP is not an FDA-approved drug product.

Storage

• Intranasal spray: refrigerate at 2-8°C; use by the pharmacy's beyond-use date.
• Lyophilized powder: store frozen for long-term, or refrigerated short-term.
• Reconstituted injectable: refrigerate; avoid freeze-thaw cycles; protect from light.

See the full peptide storage guide, and for the complete legal picture read Are Peptides Legal?

VIP is often lumped in with "research peptides," but it plays a very different role from the popular recovery and growth compounds. It is not a healing or muscle peptide — it is an immune and vascular modulator. A few honest comparisons help place it:

• vs. BPC-157 and TB-500: those are studied for tissue repair (tendon, ligament, gut, muscle). VIP is studied for inflammation, immune tolerance, and vascular tone. Someone chasing injury recovery is usually looking at the Healing Stack, not VIP.
• vs. KPV: both have anti-inflammatory framing, but KPV (an alpha-MSH fragment) is a targeted anti-inflammatory studied for gut inflammation, while VIP is a broader neuroimmune and vascular modulator with a much stronger vasodilatory profile.
• Evidence base: ironically, VIP has more human data than most of these peptides — but that data cuts both ways, including a large negative trial. More studies is not the same as more proof of benefit.

If your interest is the CIRS/mold-illness pathway specifically, VIP is nearly always discussed as the tail end of a longer protocol rather than a standalone therapy — see the peptides for inflammation overview for where it fits.