VIP

What is VIP and what does it do in the body?

VIP is a member of the secretin/glucagon hormone family and takes its name from its first noticed effect, its potent vessel-widening property. It acts through two receptors called VPAC1 and VPAC2; these receptors belong to the same class B G protein-coupled receptor family as the GLP-1 receptor. In the intestine it regulates gastric acid secretion, intestinal secretion, motility and immune responses in the mucosa; it has also been linked to blood sugar control, immune response and the daily biological rhythm. ^[1]

The secretory effects of VIP in the intestinal epithelium occur largely through the VPAC1 receptor. The effect of VIP excess in humans is also well known: rare tumors that secrete VIP (VIPoma) cause profuse watery diarrhea, low potassium and absence of stomach acid (achlorhydria) (Verner–Morrison or WDHA syndrome). Systemic intravenous VIP infusion has been seen to produce a drop in blood pressure in rats. ^[1]

The same review writes that VIP has been proposed as a possible therapeutic target for diarrhea, inflammatory bowel disease, diabetes, autoimmune diseases, neurodegenerative diseases, lung diseases, sarcoidosis and cancer, but that VIP-based drug development has not been “entirely successful” because rapid breakdown of the peptide limits bioavailability and delivery to the body. A significant part of the knowledge in these areas comes from animal and cell studies, such as the rhythm, immune and metabolic disorders seen in mice lacking the VIP gene. ^[1] Sales claims such as “balances the immune system” or “corrects autoimmune disease” therefore rest on areas not studied in humans.

For which use is aviptadil licensed?

According to the European Medicines Agency’s (EMA) 2022 list of nationally authorised products, the aviptadil/phentolamine mesilate combination is nationally licensed in Germany, Denmark, Finland, France, Norway and Sweden, and in Northern Ireland on behalf of the United Kingdom; this list covers only combination products. ^[2] The Scottish Medicines Consortium (SMC), Scotland’s medicines assessment body, assessed the product in 2017 for symptomatic treatment of erectile problems of neurogenic, vasculogenic, psychogenic or mixed cause in adult men, and limited its use to those who did not benefit from oral drugs (PDE5 inhibitors) and non-injection treatments. ^[3]

According to the SMC assessment, aviptadil is a neurotransmitter that regulates smooth muscle movement in the penis; phentolamine is a vessel-widening alpha-adrenergic receptor blocker, and the two together produce erection after stimulation. The main trial submitted to the SMC was an open-label, crossover-design comparison that excluded men with erectile problems of psychogenic cause: ^[3]

The SMC notes as limitations that the trial was open-label, that patient flow was incompletely reported, that separate results for the licensed dose were not given and that the study population was not selected by previous drug use; no priapism (prolonged erection) was reported in the trial. ^[3] This license is for an injectable drug used under specialist supervision and does not cover VIP products sold online.

What did the COVID-19 trials show?

During the pandemic, aviptadil was tried in critical COVID-19 patients on the assumption that it could protect the lung. Results differ according to trial design:

The TESICO authors report in detail the reactions during the first three days of infusion (days 0–2): low blood pressure occurred in 58.4% of the aviptadil group and 41.3% of the placebo group; diarrhea 39.8% vs 11.3%; facial flushing 14.7% vs 6.1%; tachycardia 9.5% vs 4.8%. The primary safety outcome, combining death, serious adverse event, organ failure, serious infection or grade 3–4 adverse event through day 5, was 63% in the aviptadil group and 56% in the placebo group (OR 1.40; 95% CI 0.94–2.08; p=0.10). The authors describe aviptadil as “an investigational drug with unproven clinical benefit.” ^[4]

In the second US trial the primary outcome was not significant; the survival difference the authors emphasize is a secondary outcome, and subgroup analyses were added to it. ^[5] The trial in Türkiye examined the inhaled form in milder patients and found a borderline significant difference in discharge; because it is a single, small trial, this result awaits confirmation. ^[6]

Sarcoidosis and lung diseases

In an open-label phase 2 trial in Germany, 20 patients with active sarcoidosis inhaled VIP by nebulizer for 4 weeks. In cells obtained from the lung lavage fluid, TNF-α production decreased and the number of regulatory T cells increased; the treatment was well tolerated. ^[7] The trial had no control group and the results were laboratory markers; clinical outcomes such as lung function or disease course were not primary measures. In the review, lung diseases and sarcoidosis are still counted among the “possible targets” for VIP. ^[1]

CIRS and the mold illness claim

CIRS is a multisystem disease definition associated with exposure to mold and bacterial products in water-damaged buildings. VIP nasal spray is the stage, in the stepwise treatment protocol of the physician who developed this definition, applied to patients who did not respond to the previous ten steps. The most cited study is an open-label trial in which 20 treatment-resistant patients were followed for 18 months while using VIP nasal spray. The authors report that symptoms and some blood markers fell to a level “not statistically different” from controls; however, the comparison was made not with a randomized placebo group in the same study but with historical values of 850 healthy people previously tested in the same clinic and with normal values. The study was conducted with patients of the clinic that developed the protocol. ^[8]

Even a review published in 2024 that evaluates the protocol favorably states, as its own limitation, that it is not systematic. The review places the three VIP studies it lists at the “non-experimental single study” level (level IV), below randomized trials: a 14-patient case series, a 20-patient open-label trial and another open-label trial; a case report that also includes VIP is at level VI. The two randomized trials in the review (8 and 13 people) were done not with VIP but with another drug, cholestyramine. The authors of the review are affiliated with clinics serving mold-related illness, and two declare that they act as expert witnesses in CIRS lawsuits. ^[9] The claim that “VIP treats mold illness” has therefore not been tested in a placebo-controlled trial.

Side effects and safety

The known physiological effects of VIP also explain its side effects. When given intravenously, low blood pressure, diarrhea, facial flushing and palpitations were significantly more common than with placebo. ^[4] With penile injection the most prominent difference is facial flushing (16% of injections). ^[3] VIPoma, the extreme example of VIP excess, shows that prolonged high VIP effect can cause fluid and potassium loss. ^[1]

Unlicensed nasal sprays or injectable “research peptide” products lack the checks of contents, purity and sterility that are mandatory for licensed drugs. For general risks: Peptide side effects.

What do regulators say?

• FDA (US): On the FDA’s list of substances nominated for compounding in pharmacies (updated May 14, 2026), “Vasoactive Intestinal Peptide” is in Category 1, that is, among “substances under evaluation.” This is not a drug approval; it only shows that whether the substance will be placed on the compounding list has not yet been decided. ^[10]
• Europe: In the EMA list, aviptadil is nationally licensed as a combination with phentolamine in six countries (five EU members, one Norway) and in Northern Ireland. ^[2]
• WADA: The 2026 Prohibited List does not name VIP or aviptadil. The S0 class prohibits at all times pharmacological substances that are not covered in any other section of the list and that no governmental health authority has approved for human therapeutic use. ^[11] Because aviptadil is licensed in some countries as a combination, how unlicensed VIP products stand under this definition is not separately explained in the list.

What is the status of VIP in Türkiye?

The legal status of peptides in general: Are peptides legal? The meaning of the “for research purposes” label: What does “research peptide” mean?

Evidence table: claim, population and limits

Limits of this guide

This page summarizes published evidence and official documents on VIP and aviptadil; it contains no individualized dose, preparation, administration method, course length or product source. Aviptadil’s documented licensed use is penile injection under specialist supervision; VIP products sold as nasal sprays or “research peptides” are not licensed for any use. The regulatory status may change; the information on this page is valid as of October 2026.