Vasoactive Intestinal Peptide (VIP): Function and Research
Vasoactive intestinal peptide (VIP) is a natural 28 amino acid neuropeptide that, per a 2013 review in Amino Acids, acts as a neurotransmitter, immune regulator, vasodilator and secretagogue. In plain words, it carries nerve signals, steers immune cells, widens blood vessels and makes cells release fluid. A rare tumor called a VIPoma makes too much of it. That causes watery diarrhea, low potassium and dehydration. As a drug named aviptadil, it did not significantly improve outcomes up to day 90 versus placebo in the TESICO trial (Lancet Respiratory Medicine, 2023), in people with COVID-19 respiratory failure. Inhaled, its effect in pulmonary hypertension was modest and short-lived.
Sources: Review: Delgado M et al. Vasoactive intestinal peptide: a neuropeptide with pleiotropic immune functions. Amino Acids, July 2013. PMID 22139413. Supports: 28 amino acid neuropeptide; four roles; released by neurons and immune cells; Review (StatPearls): Helbing A et al. VIPoma. StatPearls (NCBI Bookshelf), updated January 2025. PMID 29939520. Supports: rare neuroendocrine tumors; fasting-persistent watery diarrhea, hypokalemia, dehydration; life-threatening electrolyte problems; diagnosis at VIP above 250 pg/mL; Randomized, placebo-controlled trial: Brown SM et al. Intravenous aviptadil and remdesivir for treatment of COVID-19-associated hypoxaemic respiratory failure in the USA (TESICO): a randomised, placebo-controlled trial. Lancet Respiratory Medicine, September 2023. PMID 37348524. Supports: infusion schedule; no significant benefit to day 90; stopped for futility on 25 May 2022; safety outcome 63% vs 56%
Short answer
- What is VIP?
- A signal peptide your body makes. Both nerve cells and immune cells release it.
- What happens when VIP is too high?
- A VIPoma is a rare tumor that releases VIP. It causes watery diarrhea that goes on even when not eating. It can cause life-threatening salt and mineral problems. The StatPearls review (PMID 29939520) says diagnosis depends on a VIP level above 250 pg/mL.
- Does VIP work as a drug?
- Not shown so far. Breathed in, it had a small, short effect on blood pressure in the lungs (PMID 18978135). By vein in COVID-19, it did not clearly help in the TESICO trial (PMID 37348524).
Sources: Review: Delgado M et al. Vasoactive intestinal peptide: a neuropeptide with pleiotropic immune functions. Amino Acids, July 2013. PMID 22139413. Supports: 28 amino acid neuropeptide; four roles; released by neurons and immune cells; Review (StatPearls): Helbing A et al. VIPoma. StatPearls (NCBI Bookshelf), updated January 2025. PMID 29939520. Supports: rare neuroendocrine tumors; fasting-persistent watery diarrhea, hypokalemia, dehydration; life-threatening electrolyte problems; diagnosis at VIP above 250 pg/mL; Clinical study (20 patients, single dose): Leuchte HH et al. Inhalation of vasoactive intestinal peptide in pulmonary hypertension. European Respiratory Journal, November 2008. PMID 18978135. Supports: VIP (aviptadil) deficient; 20 patients; single inhaled 100 microg dose; modest, short-lived effect; Randomized, placebo-controlled trial: Brown SM et al. Intravenous aviptadil and remdesivir for treatment of COVID-19-associated hypoxaemic respiratory failure in the USA (TESICO): a randomised, placebo-controlled trial. Lancet Respiratory Medicine, September 2023. PMID 37348524. Supports: infusion schedule; no significant benefit to day 90; stopped for futility on 25 May 2022; safety outcome 63% vs 56%
What Is Vasoactive Intestinal Peptide?
Vasoactive intestinal peptide (VIP) is a 28 amino acid neuropeptide and neurotransmitter found widely in the nervous system, per a 2013 review in Amino Acids (PMID 22139413). A neuropeptide is a signal that nerve cells send.
The name gives two clues. "Vasoactive" means it acts on blood vessels. "Intestinal" points to the gut. But VIP is not only a gut signal. The same review says both neurons and immune cells release it.
VIP is a natural body signal, not a lab-made research compound. That sets it apart from many peptides people search for. When it is given as a drug in research, it goes by the name aviptadil.
Sources: Review: Delgado M et al. Vasoactive intestinal peptide: a neuropeptide with pleiotropic immune functions. Amino Acids, July 2013. PMID 22139413. Supports: 28 amino acid neuropeptide; four roles; released by neurons and immune cells; Clinical study (20 patients, single dose): Leuchte HH et al. Inhalation of vasoactive intestinal peptide in pulmonary hypertension. European Respiratory Journal, November 2008. PMID 18978135. Supports: VIP (aviptadil) deficient; 20 patients; single inhaled 100 microg dose; modest, short-lived effect
What Does VIP Do in the Body?
In the body, VIP acts as a neurotransmitter, an immune regulator, a vasodilator and a secretagogue, according to a 2013 review in Amino Acids (PMID 22139413). The review calls these effects pleiotropic. That means one signal with many effects.
| Role | What it means |
|---|---|
| Neurotransmitter | Carries signals between nerve cells |
| Immune regulator | Helps adjust how immune cells respond |
| Vasodilator | Widens blood vessels |
| Secretagogue | Triggers glands or cells to release fluid or other substances |
For other peptides studied for the gut, see peptides for gut health and peptides for inflammation.
What Happens When VIP Is Too High?
Very high VIP comes from a VIPoma, a rare tumor that causes watery diarrhea even when fasting, low potassium and dehydration, per the StatPearls VIPoma review (PMID 29939520). The review calls VIPomas rare neuroendocrine tumors. These are tumors of hormone-making cells. They release VIP with no control. This leads to a clear set of signs.
The signs
The review says the main signs of a VIPoma are:
- Watery diarrhea that goes on even when not eating
- Low potassium in the blood (hypokalemia)
- Dehydration
The blood test
The StatPearls review says a VIPoma diagnosis depends on a VIP level above 250 pg/mL. Doctors use that cut-off in a lab test. It is not something to judge on your own.
The review warns that VIPomas can cause life-threatening salt and mineral (electrolyte) problems. Bad watery diarrhea that will not stop, with signs of dehydration, needs a doctor fast.
VIP as a Drug: Aviptadil
Aviptadil is the name used for VIP when it is given as a medicine in research, and its two main human trials showed a modest, short-lived effect (2008, inhaled) and no significant benefit (2023 TESICO trial, by vein). Neither showed a strong benefit.
The idea of trying it in the lungs came from its role in widening blood vessels. A 2008 paper looked at pulmonary hypertension. That is high blood pressure in the lung arteries. The paper says VIP, which widens vessels, is deficient, meaning too low. The study then tested aviptadil, breathed in, in 20 patients.
What the Human Trials Found
Aviptadil's human trials found a modest, short-lived effect in pulmonary hypertension (European Respiratory Journal, 2008) and no significant benefit by day 90 in COVID-19 respiratory failure (TESICO, Lancet Respiratory Medicine, 2023). This table lines them up.
| Trial | Who | How it was given | Result |
|---|---|---|---|
| 2008 pulmonary hypertension study | 20 patients with high blood pressure in the lungs | Breathed in, one dose, during a heart test | Lung vessels widened a little, and not for long |
| TESICO, 2023 | COVID-19 patients with lung failure, USA (231 on aviptadil, 230 on placebo) | Into a vein, 12 hour infusion daily for 3 days | No clear gain by day 90; stopped early as unlikely to help |
Inhaled VIP in pulmonary hypertension
The 2008 study (PMID 18978135) had 20 patients with high blood pressure in the lungs. Nine had pulmonary arterial hypertension. Eight had it from lung disease. Three had it from old blood clots (chronic thromboembolic). Each breathed in one dose during right heart catheterisation. That is a test that measures pressure inside the heart and lungs. The authors (PMID 18978135) found the spray widened lung vessels only a little, and not for long.
As reported in that 2008 study:
Aviptadil, inhaled: a single 100 microg dose (100 micrograms)
Disclaimer: this is a research dose given once during a heart test. It is not label information and not a recommendation. Dose decisions belong with a licensed clinician.
Aviptadil by vein in COVID-19: the TESICO trial
TESICO was a randomised trial with a placebo group, done in the USA. The patients had COVID-19 and low oxygen from lung failure. In TESICO (PMID 37348524), aviptadil did not clearly improve how patients did up to day 90, compared with placebo. An independent safety board advised stopping the aviptadil trial on May 25, 2022. The reason was futility, meaning it was unlikely to show a benefit.
The TESICO paper reports this drip (infusion) plan:
12 hour infusion each day for 3 days: 600 pmol/kg on day 1, 1200 pmol/kg on day 2, 1800 pmol/kg on day 3
Disclaimer: these are target trial doses for very sick COVID-19 patients. They are not label information and not a recommendation. Dose decisions belong with a licensed clinician.
Safety was also tracked up to day 5. The main safety measure counted any of these: death, serious side effects, organ failure, serious infection, or grade 3 or 4 side effects. In TESICO, it happened in 146 of 231 patients (63%) on aviptadil. It happened in 129 of 230 (56%) on placebo. The paper says this gap was not statistically significant (p=0.10), so it may be chance.
Sources: Clinical study (20 patients, single dose): Leuchte HH et al. Inhalation of vasoactive intestinal peptide in pulmonary hypertension. European Respiratory Journal, November 2008. PMID 18978135. Supports: VIP (aviptadil) deficient; 20 patients; single inhaled 100 microg dose; modest, short-lived effect; Randomized, placebo-controlled trial: Brown SM et al. Intravenous aviptadil and remdesivir for treatment of COVID-19-associated hypoxaemic respiratory failure in the USA (TESICO): a randomised, placebo-controlled trial. Lancet Respiratory Medicine, September 2023. PMID 37348524. Supports: infusion schedule; no significant benefit to day 90; stopped for futility on 25 May 2022; safety outcome 63% vs 56%
Is VIP an Approved Drug?
VIP has no FDA label that we could find: an openFDA search in October 2026 returned no label for aviptadil or vasoactive intestinal peptide. The human data on this page come from research trials. They do not come from an approved product.
People also search for VIP nasal spray for chronic inflammatory response syndrome (CIRS). We searched PubMed for a human trial of nasal VIP for it. We found nothing that fit. We also found no label or official statement on who should not use VIP.
For how peptides are absorbed through the nose in general, see our peptide nasal spray guide. For general risks of unapproved peptides, see peptide side effects.
Common Questions
What is vasoactive intestinal peptide VIP?+
VIP is a natural peptide made of 28 amino acids. It is a neuropeptide, a signal used by nerve cells. It is found all through the nervous system. A 2013 review says it has four jobs. It carries nerve signals. It helps steer the immune system. It widens blood vessels. And it makes cells release fluid. Both nerve cells and immune cells release it.
What are the symptoms of high VIP levels?+
Very high VIP usually points to a VIPoma. That is a rare tumor that releases VIP without control. A StatPearls review lists the signs. There is watery diarrhea that goes on even when not eating. There is low potassium (hypokalemia) and dehydration. The review says it can cause life-threatening salt and mineral (electrolyte) problems.
What VIP level suggests a VIPoma?+
The StatPearls review says a VIPoma diagnosis depends on a VIP level above 250 pg/mL. A doctor does the test and makes the diagnosis.
What is aviptadil?+
Aviptadil is the name for VIP when it is given as a drug in research. It has been breathed in by people with high blood pressure in the lungs. It has also been given by vein to people with COVID-19 who could not breathe well.
Did aviptadil work for COVID-19?+
Not in the TESICO trial (PMID 37348524). Up to day 90, aviptadil did not do much better than placebo. The aviptadil part of the trial was stopped early in May 2022. The reason was futility, meaning it was unlikely to help.
Is VIP an approved drug?+
We found no FDA label for aviptadil or VIP in openFDA. The human data we found come from research trials. They do not come from an approved product.
Sources: Review: Delgado M et al. Vasoactive intestinal peptide: a neuropeptide with pleiotropic immune functions. Amino Acids, July 2013. PMID 22139413. Supports: 28 amino acid neuropeptide; four roles; released by neurons and immune cells; Review (StatPearls): Helbing A et al. VIPoma. StatPearls (NCBI Bookshelf), updated January 2025. PMID 29939520. Supports: rare neuroendocrine tumors; fasting-persistent watery diarrhea, hypokalemia, dehydration; life-threatening electrolyte problems; diagnosis at VIP above 250 pg/mL; Clinical study (20 patients, single dose): Leuchte HH et al. Inhalation of vasoactive intestinal peptide in pulmonary hypertension. European Respiratory Journal, November 2008. PMID 18978135. Supports: VIP (aviptadil) deficient; 20 patients; single inhaled 100 microg dose; modest, short-lived effect; Randomized, placebo-controlled trial: Brown SM et al. Intravenous aviptadil and remdesivir for treatment of COVID-19-associated hypoxaemic respiratory failure in the USA (TESICO): a randomised, placebo-controlled trial. Lancet Respiratory Medicine, September 2023. PMID 37348524. Supports: infusion schedule; no significant benefit to day 90; stopped for futility on 25 May 2022; safety outcome 63% vs 56%
Related reading
This guide is for educational purposes only and is not medical advice. It describes what published reviews and clinical trials report about vasoactive intestinal peptide and aviptadil. It is not an endorsement or an instruction to use any compound. We found no FDA-approved VIP product. Talk to a qualified healthcare professional before making any decision about your health.