VIP is a peptide messenger found in the gut, blood vessels and nervous system. Its research history asks how one signal can carry different meanings in different tissues.
VIP · Immune and neuropeptide signalling
The gut does more than digest. Its lining talks to nerves and to immune cells, and the same chemical messengers turn up in blood vessels, the lungs and the brain's daily clock. VIP is one of those messengers. Researchers study it to understand how a single signal is reused across systems. The evidence runs from mouse models to human trials in specific lung conditions.
Vasoactive intestinal peptide (VIP) is a 28-amino-acid peptide isolated from pig small intestine by Said and Mutt in 1970. The name records where it was found and its first observed effect, relaxing blood vessels and lowering blood pressure (Said and Mutt, 1970); it does not describe the full range of its biology. VIP is released by nerve fibres and immune cells and acts through two receptors, VPAC1 and VPAC2, cellular receivers found on gut lining, smooth muscle, immune cells and neurons.
Because the same signal is read by so many cell types, VIP is studied less as a single-purpose molecule than as an example of how the nervous, immune and vascular systems share a vocabulary. The synthetic form used in medicines and clinical trials is called aviptadil.
Animal and cell work has examined the gut lining. In mice infected with Citrobacter rodentium, a bacterium that damages the intestinal barrier, VIP treatment reduced epithelial damage and prevented the loss of tight-junction proteins that hold lining cells together, with the same protective effect in a human cell line (Conlin et al., 2009). Separately, mice lacking VIP or its VPAC2 receptor lost the daily synchrony among neurons of the brain's master clock, showing VIP's role in coordinating circadian rhythm (Aton et al., 2005).
Human trials have used aviptadil in lung conditions. In 20 patients with pulmonary hypertension, raised pressure in the lung circulation, a single inhaled dose produced a small, temporary and selective fall in pulmonary vascular resistance (Leuchte et al., 2008). The far larger TESICO trial randomised 471 hospitalised adults with COVID-19 respiratory failure, almost all in intensive care, to intravenous aviptadil or placebo; among the 461 who received an infusion, no statistically significant difference was detected in clinical status at day 90 or in deaths, and the trial was stopped for futility.
One established medical use exists: aviptadil combined with phentolamine (Invicorp) is licensed in the United Kingdom as an intracavernosal injection for erectile dysfunction of neurogenic, vasculogenic, psychogenic or mixed cause (SMC, 2017).
VIP is broken down within minutes in blood, so route and formulation decide what any study is actually testing; an inhaled, intravenous or local injection result does not transfer to another route. The gut-barrier and circadian findings are in mice and cells and have not been tested as treatments in people. The human trials answer narrow questions in lung disease and, in the licensed product, in erectile dysfunction; TESICO did not detect a benefit in its setting. No clinical study has examined VIP together with any other compound in this catalogue, and the exact specification of the material offered here, including salt form, was not established for this note.
No Australian registration for VIP or aviptadil as a medicine was identified, and the Australian scheduling position for this specific product has not been confirmed. Overseas, aviptadil with phentolamine (Invicorp) is licensed in the United Kingdom for erectile dysfunction by intracavernosal injection. The TESICO trial in the United States did not support its use in COVID-19 respiratory failure.
Sources and status checked 2026-09-22
VIP — sizes and pricing