VIP is vasoactive intestinal peptide, a 28 amino acid neuropeptide whose physiology is unusually well characterized and whose clinical record is unusually thin. The gap between those two bodies of evidence is the whole story: decades of receptor and mechanism work sit alongside a handful of small, mostly inconclusive human trials and a compounded off-label market with no controlled data behind it. It is not an FDA-approved drug product in the United States.
VIP is a 28 amino acid neuropeptide signaling through the VPAC1 and VPAC2 receptors with a plasma half-life of one to two minutes, and it holds no FDA approval as a finished drug product, sitting instead in Category 1 of FDA's 503A bulk drug substances review.
The name is the most misleading thing about the molecule. VIP was isolated from porcine small intestine in 1970 during a search for a vasodilator, but the peptide turns up in cortical interneurons, the suprachiasmatic nucleus, autonomic ganglia, airway nerves, pancreatic islets, and lymphoid tissue. The theme running through all of those sites is the same: relaxation and secretion.
A VIPoma, a neuroendocrine tumor that floods the circulation with VIP, produces secretory diarrhea often exceeding three liters a day alongside hypokalemia, metabolic acidosis, and achlorhydria, which is the clearest natural demonstration of the peptide's physiologic reach.
Both receptors are class B G protein coupled receptors, and once VIP arrives both do essentially the same thing: raise cyclic AMP. The difficulty for anyone trying to build a drug on that system is that VIP binds VPAC1 and VPAC2 at roughly comparable nanomolar affinity, so a systemic dose engages lung, gut, vasculature, and immune tissue at the same moment.
VIP binds VPAC1 and VPAC2 with roughly comparable nanomolar affinity, so no systemic dose reaches one tissue without engaging vasculature, gut, lung, and immune compartments together, and the receptor-selective agonists developed to break that link have not reached broad clinical use.
Investigational status is routinely read as a softer form of approval, and it is not. Aviptadil has carried orphan drug designations for pulmonary arterial hypertension, sarcoidosis, and acute respiratory distress syndrome, designations that grant a development pathway and certain incentives without establishing that the agent is safe and effective for marketing. No finished VIP drug product has ever been approved in the United States.
VIP has never been approved by FDA as a finished drug product and sits in Category 1 rather than Category 2 of the agency's 503A bulk drug substances review, an interim evaluation posture that leaves a compounded prescription route open and can change if FDA later identifies safety risks or completes its rulemaking.
The mechanistic literature on VIP is large and the human literature is small, open label in most cases, and negative where it has been randomized. Every positive signal in the record so far arrived from a small uncontrolled study, and the controlled trial that followed did not reproduce it.
| Indication | Strongest design tested | Reported outcome |
|---|---|---|
| Pulmonary arterial hypertension | Randomized controlled trial, inhaled VIP | No meaningful hemodynamic benefit; earlier open-label gains not reproduced |
| Pulmonary sarcoidosis | Small phase 2, inhaled | Lower inflammatory markers in lavage fluid, no clinical improvement |
| COVID-19 respiratory failure | Randomized platform trial, intravenous aviptadil, 2023 | No significant benefit on the primary endpoint; no FDA authorization |
| Chronic inflammatory response syndrome | Case series and observational reports only | No randomized data and no independent replication |
Across pulmonary arterial hypertension, sarcoidosis, and COVID-19 respiratory failure, the randomized trials of inhaled and intravenous VIP have not met their primary endpoints, and the intranasal use rests on case series with no independent replication, so the record supports statements about biological plausibility rather than established treatment.
Chronic inflammatory response syndrome, abbreviated CIRS, is a framework describing a persistent multisystem inflammatory state attributed to biotoxin exposure, most often water damaged building mold. It is not recognized as a diagnosis by the American Academy of Allergy, Asthma and Immunology or the Centers for Disease Control and Prevention, both of which hold that the evidence does not support a distinct biotoxin driven syndrome of this kind. VIP enters late in that framework, and for a reason internal to it: proponents report the peptide as measurably low in affected patients.
Intranasal VIP is positioned as the final step of a sequential CIRS protocol on the basis of low measured VIP levels reported by the clinician group that developed the framework, a framework not recognized as a diagnosis by the American Academy of Allergy, Asthma and Immunology or the Centers for Disease Control and Prevention.
Route is not a detail with VIP, it is most of the story. A 28 amino acid peptide is digested in the gastrointestinal tract, so oral bioavailability is negligible and every studied use is parenteral, inhaled, or intranasal. Systemic exposure drives the dose-limiting effects, which makes the delivery route as decisive as the dose for anyone reading the safety record.
| Route | Regimen described in the literature | Exposure and monitoring |
|---|---|---|
| Intravenous | Slow infusion escalated over successive days, low tens of pmol/kg/min | Full systemic effect; continuous hemodynamic monitoring required |
| Inhaled or nebulized | Roughly 50 to 100 mcg per dose; 50 mcg in each of four daily inhalations in the pulmonary hypertension study | Concentrated in lung, yet flushing and hypotension still reported |
| Intranasal, compounded | Approximately 50 mcg per spray, several sprays daily, adjusted over months | Lowest systemic absorption, though not zero |
Every VIP regimen in the published record is intravenous, inhaled, or intranasal because the peptide has negligible oral bioavailability, and each was carried out under prescriber supervision in a study or clinical setting rather than as self-directed use.
Most of VIP's adverse effects are simply its pharmacology arriving in full. Vasodilation dominates the acute picture, and in the intravenous trials hypotension was dose limiting, with infusion rates titrated downward when pressure fell. The gastrointestinal effects run on the same mechanism that produces secretory diarrhea in VIPoma.
Hypotension, reflex tachycardia, flushing, headache, and secretory diarrhea are predictable pharmacologic effects of VIP rather than idiosyncratic reactions, and because no controlled long term safety data or post-marketing surveillance cover compounded and gray-market preparations, an absence of reported harm in that setting is not evidence of safety.
One number governs almost everything about how VIP can be used: a plasma half-life on the order of one to two minutes. Peptidases including dipeptidyl peptidase 4, neutral endopeptidase, and mast cell tryptase clear it, with substantial first-pass extraction in lung and liver on top of that. Any claim of a durable systemic effect from an intermittently administered dose has to rest on something other than persistent circulating peptide.
VIP's plasma half-life of one to two minutes means a continuous intravenous infusion and an intermittent intranasal spray are not testing the same exposure, so findings from one delivery route do not transfer to the other.
Educational use only. This article describes what the published scientific and clinical literature reports about VIP. It is not medical advice, and it does not recommend, prescribe, or tell anyone to use anything described here. The regulatory status shown at the top of this page reflects what the record showed on the date given there and can change. mdpep.com does not sell any substance described here, does not endorse human use of it, and does not direct anyone to obtain it.
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