A 28-amino-acid neuropeptide and vasodilator. Its synthetic form, aviptadil, has been studied clinically with mixed results, while an intranasal version is used off-protocol in the fringe CIRS community.
Reviewed for accuracy · Last reviewed July 8, 2026Vasoactive intestinal peptide (VIP) is a naturally occurring 28-amino-acid neuropeptide found throughout the nervous system. In the body it works as a neurotransmitter, a vasodilator, a secretagogue, and an immune regulator, signaling through the VPAC1, VPAC2, and PAC1 receptors. That endogenous biology is well characterized; what is far less settled is whether giving VIP as a drug helps any specific condition.
The synthetic form is called aviptadil, and its clinical record is mixed. A small phase 2 trial of inhaled aviptadil in COVID-19 pneumonia reported faster recovery, but the larger intravenous program (marketed as ZYESAMI) was unconvincing: the FDA declined an Emergency Use Authorization in 2021 and a major NIH-sponsored trial did not meet its primary endpoint. Separately, in the peptide community VIP is used intranasally as part of Ritchie Shoemaker's chronic inflammatory response syndrome (CIRS) protocol. That application is fringe and weakly evidenced: CIRS is not a mainstream-accepted diagnosis, and the intranasal VIP studies behind it are small, open-label, and uncontrolled. Nothing here is FDA-approved for these uses.
There is no approved dose. Community intranasal CIRS protocols commonly cite 50 mcg per spray several times daily, but this comes from a single small uncontrolled study and is not validated. Clinical inhaled aviptadil trials used different, protocol-specific dosing.
Read the full VIP (Vasoactive Intestinal Peptide) dosage guide →VIP is a vasodilator, so flushing, low blood pressure, and headache are the expected effects. The safety evidence for the community intranasal use is limited and comes from small, uncontrolled studies.
Read the full VIP (Vasoactive Intestinal Peptide) side effects guide →As a peptide, VIP/aviptadil is generally kept refrigerated and protected from light, and reconstituted or compounded preparations are handled per the compounding pharmacy's instructions. See the full storage & safety guide for general handling and disposal basics.
This page is an independent educational reference and is not medical advice, and does not indicate any approval status for any use. Talk to a doctor before starting any compound.