VIP (Vasoactive Intestinal Peptide)

Vasoactive intestinal peptide was first isolated from porcine duodenum in 1970 by Sami Said and Viktor Mutt. They initially identified it as a potent vasodilator, which gave it its name. Over the following decades, researchers discovered that VIP does far more than dilate blood vessels. It's a 28-amino-acid neuropeptide that functions as a neurotransmitter, immune regulator, and hormone across nearly every organ system. VIP's distribution in the body is remarkably broad. It's produced by neurons in the central and peripheral nervous system, immune cells, and endocrine cells in the gut. The highest concentrations are found in the gut (where it regulates motility and secretion), the lungs (where it controls bronchial tone), and the suprachiasmatic nucleus of the brain (where it helps set circadian rhythm). In clinical practice, VIP gained attention through Dr. Ritchie Shoemaker's work on Chronic Inflammatory Response Syndrome (CIRS). Shoemaker observed that patients with biotoxin illness (primarily from water-damaged buildings) had low VIP levels alongside elevated inflammatory markers like C4a, TGF-beta1, and MMP9. His treatment protocol uses intranasal VIP as the final step, after addressing other inflammatory pathways. His published case series showed that 30 days of intranasal VIP (50 mcg four times daily) normalized these markers in patients who had completed the preceding protocol steps. The immunology behind VIP is interesting. It shifts the immune system away from inflammatory Th1/Th17 responses and toward anti-inflammatory regulatory T-cell (Treg) activity. A 2013 review in Amino Acids (PMID: 22127915) detailed how VIP promotes Treg differentiation while simultaneously suppressing macrophage activation and dendritic cell maturation. This dual action, calming active inflammation while building tolerance, is what makes it useful in conditions driven by immune dysregulation rather than infection. The pulmonary applications have the strongest traditional clinical data. A 2003 pilot study in the Journal of Clinical Investigation (PMID: 12727921) tested inhaled VIP in 8 patients with primary pulmonary hypertension. Mean pulmonary artery pressure dropped by 13%, and cardiac output improved. The study was small but the results were consistent. VIP acts as a direct bronchodilator and reduces pulmonary vascular remodeling through anti-proliferative effects on smooth muscle cells. The main limitation of VIP therapy is its incredibly short plasma half-life: 1-2 minutes. Dipeptidyl peptidase IV (DPP-IV) chews through it almost immediately in the bloodstream. Intranasal delivery partly bypasses this problem by providing direct mucosal absorption and potential CNS access through the olfactory pathway. But it also means that systemic effects from intranasal dosing are modest. Storage requirements are strict. Compounded VIP nasal spray must be refrigerated at 2-8C. It's sensitive to heat and light. Patients should transport it in insulated containers and not leave it at room temperature for extended periods. Beyond-use dating is typically 30-60 days for compounded intranasal formulations. One practical concern: the diarrhea side effect is real. VIP stimulates intestinal chloride and water secretion, which is one of its normal physiological functions. At therapeutic doses, this can cause loose stools or frank diarrhea in some patients. Starting at a lower dose and titrating up over the first week helps.