Objectives: Previous studies showed increased plasma motilin and substance P concentrations and accelerated motor function in the small bowel and colon in patients with carcinoid diarrhea. Octreotide is beneficial in patients with carcinoid syndrome. Our hypothesis was that octreotide inhibits accelerated motility and gut neuropeptides in carcinoid syndrome.
Methods: In 12 patients with metastatic carcinoid syndrome, we investigated the effect of octreotide 50 microg s.c. t.i.d (n = 6) or placebo (n = 6) on postprandial symptoms, GI transit, colonic motility, and circulating levels of selected circulating peptides and amines.
Results: Octreotide reduced postprandial flushing (p = 0.03) but not pain. Octreotide significantly retarded overall colonic transit and proximal colonic emptying (p < 0.05); it tended to prolong small bowel transit time (p = 0.13) and to reduce postprandial colonic tone (p = 0.08) compared with placebo. Octreotide also reduced circulating levels of peptide YY, neurotensin, vasoactive intestinal polypeptide, and substance P but had no effect on plasma motilin, neuropeptide Y, calcitonin gene-related peptide, or histamine after meal ingestion.
Conclusion: Octreotide ameliorates gut motor dysfunctions that characterize carcinoid diarrhea; the potential role of specific antagonism of serotonin, substance P, and vasoactive intestinal polypeptide alone or in combination with agents that inhibit their release in carcinoid diarrhea deserves further study.