Octreotide is a medication that has physiologic effects that inhibit glucagon, insulin, splanchnic blood flow, and vasoactive peptides in the gastrointestinal tract. It has been used for treatment of watery diarrhea from tumors that secrete vasoactive intestinal peptides. Octreotide has been studied for management of chemotherapy- and radiation therapy-induced diarrhea. Octreotide is given by IV or subcutaneous injection. Prophylactic octreotide is the administration of the medication prior to symptoms in an effort to prevent development of diarrhea.