Which clinical finding is most concerning for a client who is prescribed octreotide?

A. Ileus: Octreotide can significantly slow gastrointestinal motility by inhibiting the secretion of gastrointestinal hormones and reducing peristalsis. Development of an ileus is a serious complication because it can lead to bowel obstruction, abdominal distention, pain, and potential ischemia, requiring immediate medical evaluation. B. Sinusitis: While sinusitis can occur as a nonspecific side effect, it is generally mild and not life-threatening. It does not directly relate to the pharmacologic effects of octreotide on the gastrointestinal or endocrine systems. C. Vomiting: Vomiting is a known but less severe gastrointestinal side effect of octreotide. Although uncomfortable, it is usually self-limiting and can be managed with supportive care or dose adjustment, unlike an ileus. D. Headache: Headaches are a common and generally mild adverse effect associated with octreotide. They are typically transient and do not indicate a serious pharmacologic complication or systemic risk requiring immediate intervention.