Which of the following agents is known to cause constipation?

Vincristine is an agent that is known to cause constipation as a side effect. This is primarily due to its mechanism of action, as it interferes with the microtubule formation in cells, which can affect gastrointestinal motility. The resulting decrease in peristalsis can lead to constipation, which is a frequent concern for patients receiving this chemotherapy drug.

While other chemotherapy agents can have a variety of side effects, they are not predominantly associated with constipation in the same manner as vincristine. For example, irinotecan is more commonly linked with diarrhea, particularly in its acute and delayed forms. Similarly, 5-FU and paclitaxel have different side effect profiles that do not prominently feature constipation. Therefore, vincristine stands out as the agent most directly associated with this particular gastrointestinal issue.