Final answer:
The nurse should monitor for gastrointestinal bleeding as an adverse reaction when a client is taking clopidogrel to prevent restenosis after stent placement, due to the drug's antiplatelet effects.
Step-by-step explanation:
The nurse should monitor the client who is taking clopidogrel for gastrointestinal bleeding. Clopidogrel is an antiplatelet medication that prevents platelets in the blood from clumping together to form clots. This medication is often prescribed to prevent restenosis, which is the re-narrowing of an artery after it has been treated with angioplasty and stenting. While gastrointestinal bleeding is not directly listed among the side effects in the provided reference, it is a well-known risk associated with antiplatelet drugs like clopidogrel since they affect the clotting process.