Which of the following agents is contraindicated in patients with a history of gastrointestinal bleeding?

The correct choice highlights aspirin as the antiplatelet agent that is contraindicated in patients with a history of gastrointestinal bleeding. Aspirin is known to inhibit platelet aggregation by irreversibly blocking cyclooxygenase-1 (COX-1) enzymes, which not only reduces thrombus formation but can also increase the risk of gastrointestinal irritation and bleeding. This side effect occurs due to the disruption of the gastric mucosal barrier and decreased prostaglandin production, leading to potential mucosal damage.

In patients who have a history of gastrointestinal bleeding, the risk of rebleeding is significantly heightened when aspirin is used, making it a less suitable option compared to other antiplatelet agents that may have a more favorable bleeding profile.

While clopidogrel and ticagrelor are also antiplatelet agents, they are generally considered to have a lower risk of gastrointestinal bleeding when compared to aspirin. Therefore, they may be safer alternatives in patients with a history of gastrointestinal issues, depending on individual patient risk factors and the clinical scenario.