Why are warfarin and aspirin often considered relatively contraindicated when used together?

Combining them significantly increases the risk of dangerous bleeding, requiring a careful benefit-risk assessment.

Warfarin and aspirin are both agents that possess blood-thinning properties. When administered together, they significantly elevate the risk of dangerous, uncontrolled bleeding. This is categorized as a relative contraindication because, while the combination is generally avoided, a physician might determine that the immediate threat of a major clot is severe enough to justify the heightened risk of hemorrhage. In such instances, the treatment is only acceptable if the clinician closely monitors the patient to mitigate potential adverse events, turning the decision into a calculated risk assessment rather than a blanket refusal.