rivaroxaban and aspirin

Pharmacodynamic interaction: rivaroxaban inhibits factor Xa, reducing thrombin generation, while aspirin irreversibly inhibits cyclooxygenase-1, decreasing thromboxane A2 synthesis and platelet aggregation. The combined effects on the coagulation cascade and platelet function result in additive impairment of haemostasis.

Co-prescription significantly increases the risk of major bleeding, including gastrointestinal, intracranial, and retroperitoneal haemorrhage, compared with either drug alone. This can be life-threatening, particularly in patients with additional risk factors such as advanced age, renal impairment, or concurrent use of other antithrombotics.

Use with caution and only if the expected benefit outweighs the bleeding risk. If combined, prescribe the lowest effective doses, add gastroprotection with a proton pump inhibitor if appropriate, and monitor for signs of bleeding (e.g., haemoglobin, stool colour, mental status). Consider alternative antithrombotic strategies or shorter duration of combination therapy where possible.

The interaction is well documented in clinical trials and professional guidelines; however, specific recommendations vary by indication and regional protocols. It is supported by evidence from major cardiovascular outcome trials and bleeding risk assessments.