Aspirin Falls Short Against Blood Thinners After Joint Replacement, Trial Finds

The results come from the PEPPER trial, published in the New England Journal of Medicine, which tested three medicines against each other for preventing venous thromboembolism (VTE) — blood clots that form in the veins, most often in the legs or lungs — in patients recovering from hip or knee arthroplasty (joint replacement surgery).

The trial found that aspirin was not noninferior to rivaroxaban or warfarin for symptomatic VTE or death. In plain terms, it couldn’t be shown to be “no worse than” the other two drugs — a standard the trial was specifically designed to test.

But the findings cut both ways.

Warfarin and rivaroxaban were also not noninferior to aspirin on safety, meaning neither anticoagulant (blood-thinning medicine) could be shown to be as safe as aspirin in this patient group. Aspirin is generally considered to carry a lower risk of bleeding than stronger blood thinners.

The PEPPER trial results do not point to a straightforward winner. Clinicians will need to weigh the relative risk of clotting against the risk of bleeding for each individual patient — a judgement that has always sat at the heart of post-surgical blood clot prevention, and that these results make no simpler.

VTE after joint replacement is a recognised complication. Without preventive treatment, the NHS notes that patients undergoing hip or knee surgery face an elevated risk of deep vein thrombosis (DVT) — a clot in the leg — or pulmonary embolism (PE), where a clot travels to the lungs and can be life-threatening.

Patients due to have joint replacement surgery who have questions about their prescribed blood clot prevention should speak to their surgical team or GP rather than changing or stopping any medication. For urgent health concerns, NHS 111 is available around the clock.