A large-scale comparison of direct oral anticoagulants (blood thinners) commonly prescribed for heart rhythm disorders has found the drug associated with the lowest risk of bleeding, in a new study led by UCL researchers.

In the newspaper published in Annals of Internal MedicineResearchers report that one of the two most common direct oral anticoagulants (DOACs), apixaban, offers the lowest risk of gastrointestinal bleeding with similar effects on stroke prevention and other side effects.

DOACs are used to prevent strokes in people with Atrial fibrillation— slowly or irregular heartbeat– a disease that affects more than 33 million people worldwide. They have recently become more common than warfarin, the previous standard treatment, because they do not require as much follow-up (which was especially important during the COVID-19 pandemic) and have a lower risk of side effects.

For the new study, researchers compared the effectiveness and risk of side effects for the four most common DOACs. They looked at data from more than 500,000 new DOAC users in the UK, France, Germany and the US, including 281,320 apixaban users, 61,008 dabigatran users, 12,722 edoxaban users and 172,176 rivaroxaban users.

They found that all four drugs were comparable in results ischemic strokecerebral hemorrhage and all-cause mortality, while they identified a difference in the risk of gastrointestinal bleeding, which is one of the most common and worrisome side effects of DOACs.

The study found that apixaban was associated with a lower risk of gastrointestinal bleeding, with 19-28% lower risks compared to each of the other three DOACs.

The researchers found that their findings held true when looking only at those over 80 chronic kidney diseasestwo groups that are often underrepresented in clinical trials.

Co-author Dr Wallis Lau (UCL School of Pharmacy) said: “Direct oral anticoagulants have been increasingly prescribed worldwide in recent years, but evidence comparing them head-to-head has been limited. Our results show that apixaban may be preferable to others thin the blood due to lower rates of gastrointestinal bleeding and similar rates of stroke, a finding that we hope will be supported by randomized controlled trials.

“As with all medications, the potential risks and benefits may vary between individuals, so consideration of the full range of outcomes and side effects will still be necessary for each individual patient.”