Introduction:
Every so often, a clinical trial comes along that changes the way we think about treatment.
In atrial fibrillation, one of those trials was called AVERROES.
And it answered a very important question: if a patient with AF can’t take warfarin, is aspirin good enough — or is there something better?
The problem before AVERROES
“We’ve known for decades that atrial fibrillation increases the risk of stroke — strokes that are often severe and disabling.
Warfarin was the standard blood thinner, but many patients couldn’t take it — either because of bleeding risk, drug interactions, or difficulty with monitoring.
For those patients, the fallback was often aspirin.
But aspirin, while convenient, is much less effective at preventing stroke.”
The AVERROES trial design
“The AVERROES trial set out to test whether a new drug, apixaban — a direct oral anticoagulant — would be better than aspirin in patients with atrial fibrillation who were considered unsuitable for warfarin.
Over 5,500 patients were enrolled and randomised to apixaban or aspirin, then followed for strokes, systemic embolism, bleeding, and death.
The results
“The trial was stopped early — because apixaban was so much more effective.
- It reduced the risk of stroke and systemic embolism by about 55% compared with aspirin.
- And crucially, it did not increase major bleeding.
In other words, apixaban was both safer and more effective than aspirin.
- This was a landmark moment — showing that aspirin was simply not an adequate stroke-prevention strategy in AF.
Why it mattered:
The impact of AVERROES was huge.
It cemented the role of direct oral anticoagulants as the preferred treatment for AF patients at risk of stroke, even in those who couldn’t take warfarin.
And it essentially ended the era of aspirin as a serious option for stroke prevention in AF.
Today, guidelines are clear: aspirin should not be used for this purpose — and that’s thanks in large part to AVERROES.
Closing reflection:
So what’s the lesson from AVERROES?
That innovation, careful trial design, and the courage to test assumptions can completely reshape practice.
For patients with atrial fibrillation, it meant fewer strokes, fewer bleeds, and better outcomes.
And for doctors, it reminded us that we must always challenge the status quo when evidence points the way forward.
Here is a video I have done on this subject:
Excellent post—well-researched and genuinely informative, especially for a UK audience. I truly appreciate the focus on education and quality. Keep it up. We’re also sharing useful information and resources over at lysergamideworld.com for anyone interested.
The advice is flawed and possibly dangerous, The aspirin type is not stated in the body of the Averrose trial, but it is stated in the separate Protocol PDF document attached to the Averrose trial. You can find the type in seconds, here is how. 1, download the Protocol PDF, 2, open up the document, 3, on your keyboard press keys, control + F at the same time. There then appears a small box where you can type a word or phrase. 4, type the word enteric, then scroll down the open PDF file and if that word is listed anywhere in the PDF it will be highlighted. The actual Aspirin type used in the Averrose trial is the significantly less effective enteric coated. Do a search on the effect of both types. This is honest solid information, the Trial is funded in part by Big Pharma I believe.
Thank you Dr Gupta. I am on Apixaban and it works very well for me. I am 80 years old and active, yoga two or three times a week. Walking regularly, circle dancing and various other societies. Once again, thank you for good, honest, information we can understand.
The advice is flawed and possibly dangerous, The aspirin type is not stated in the body of the Averrose trial, but it is stated in the separate Protocol PDF document attached to the Averrose trial. You can find the type in seconds, here is how. 1, download the Protocol PDF, 2, open up the document, 3, on your keyboard press keys, control + F at the same time. There then appears a small box where you can type a word or phrase. 4, type the word enteric, then scroll down the open PDF file and if that word is listed anywhere in the PDF it will be highlighted. The actual Aspirin type used in the Averrose trial is the significantly less effective enteric coated. Do a search on the effect of both types. This is honest solid information, the Trial is funded in part by Big Pharma I believe.