Comparison of Apixaban and Aspirin in Preventing Stroke
Aspirin is a time-tested drug used as a painkiller and for fever. Besides, low-dose aspirin is used to prevent clotting of blood within the blood vessels. It brings about this action by preventing clumping of platelets.
Apixaban is a new drug currently undergoing clinical trials. It prevents clotting by a different mechanism. It acts by inhibiting the clotting factor Xa, an important protein in the clotting process.
The heart normally beats at a regular rate and rhythm. Atrial fibrillation is a condition where the upper chambers of the heart do not beat regularly. Thus, irregular signals pass through the lower chambers, resulting in irregular heartbeats. The process results in stagnation of blood within the heart and formation of blood clots. The clots can travel to the brain resulting in stroke. They may also travel through the blood (where they are referred to as emboli) and block the blood supply to important organs like heart and lungs.
A study compared the benefits of apixaban with aspirin in patients with or without previous stroke or transient ischemic attacks (TIAs) but unable to take anti-clotting medications like warfarin. Patients received either 5 mg of apixaban twice daily or 81 to 324 mg of aspirin per day. The patients were followed for a little over 1 year. They were monitored for side effects like bleeding.
In patients with a previous stroke or TIA, 10 events of stroke or embolism occurred in the total 390 patients receiving apixaban. In contrast, 33 events were noted in 374 patients receiving aspirin. In those without previous stroke or TIA, these events were 41 in the apixaban group, a total of 2417 patients compared to 80 in the aspirin group, a total of 2415 patients.
The incidence of bleeding between the aspirin and the apixaban groups was not significantly different.
Thus, the benefit of apixaban was much higher compared to aspirin in patients with atrial fibrillation regardless of whether the patient suffered from prior stroke or TIA.
However, further long term studies will be required to establish the role of apixaban in patients with atrial fibrillation. Also, the cost aspect will have to be kept in mind since aspirin is a very cheap drug whereas apixaban is likely to be expensive once it comes into the market.
1. Apixaban versus aspirin in patients with atrial fibrillation and previous stroke or transient ischemic attack: a predefined subgroup analysis from AVERROES, a randomised trial; Hans Christoph et al; The Lancet Neurology 2012