For more than 50 years, the gold standard drug to prevent stroke for patients with atrial fibrillation (Afib) has been warfarin (Coumadin). Now new guidelines for treating Afib bump that drug out of first place in favor of newer anticoagulants. If your doctor prescribed warfarin for your Afib, should you change medications? Facts to consider…
Warfarin works by blocking the effect of vitamin K, which is involved in the cascade of proteins called “clotting factors” that help blood to clot. Vitamin K levels fluctuate naturally, and consuming dietary sources—including leafy greens—also influences levels of the vitamin in the body. Since the effectiveness of warfarin depends on how much vitamin K is in the body, dosage of the drug has to be carefully monitored—too much can lead to bleeding, while too little doesn’t protect against stroke. So patients need to have their blood levels of warfarin checked often and, if necessary, the dosage adjusted. And they need to keep dietary sources of vitamin K at a steady level.
Nonvitamin K Anticoagulants
Alternative anticoagulants known as direct oral anticoagulants (DOACs) block clotting factors without depending on vitamin K. There’s no need for blood tests or dietary restrictions.
It would seem like a no-brainer to just switch patients over to these new medications. But without years of clinical trials attesting that they are safer and more effective than warfarin, doctors have been holding off. Now the American Heart Association has published updated guidelines for treating Afib that strongly recommend DOACs over warfarin, with some important qualifications. According to the available research, all four DOACs are about equally effective for Afib, but with some differences to consider…
• Dabigatran (Pradaxa). FDA-approved in 2010, the drug showed lower rates of stroke and systemic embolism compared with warfarin but had similar risks of bleeding. It can cause nausea or heartburn and is not recommended for patients with kidney problems. It is taken twice a day.
• Rivaroxaban (Xarelto). Approved in 2011, it’s taken only once a day. Another plus is that there are established dosing recommendations for patients with compromised kidney function, although it’s not advised for patients on dialysis or with severe renal dysfunction.
• Apixaban (Eliquis). Approved in 2012, it was shown to be superior to warfarin with regard to stroke and systemic embolism…and also caused less bleeding and resulted in lower mortality. While it, too, is not recommended for patients with severe kidney dysfunction, apixaban is the only DOAC recommended for patients with Afib on dialysis. It is taken twice a day.
• Edoxaban (Savaysa). Approved in 2015, edoxaban is unique among DOACs in that it can be used by patients who have some kidney damage and at a reduced dose by patients with more severe decreased kidney function. It is taken once daily and not recommended for patients on dialysis.
Important: The guidelines advise that patients with a heart valve problem stick with warfarin. There’s not enough evidence to say that DOACs are safer or more effective for this condition.
When first introduced, there was concern about life-threatening bleeding from DOACs because there was no reversal drug as there is for warfarin. However, research finds the risk of bleeding from DOACs to be lower than with warfarin. Also, idarucizumab (Praxbind) is now an approved antidote for dabigatran…Andexxa is approved for rivaroxaban and apixaban…and other reversal drugs are being developed. Still, bleeding is a serious concern when taking any anticoagulant. Signs to watch for include…
• Unexpected bleeding, such as from the gums, bladder/urine…or sudden swelling of the joints
• Unexplained bruising
• Bloody or black and tarry stool
DOACs are very expensive, so check with your insurer regarding coverage before talking to your doctor about changing your prescription.