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James Douketis, MD, is a professor of medicine and the David Braley-Nancy Gordon Chair in Thromboembolic Disease at McMaster University.
Are there any drug interactions that the physician using direct oral anticoagulants (DOACs) should be aware of? In particular, should we advise patients to avoid nonsteroidal anti-inflammatory drugs (NSAIDs) or antiplatelet agents during treatment?
That’s also a very important question. One of the simple things we can do to minimize bleeding in patients who are receiving anticoagulant therapy is to avoid the use of drugs like antiplatelet drugs: aspirin, or nonsteroidal anti-inflammatory drugs (NSAIDs), because often those drugs are not necessary. And often we see that they are used in patients who have not had a recent stroke or heart attack. And if we can do that, then we can reduce the risk for bleeding almost by 50%. Now, of course, there will be patients who may require it because they have, for example, a coronary stent. But a lot of them do not require to be on aspirin or an NSAID.
The second thing we need to be aware of with the newer DOACs is that there are in fact important drug interactions, which may affect the efficacy and the safety of the anticoagulants, the DOACs. So, what do I mean by that? Well, there are drugs that can act as inducers and that can potentiate the effect of the anticoagulants. And these are drugs like antifungal agents, and these are drugs like antimicrobial agents, or like antiviral agents. An important one that is recent is the drug Paxlovid, which we use for patients with coronavirus disease 2019 (COVID-19) because the antiviral drug ritonavir can exacerbate and accentuate the effect of the anticoagulant.
On the other hand, there are other drugs that can reduce the anticoagulant effect of the DOACs, and I’m referring to anticonvulsant drugs like Tegretol (carbamazepine) or phenytoin, and they do so by inducing or suppressing the effect and leading to diminished levels of the DOACs, which can increase the risk for thrombosis.
So, be aware of certain classes of drugs that have drug interactions with DOACs, predominantly anticonvulsants, antifungals, antivirals, and certain antibacterial drugs.
