Is it safe to take aspirin and warfarin together?

The ultimate goal in medicine: protect the patient from stroke. Even a heart doctor has to admit the dominance of the human brain.

Always think about preventing stroke. It’s one of the worst outcomes that can happen to a person. Life as a ‘normal’ human requires a healthy brain. A stroke irreversibly kills off part of the brain. Stuff you take for granted can go away: swallowing, speaking, understanding language, sight, movement of a limb, not drooling, and the list goes on.

The most common cause of stroke is ischemic–meaning a blocked blood vessel leading to the brain or in the brain itself. A common cause of ischemic stroke is embolic–or when a clot breaks off from somewhere else and travels north to the brain, lodging in an artery.

Aside from living a healthy lifestyle from the get-go, one of the best ways to prevent these catastrophes is to use drugs that inhibit clotting. Aspirin and clopidogrel (and others now) inhibit platelets from sticking together. We call them antiplatelet drugs. Warfarin, dabigatran (Pradaxa), rivaroxaban (Xarelto) and apixaban (Eliquis) block parts of the coagulation cascade and we call them anticoagulants. (The term “blood-thinners” is also used for these drugs, but it’s not really accurate, because they do not change blood viscosity.)

The problem in giving these drugs—like any drugs—is the tradeoff. On the one hand, the benefit is prevention of clots and strokes, but on the other is the risk of bleeding. The key is finding the right balance, picking the right patient and then discussing risk-tolerance with the patient. Remember, we don’t use the word ‘need.’ We talk about balancing benefits and risks and then we share the decision.

It turns out, rightly I think, that most medical doctors lean heavily towards stroke prevention. They know how awful strokes can be. And this thinking has led to combining these two classes of drugs.

Intuitively, the combination makes sense. The oral anticoagulant (OAC) takes care of “red clot” (cardioembolic) that occurs in low-flow states like atrial fibrillation and venous thromboembolism, and the antiplatelet drug treats the “white clot” associated with atherosclerosis. Cover the bases. Protect the patient.

Call this the ‘more is better’ approach. But these days, as many of you know, the new movement favors a ‘less is more’ approach. I spent a couple of weeks looking into the matter of combining aspirin and another anticoagulant. I figured that since the combination was so commonly used, there must be an extensive evidence base in support.

Here is what I have come up with. It was surprising.

You can read my survey over at A dangerous cocktail: Aspirin and anticoagulants