Combining Blood Thinners With Lecanemab or Donanemab: The Risk of Brain Bleeds Explained

In July 2023, the U.S. Food and Drug Administration granted full approval to lecanemab, sold under the brand name Leqembi®, for treating patients with mild cognitive impairment and early dementia caused by Alzheimer’s disease.

As the first fully FDA-approved drug designed to slow the progression of Alzheimer’s disease rather than just treat its symptoms, lecanemab represents a breakthrough for many who have experienced the devastating impact of dementia.

A year later, donanemab, sold under the brand name Kisunla™, became the second drug designed to slow the progression of Alzheimer’s to receive full FDA approval. This marked another noteworthy step in the fight against dementia.

But there’s also a risk associated with taking these medications that’s worth discussing: the risk of dangerous brain bleeds, which is higher in patients who are also taking blood-thinning medications. As a researcher at the Hinda and Arthur Marcus Institute for Aging Research and practicing cardiologist at Boston Medical Center aiming to improve the health of patients with atrial fibrillation, that risk stands out to me.

In this blog post, I’ll focus on considerations and challenges for patients with cardiovascular disease taking lecanemab or donanemab. 

What are lecanemab and donanemab? 

Both lecanemab and donanemab are part of a class of medications called anti-amyloid monoclonal antibodies. These antibodies work by clearing amyloid deposits from the brain. Amyloid plaques are a type of protein that builds up in the brains of those with Alzheimer’s disease, causing cell damage and disruption.

In clinical trials, lecanemab slowed the progression of dementia by 27%. Alvaro Pascual-Leone, MD, PhD, medical director of Hebrew SeniorLife’s Deanna and Sidney Wolk Center for Memory Health, wrote a blog post comparing this effect to slowing down a speeding car. If the rate of someone’s decline is comparable to a car going 70 miles per hour, lecanemab can slow that decline to 50 miles per hour — still fast, but at a slightly less dangerous speed. The results of studies with donanemab are similar.    

It’s important to note that lecanemab and donanemab are not appropriate for patients with advanced dementia or dementia due to causes other than Alzheimer’s disease. It is essential to rule out other causes of dementia with a comprehensive assessment before starting either medication.

Blood thinners and the risk of brain bleeds

During the clinical trials for lecanemab, researchers found that it can interact with blood thinners in a way that can be devastating for patients. Lecanemab is associated with an increased risk of cerebral macrohemorrhage, or large brain bleeds. Although these brain bleeds are rare, they can be severe — three patients in the clinical trial experienced fatal brain bleeds. Donanemab’s clinical trial saw similar results.

If you are taking a blood thinner such as Coumadin, Eliquis, or Xarelto, your risk of a dangerous brain bleed increases. While the FDA did not specifically warn against combining lecanemab or donanemab and blood thinners, the Alzheimer’s Association’s Therapeutics Work Group says those taking blood thinners shouldn’t be candidates for these anti-amyloid monoclonal antibodies because the risk outweighs the potential benefit.

It may seem straightforward: your doctor is unlikely to prescribe lecanemab or donanemab if you’re already on a blood thinner because the risk of brain bleeds would make it too risky. However, a few situations make the decision more complicated. 

What if a patient on lecanemab or donanemab has a heart attack or stroke? 

When someone has a heart attack or stroke, time is limited. In both critical situations, treatment involves giving patients powerful blood thinners intravenously. If they don’t receive those blood thinners, they risk severe or life-threatening health complications.

But if a patient is already on lecanemab or donanemab, treating them with a powerful blood thinner comes with the heightened prospect of causing a major brain bleed. It’s not an easy decision, and physicians should inform patients about this possibility before starting lecanemab or donanemab.

As more patients take lecanemab or donanemab, a growing body of data will become available to help patients and doctors make informed decisions about the dangers of treating versus not treating these medical emergencies with blood thinners. 

What if a patient on lecanemab or donanemab develops atrial fibrillation? 

Atrial fibrillation is an irregular heart rhythm that significantly increases your risk of stroke. AFib is common in older adults, with about 8-10% of patients 80 and older experiencing it. While some brush it off as not serious, that’s untrue — individuals with AFib have a five times greater increased risk of stroke, and strokes due to AFib tend to be more serious.  

Blood thinners are often prescribed to those with AFib to reduce their likelihood of having a stroke. So, what happens if you’re already taking lecanemab or donanemab for Alzheimer’s disease and develop AFib?

Should you stop taking lecanemab or donanemab and start taking blood thinners? Should you stay on lecanemab or donanemab and not start a blood thinner despite increased stroke risk? Should you take lecanemab or donanemab and blood thinners at the same time, despite a heightened possibility for a brain bleed?

Because data is still limited, and medical care and decision-making are deeply personal, there is no one-size-fits-all answer! Patients must speak with their care team about their options to make the best decision based on what matters most to them.

Quality care means keeping patients informed 

The decision to use lecanemab or donanemab, especially for those on blood thinners or at risk of cardiovascular events, is deeply personal. One patient’s top priority may be slowing down their dementia progression despite increased stroke risk. Another patient may be more concerned about stroke and decide that anti-amyloid monoclonal antibodies aren’t right for them.

Quality care means doctors across disciplines coming together, arming patients with the information we have now, and speaking to them compassionately so they feel empowered. If a medical emergency is the first time a patient or caregiver hears about the risk of brain bleeds associated with blood thinners and lecanemab or donanemab, that is devastating. When these conversations happen before a medical emergency limits options, patients can express their care preferences and make informed decisions in advance.

At the Hinda and Arthur Marcus Institute for Aging Research, we are writing a grant to research unanswered questions about anti-amyloid monoclonal antibodies and blood thinners and share even more data with patients. We aim to develop a decision aid that incorporates data from clinical trials and real-world use to help patients and doctors make decisions about lecanemab and donanemab. 

Worried about changes in memory? We’re here for you.

If you are interested in lecanemab or donanemab, you should talk with your primary care provider and see a dementia specialist for a detailed assessment and specific diagnosis. The Wolk Center for Memory Health has established policies and protocols to offer lecanemab to our patients. We are in the process of finalizing protocols to offer donanemab as well. 

The Wolk Center for Memory Health offers palliative consultations to explore goals of care before prescribing these medications, empowering patients and their loved ones to make the best-informed decisions based on their care preferences. We refer patients to specialty infusion centers to receive anti-amyloid monoclonal antibody infusions while offering ongoing monitoring and supportive care by our multidisciplinary care team. 

If you’d like to schedule a visit for a memory assessment, treatment, or family support, or you’re wondering if you’re a candidate for lecanemab or donanemab, we’d love to hear from you. Call us at 617-363-8600 or contact the Wolk Center online.

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