Understanding Contraindications for Anti-Amyloid Therapy (Lecanemab & Donanemab)
If you or your loved one is considering lecanemab or donanemab, it is crucial to know that not everyone with early Alzheimer's can take these medications. Certain medical conditions, other causes of cognitive decline, bleeding risks, and specific medications can disqualify someone. This article walks you through the key contraindications, what to discuss with your doctor, and how to prepare for a safe evaluation. You are not alone in navigating this — there are concrete steps you can take to understand eligibility and make informed decisions.
Key points
- Anti-amyloid therapies (lecanemab, donanemab) are only for people with early Alzheimer's disease confirmed by amyloid PET or CSF testing.
- Contraindications include other causes of cognitive decline, bleeding disorders, anticoagulant use, active immunologic conditions, and certain medications that affect cognition.
- ARIA (brain swelling or bleeding) is a known side effect; baseline and follow-up MRIs are required to monitor for it.
- A complete medication review is essential — include all prescription, OTC, and supplements.
- Never stop or change blood thinners or other medications without consulting the prescribing doctor.
- If you or your loved one is not a candidate, there are still effective symptomatic treatments (donepezil, memantine) and lifestyle interventions that can help.
Why Contraindications Matter for Anti-Amyloid Therapies
Lecanemab and donanemab are groundbreaking because they target the amyloid protein in the brain, which is a hallmark of Alzheimer's disease. However, these are immunologic medications — they work by triggering the immune system to clear amyloid plaques. Because of this, they carry specific risks, especially a side effect called ARIA (amyloid-related imaging abnormalities), which can involve brain swelling or small hemorrhages. Researchers designed the clinical trials to exclude people who had conditions that would increase their baseline risk of bleeding or complicate the interpretation of cognitive changes. This means that even if someone has early Alzheimer's and amyloid in the brain, they may still be disqualified if they have other medical or neurological issues that could confuse the picture or raise safety concerns.
The Core Contraindications: What Doctors Look For
The first major contraindication is having any other condition that is causing cognitive impairment. If a person's memory problems are due to something other than Alzheimer's — such as vascular dementia, Lewy body dementia, frontotemporal degeneration, a brain tumor, severe depression, or a metabolic issue — then the anti-amyloid drugs are not appropriate. The medications are designed to attack amyloid that is driving the disease, and if another condition is the primary cause, the drugs won't help and could even be harmful. Similarly, if someone has an active immunologic diagnosis (like multiple sclerosis, lupus, or rheumatoid arthritis) or is receiving immunotherapy for another condition, they are generally excluded because the immune system is already activated in a way that could increase ARIA risk.
Bleeding Risk and Anticoagulant Medications
Another critical contraindication is any condition that increases a person's tendency to bleed at baseline. This includes a history of bleeding disorders, recent major bleeding (such as a hemorrhagic stroke), or being on blood-thinning medications (anticoagulants) like warfarin, apixaban, rivaroxaban, or dabigatran. The concern is that ARIA involves bleeding in the brain, and if someone already has a higher bleeding risk, the combination could be dangerous. Even antiplatelet drugs like clopidogrel (Plavix) or aspirin in high doses may be a concern, though some people on low-dose aspirin were included in trials. Your doctor will need to review all medications — including over-the-counter supplements like fish oil, vitamin E, or ginkgo biloba — as these can also increase bleeding risk.
Other Medications That May Interact or Cause Confusion
Certain medications can worsen cognitive symptoms or mimic dementia, and their use may disqualify someone from anti-amyloid therapy. For example, anticholinergic drugs (often used for urinary incontinence, allergies, or depression) can cause confusion and memory problems. Benzodiazepines (like alprazolam, lorazepam, or diazepam) are also problematic because they can cause sedation, dizziness, and increased fall risk, and they can make it harder to assess whether the anti-amyloid drug is working. Atypical antipsychotics (like quetiapine or olanzapine) carry a black box warning for increased risk of death in older adults with dementia, and they are generally avoided unless absolutely necessary. The key is that your doctor will want to ensure that any cognitive changes are truly due to Alzheimer's and not made worse by other medications.
General caregiving information, not medical advice. Check medications and major care changes with your clinician.
Step-by-step
Schedule a comprehensive evaluation with a neurologist or memory specialist experienced in anti-amyloid therapy.
Confirm Alzheimer's disease as the cause of cognitive decline via a positive amyloid PET scan or cerebrospinal fluid test.
Compile a complete list of every medication and supplement with doses and frequency, and review with your doctor for bleeding risks, cognition-worsening drugs, and immunologic conditions.
Complete a baseline MRI to check for pre-existing microbleeds, aneurysms, or significant white matter disease, and learn the ARIA monitoring schedule and warning symptoms.
Reassess benefit with your doctor after 3–6 months on the full dose; if no clear improvement or continued decline, discuss stopping the medication.
What not to do
Don't assume an early Alzheimer's diagnosis automatically qualifies someone for lecanemab or donanemab.
Don't stop or change anticoagulant or antiplatelet medications without coordinating with the prescribing doctor.
Don't overlook other possible causes of cognitive decline, such as vascular dementia, Lewy body dementia, or frontotemporal degeneration.
Don't take over-the-counter supplements like fish oil, vitamin E, or ginkgo biloba, or assume routine medications are safe to combine with anti-amyloid therapy without disclosure.
Don't skip the baseline MRI or follow-up monitoring scans.
Don't rush into treatment without fully understanding the risks, monitoring burden, and time commitment.
Practical tools
Medication & Supplement Master List
A single written record of every prescription, over-the-counter drug, vitamin, and supplement with dose, frequency, and reason for each. Update it whenever anything changes and bring it to every appointment.
Amyloid Test Decision Guide
A side-by-side comparison of amyloid PET scans and cerebrospinal fluid testing, including what each involves, typical costs, insurance tips, and a note to tell imaging staff if you are claustrophobic.
Doctor Visit Question Guide
A printable list of key questions: 'What is the exact cause of my cognitive decline?', 'Do I have any conditions or medications that would disqualify me?', 'What is the plan for monitoring ARIA?', 'How will we know if the medication is working?', and 'What symptoms should send me to the emergency room?'
Daily Symptom & Behavior Log
A notebook or spreadsheet where a caregiver records new symptoms — headaches, dizziness, vision changes, nausea, confusion, falls, or behavior shifts — with date, time, and severity, to differentiate ARIA from disease progression.
ARIA Emergency Card
A wallet-sized or fridge-magnet card listing ARIA warning signs (sudden headache, confusion, blurred or double vision, nausea or vomiting, difficulty walking, seizures) and instructing the reader to call the doctor or go to the emergency room if any appear.
Discuss with your clinician
Ask your doctor: 'Based on my complete medical history and current medications, am I a candidate for lecanemab or donanemab? If not, what are the specific reasons?'
If you are on a blood thinner, ask: 'Is it safe to pause or switch my anticoagulant to consider anti-amyloid therapy? What are the risks of stopping?'
If you have an autoimmune condition, ask: 'Does my immunologic diagnosis disqualify me from these medications? Are there any exceptions?'
If you have had a stroke or brain bleed, ask: 'Does my history of stroke make me ineligible? Should I see a specialist in vascular dementia?'
Ask about ARIA: 'What is my personal risk of ARIA based on my age, genetics (APOE4 status), and brain MRI findings? How will we monitor for it?'
If you are taking benzodiazepines or anticholinergics, ask: 'Can these medications be safely tapered or replaced before starting anti-amyloid therapy?'
Related guides
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- Navigating Clinical Trial Recruitment and Making Informed Research Decisions