Seizures can occur in people receiving donanemab (brand name Kisunla), but they appear as part of a broader brain reaction called ARIA, not as an isolated new side effect. According to the FDA prescribing information, serious ARIA events "including seizure and status epilepticus" can happen, though they are rare.
Donanemab is an intravenous antibody that clears amyloid plaque from the brain in early Alzheimer's disease. The FDA granted it traditional approval on July 2, 2024 for adults with mild cognitive impairment or mild dementia and confirmed amyloid pathology. Understanding where seizures fit in the risk picture helps patients and caregivers weigh the treatment realistically.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- What ARIA is, and why seizures belong to it
- How often does ARIA actually happen?
- How serious can it get?
- Who faces the highest risk?
- How the risk is monitored and reduced
- Frequently Asked Questions
What ARIA is, and why seizures belong to it
Seizures linked to donanemab do not arise on their own. They are one possible symptom of ARIA, short for amyloid-related imaging abnormalities—changes seen on brain MRI as the drug removes amyloid. ARIA comes in two forms. ARIA-E means fluid buildup, or edema, in brain tissue.
ARIA-H means small bleeds (microhemorrhages) or iron deposits on the brain surface, called superficial siderosis. Most ARIA causes no symptoms and is found only on scheduled MRI scans. When symptoms do appear, the Alzheimer's Association lists headache, confusion, dizziness, nausea, visual changes, gait trouble, focal neurologic deficits, and seizures. Seizure sits at the more serious end of that range.
How often does ARIA actually happen?
ARIA is common on imaging but usually silent. In donanemab trials, ARIA-E occurred in about 24% of treated patients versus 2% on placebo, per the FDA label. ARIA-H microhemorrhage reached 25% versus 11%, and superficial siderosis 15% versus 3%. The gap between imaging findings and felt symptoms is large.
Symptomatic ARIA-E affected roughly 3% of patients, and symptomatic ARIA-H under 1%. Seizure is a subset within that already small symptomatic group. That framing matters. A one-in-four MRI finding sounds alarming, but the odds of a serious event like seizure are far lower than the raw ARIA rate suggests.
How serious can it get?
aria can be fatal, and the trial record shows why the warning is not theoretical. In the Phase 3 TRAILBLAZER-ALZ 2 study of about 1,736 people, three donanemab-treated participants died from ARIA-related events, compared with one death on placebo, as reported in JAMA. Timing is a key detail.
Most ARIA appeared within the first three to six infusions, so the earliest weeks demand the closest attention. Status epilepticus—a prolonged, non-stopping seizure—is among the severe outcomes the label flags. These are rare events against a backdrop of frequent, harmless imaging changes. Still, seizure, especially a prolonged one, is a medical emergency that warrants immediate care.
Who faces the highest risk?
Genetics drive much of the danger. People who carry two copies of the APOE ε4 gene, known as homozygotes, have the highest risk of ARIA, including symptomatic cases. The FDA label recommends genotyping before treatment so patients understand their personal risk.
Vigilance is heaviest during the first 24 weeks. Because early infusions carry the most risk, clinicians watch this window most closely and counsel patients on warning signs. Watch for and report promptly:.
- New or worsening headache
- Sudden confusion or disorientation
- Dizziness or trouble walking
- Vision changes or nausea
- Any seizure activity
How the risk is monitored and reduced
MRI scans are the safety backbone. The FDA label requires a scan before starting and before the 2nd, 3rd, 4th, and 7th infusions to catch ARIA early. Based on severity, doctors pause or stop treatment.
The dosing approach has also changed. On July 8, 2025, the FDA approved a modified titration schedule that significantly lowered ARIA-E rates at 24 and 52 weeks while still clearing amyloid. In practice, that means the drug is now built up more gradually to reduce the early brain reaction that can lead to seizures. If you are considering donanemab, ask your clinician three concrete questions: What does my APOE genotype show? What is my MRI monitoring schedule? And what symptoms should trigger an urgent call or emergency visit?.
Frequently Asked Questions
Does donanemab commonly cause seizures?
No. Seizures are a rare, serious form of symptomatic ARIA. Most ARIA is silent and found only on MRI, and symptomatic cases affect a small minority of patients.
Can I lower my seizure and ARIA risk?
Genotyping identifies high-risk APOE ε4 homozygotes, the updated 2025 titration schedule reduces ARIA-E, and required MRI scans catch problems before they escalate.
What should I do if a seizure happens during treatment?
Treat it as an emergency and seek immediate care. A prolonged seizure, called status epilepticus, is among the severe outcomes the FDA label warns about.
