Your Parent's Dementia Diagnosis Just Changed. Here Is What the New Drugs Actually Do.

The call usually comes on an ordinary Tuesday. A parent's neurologist has results. There's a new class of drug, the doctor says, and the patient might qualify. Twenty minutes of searching later, the screen is full of press releases that read like miracles and forum threads that read like warnings.

This article is the conversation worth having before the next appointment.

What These Drugs Are

Two anti-amyloid antibody drugs are now FDA-approved for early-stage Alzheimer's disease: lecanemab (brand name Leqembi) and donanemab (brand name Kisunla).3 Both work by the same basic mechanism. They're monoclonal antibodies, lab-engineered proteins designed to bind to amyloid-beta plaques in the brain and help the immune system clear them. Amyloid plaques are sticky protein deposits that accumulate between neurons. For decades, the dominant hypothesis in Alzheimer's research has held that this buildup is a primary driver of cognitive decline.

These drugs don't cure the disease. The damage already done stays done. What they do, based on Phase 3 clinical trial data, is slow the rate of cognitive decline by roughly 27% (lecanemab) to 35% (donanemab) over 18 months compared to placebo.1 In practical terms, a patient on donanemab might retain the ability to manage their own medications or remember a grandchild's name for several months longer than they would without treatment.

Several months. That's the scale we're talking about. Borrowed time, measured in seasons.

Whether that time is worth the cost and the logistical weight depends entirely on a family's specific situation. Here's what to weigh.

The Cost

Lecanemab costs approximately $26,500 per year. Donanemab runs about $32,000 per year, though Eli Lilly has indicated that treatment courses may be shorter, since patients who clear their amyloid can stop. Medicare Part B covers both drugs, but copays can still reach $6,600 annually for patients without supplemental coverage.5 For a parent with a Medigap plan or Medicare Advantage, out-of-pocket costs vary widely. Call the plan before the prescription.

The Logistics

This isn't a pill picked up at the pharmacy.

• Lecanemab. Biweekly intravenous infusions at an infusion center, each session about an hour plus monitoring time. An at-home injectable form is pending FDA approval as of early 2026 and would change the logistics considerably.
• Donanemab. A monthly IV infusion.
• Both drugs. Regular MRI monitoring, typically every few months, to watch for side effects.

The Risks

The side effect that matters most is ARIA: amyloid-related imaging abnormalities. That's a clinical term for brain swelling (ARIA-E) or microbleeds (ARIA-H) that show up on MRI scans. In clinical trials, ARIA occurred in 17% of lecanemab patients and roughly 30% of donanemab patients. Most cases were mild and resolved without symptoms. Some weren't. A small percentage of participants experienced headaches, confusion, dizziness, nausea, or visual disturbances. In rare cases, ARIA led to hospitalization. Three deaths in the donanemab trial were linked to ARIA complications.2

The risk is higher for patients who carry two copies of the APOE4 gene, a known genetic risk factor for Alzheimer's. Genetic testing (a blood draw) is now standard before prescribing either drug.6 For a patient who is APOE4 homozygous, the conversation with the neurologist needs to be longer and more specific.

Who Qualifies

Not everyone qualifies. Both drugs are approved only for early-stage Alzheimer's, meaning mild cognitive impairment or mild dementia with confirmed amyloid pathology. Confirmation requires either a PET scan or a cerebrospinal fluid test (lumbar puncture). For a parent in moderate or advanced stages, these drugs aren't indicated. Clinical trials excluded patients in later stages, so there's no efficacy data for them.

This is where families often hit the wall. The diagnosis comes, the drug exists, but the window for treatment may have already closed. Early detection matters more now than it did five years ago, precisely because these drugs only work in that early window.

What Is Coming Next

Beyond lecanemab and donanemab, the pipeline is active. BrightFocus Foundation's 2026 forecast notes that research is expanding beyond amyloid-only targets. Drugs addressing tau protein tangles and neuroinflammation are in Phase 2 trials. Others target synaptic repair. None are available yet. Planning around future drugs is premature, but knowing the field is moving matters for morale and for long-term care planning.

What to Do With This Information

Start with the parent's doctor, then weigh the logistics honestly.

1. Ask three specific questions. Does my parent meet the diagnostic criteria? What's their APOE4 status? Given overall health and the care situation, does the benefit-to-risk ratio favor treatment?
2. Map the logistics. Biweekly or monthly infusions require transportation, scheduling, and someone to drive home afterward, plus the MRI monitoring schedule and someone watching for ARIA symptoms between scans.
3. Have the harder conversation. What does "slowing decline" mean to the parent, not just the family? Several months of mild-stage function is worth the trade-offs for some families and not for others. Both answers are valid.
4. Look into financial assistance early. Eisai (lecanemab) and Eli Lilly (donanemab) offer patient assistance programs, and the Alzheimer's Association maintains an updated copay-assistance list. Do this before the first bill arrives.

The Hardest Part

The hardest part of these new drugs isn't the science. It's the hope management. A drug that slows decline by 27 to 35 percent matters. It's also a long way from a cure. Holding the real progress and the real limitations at the same time is the work.

Sources

1. van Dyck CH, et al. Lecanemab in Early Alzheimer's Disease. NEJM, 2023.
2. Sims JR, et al. Donanemab in Early Symptomatic Alzheimer's Disease. NEJM, 2023.
3. FDA. FDA Grants Traditional Approval to Leqembi for Treatment of Alzheimer's Disease.
4. Alzheimer's Association. Anti-Amyloid Treatments for Alzheimer's.
5. CMS. Medicare Coverage of Anti-Amyloid Antibodies for Alzheimer's Disease.
6. National Institute on Aging. Alzheimer's Disease Genetics Fact Sheet.

This article is for educational and informational purposes only. It does not constitute medical, legal, or financial advice. Always consult qualified professionals for guidance specific to your situation.

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