There is no single best medication for Alzheimer’s disease. The most effective option depends on the stage of the disease, your genetic profile, and what you’re trying to achieve: slowing the underlying brain damage or managing day-to-day symptoms. Two categories of drugs now exist for Alzheimer’s, and they work in fundamentally different ways. Newer antibody infusions target the biological cause of the disease, while older medications help the brain compensate for damage that’s already occurred.
Two Types of Treatment, Two Different Goals
The first category includes cholinesterase inhibitors and an NMDA receptor blocker. These drugs have been available for decades. They don’t slow the progression of Alzheimer’s, but they can temporarily improve memory, attention, and the ability to carry out daily tasks by boosting chemical signaling in the brain. Think of them as helping the remaining healthy brain cells work harder.
The second category is anti-amyloid antibody therapy. These are infusion drugs approved in the last few years that actually clear amyloid plaques from the brain, the sticky protein deposits considered a hallmark of Alzheimer’s. By removing plaques, these treatments slow the rate of cognitive decline. They don’t reverse damage, but they meaningfully delay progression. They’re only approved for people in the earliest stages of the disease.
Anti-Amyloid Infusions: The Strongest Evidence for Slowing Decline
Two anti-amyloid drugs are currently on the market: lecanemab (Leqembi) and donanemab (Kisunla). A third, aducanumab (Aduhelm), was discontinued by its manufacturer, Biogen, and is no longer available. Both remaining drugs are given as intravenous infusions and are approved only for people with mild cognitive impairment or mild dementia due to Alzheimer’s.
Donanemab has shown the larger effect in clinical trials. In its Phase 3 study of over 1,700 patients, it slowed cognitive and functional decline by 40% compared to placebo over 76 weeks. For people with mild cognitive impairment specifically, the benefit was even greater: 60% slowing on a combined measure of cognition and daily function. That translated to roughly a 4.5 to 7.5 month delay in disease progression, depending on the measure used. Donanemab is infused every four weeks.
Lecanemab slowed clinical decline by 27% compared to placebo over 18 months in its pivotal trial of over 1,700 patients. It’s given as an infusion every two weeks. While the percentage is smaller than donanemab’s, direct head-to-head comparisons between the two drugs haven’t been conducted, so ranking one definitively above the other isn’t possible based on current data.
Safety Risks With Amyloid-Clearing Drugs
Both drugs carry a boxed warning for amyloid-related imaging abnormalities, or ARIA. This refers to temporary brain swelling and small spots of bleeding visible on MRI. Most cases are mild and resolve on their own, but serious episodes can occur. Lecanemab has the lower rate of brain swelling at about 12.6% of patients, while rates of small bleeding spots are similar across both drugs, around 17 to 20%. Infusion reactions (symptoms like chills, nausea, or flushing during treatment) are more common with lecanemab, affecting roughly 26% of patients.
Your genetic makeup matters here. People who carry two copies of a gene variant called ApoE ε4 face a significantly higher risk of ARIA, including serious cases. Genetic testing is required before starting either drug so you and your doctor can weigh the risks accurately.
Coverage and Access
Medicare covers both lecanemab and donanemab, but with a condition: your healthcare provider must enroll you in a qualifying study or registry and collect data on how well the drug works for you. This requirement exists because these treatments are still relatively new, and Medicare wants real-world evidence on their outcomes. You’ll need regular MRI scans to monitor for ARIA, and the infusions themselves require visits to a treatment center, which can be a practical barrier depending on where you live.
Cholinesterase Inhibitors for Mild to Moderate Stages
Three cholinesterase inhibitors are approved for Alzheimer’s: donepezil, galantamine, and rivastigmine. All three work by preventing the breakdown of acetylcholine, a brain chemical involved in memory and learning. As Alzheimer’s destroys the neurons that produce acetylcholine, these drugs help the remaining supply last longer.
A large meta-analysis of randomized trials lasting at least 52 weeks found all three are significantly better than placebo at preserving cognitive function. Rivastigmine showed the largest effect size on cognitive tests, followed by galantamine, then donepezil. However, donepezil is the most widely prescribed, largely because of its once-daily dosing and long track record. Rivastigmine is also available as a skin patch, which can reduce nausea, one of the most common side effects of this drug class.
In practice, the differences between these three drugs are modest enough that the choice often comes down to side effects and convenience. If one causes too much nausea or diarrhea, switching to another in the same class is a standard approach. These medications can delay cognitive impairment for at least a year, though they don’t change the ultimate course of the disease.
Memantine for Moderate to Severe Stages
Memantine (Namenda) is the only drug specifically approved for moderate to severe Alzheimer’s. It works differently from cholinesterase inhibitors. In Alzheimer’s, dying neurons release excess glutamate, a brain chemical that in high amounts damages neighboring cells. Memantine partially blocks the receptors that glutamate activates, protecting neurons from this toxic overflow without shutting down normal signaling.
Clinical trials in patients with moderate to severe Alzheimer’s found that memantine improved cognitive function, slowed the loss of daily living skills, and reduced the amount of caregiver assistance patients needed. In a 28-week trial of 252 patients, those taking memantine showed statistically significant improvements across cognitive, functional, and overall clinical measures compared to placebo. It’s generally well tolerated, with fewer gastrointestinal side effects than cholinesterase inhibitors.
Combining Medications
Many people with moderate to severe Alzheimer’s take both a cholinesterase inhibitor and memantine. The logic is straightforward: the two drugs work through completely different mechanisms. A 24-week trial of 403 patients already stable on donepezil found that adding memantine produced a small but statistically significant cognitive improvement over donepezil alone. However, pooled analyses across multiple studies suggest the real-world benefit of combination therapy over monotherapy is modest and of uncertain clinical significance. For patients with mild to moderate disease, adding memantine to a cholinesterase inhibitor showed no meaningful benefit.
Matching Treatment to Disease Stage
The practical reality is that the “best” medication shifts as the disease progresses. In the earliest stages, when mild cognitive impairment or mild dementia is confirmed and amyloid plaques are present on imaging, the anti-amyloid infusions offer the most meaningful benefit by slowing the disease itself. A cholinesterase inhibitor is typically started around this time as well to help manage symptoms.
As the disease moves into moderate territory, memantine enters the picture, often alongside whichever cholinesterase inhibitor is already in use. By the severe stage, the anti-amyloid drugs are no longer an option since they weren’t studied in and aren’t approved for advanced disease. Treatment focuses on memantine, continued cholinesterase inhibitor use if tolerated, and managing behavioral symptoms through other means.
None of these medications cure Alzheimer’s or restore lost function. The anti-amyloid therapies represent a genuine shift in treatment because they address the underlying disease process, but their effects are measured in months of delayed progression, not reversal. For many families, those months matter enormously.