Drugs for Alzheimer’s disease – Harvard Health

There is no cure for Alzheimer’s disease, but medications can help control the disease. Currently, the main drugs used to treat Alzheimer’s are what are known as symptomatic therapies, meaning they relieve the symptoms but do not address the cause of the disease. These include cholinesterase inhibitors and memantine. A more recent entry into the field, lecanemab, may help slow disease progression. Here’s a look at how these drugs work.

Cholinesterase inhibitors

One of the ways Alzheimer’s damages the brain is by decreasing levels of a chemical messenger called acetylcholine, which helps with alertness, memory and thought processing. Cholinesterase inhibitors increase the amount of acetylcholine available to nerve cells by preventing its breakdown in the brain.

Three drugs in this category are FDA-approved: donepezil (Aricept), galantamine (generic), and rivastigmine (Exelon). They can be prescribed at any stage of Alzheimer’s, from mild to severe. The drugs are taken daily in pill form. Rivastigmine is also available as a skin patch.

These drugs can turn back the clock on memory loss, but only so far. “They can restore your memory as if it were six or 12 months ago, but drugs can’t slow the progression of the disease,” says Dr. Andrew Budson, chief of cognitive-behavioral neurology at the Harvard-affiliated VA Boston Healthcare System. “And you have to keep taking the drug to maintain that advantage.” People generally show the effects of the drug within one to two months.

Dr. Budson says most people do well with either cholinesterase inhibitor. “However, we have more experience with donepezil, so we usually try that first,” he says. “Galantamine is generally second-line.” The drugs are covered by Medicare and are well tolerated by most people. However, common side effects include upset stomach, nausea, vivid dreams, and loose stools.

Because rivastigmine comes in a patch, it is often used for people who cannot tolerate pills. Also, people with certain types of heart arrhythmias should not take cholinesterase inhibitors because they can slow the heart rate.

memantine

Another symptomatic drug approved for moderate to severe Alzheimer’s is memantine (Namenda). It works by modulating the effects of both glutamate and dopamine, two chemicals that send messages between nerve cells in the brain and are widely involved in brain functions, including memory.

Doctors usually prescribe memantine when a person with Alzheimer’s begins to have difficulty performing activities of daily living, such as dressing and bathing. “It’s prescribed to help slow the progression of symptoms, which might allow some people to maintain some daily functions a little longer than they would without the medication,” says Dr. Budson.

The medicine is taken as a pill or liquid once or twice a day. It may take up to three months, or even longer, to see any improvement. Common side effects include dizziness, headache, drowsiness, confusion, and agitation.

Lecanemab

This new drug, approved by the FDA in January 2023, works differently than other Alzheimer’s drugs by helping to slow the progression of the disease.

Lecanemab (Leqembi) is an immunotherapy that targets the beta-amyloid protein to slow the build-up of amyloid plaques in the brain. Plaques make it difficult for brain cells to communicate with each other, impeding memory and other mental functions. “The drug doesn’t prevent new plaque from forming, but slows down the rate at which it can build up,” says Dr. Budson.

The drug only works in people with early-stage Alzheimer’s, meaning they show mild cognitive impairment or mild dementia. “These are people who have problems with thinking and memory and struggle to complete complicated tasks like paying bills and buying groceries, but who have no problems with daily life,” says Dr. Budson.

A study published on January 5, 2023 a The New England Journal of Medicine looked at 1,795 people who had amyloid plaques in the brain (as confirmed by MRI) and mild memory problems. The researchers found that compared to people taking inactive treatment, those taking lecanemab for 18 months had a slower rate of cognitive decline (as measured by cognitive tests) and less amyloid in the brain.

Lecanemab is given every two weeks as a one-hour infusion. It is currently unknown whether a person should take it indefinitely. The main risks of the drug are brain swelling and brain bleeding, so people taking strong blood thinners are advised not to take lecanemab. Genetic testing for the Alzheimer’s risk factor gene is recommended for lecanemab candidates, as those with two copies of the gene may be three to 10 times more likely to experience side effects.

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