Alzheimer's disease (AD) is the most common form of dementia, accounting for about 70% of cases. The term dementia refers to a specific group of conditions. These conditions affect certain brain functions, such as memory, learning, and communication. There's currently no cure for AD. But medications can help improve symptoms or slow down how quickly AD progresses.

Donepezil (Aricept, Adlarity) is one common medication option for AD. Below, we'll discuss donepezil's mechanism of action, how long it takes to work, and how to tell if it's working.

What is donepezil?

Donepezil is part of a group of medications called cholinesterase inhibitors. It's a prescription medication approved for treating dementia related to AD. Donepezil comes in the following forms:

• Oral tablets: 5 mg, 10 mg, and 23 mg

• Oral disintegrating tablets (ODTs): 5 mg and 10 mg

• Skin patches: 5 mg/day and 10 mg/day

Donepezil tablets are taken daily. The skin patch, available as a brand-name product called Adlarity, is applied to the skin once a week.

Like all medications, donepezil can have side effects, such as nausea and diarrhea. But they're typically mild and go away on their own. However, severe side effects can rarely occur too. This includes bleeding in the stomach and a slowed heartbeat.

How does donepezil work?

Donepezil blocks the breakdown of acetylcholine (ACh). ACh is a naturally-occurring chemical in the body. It plays a key role in helping your nerves communicate. Having adequate amounts of ACh in the body helps maintain your ability to learn and remember things, among other functions.

Low ACh levels are one factor in the development of AD. Donepezil works by blocking acetylcholinesterase, an enzyme (protein) that breaks down ACh. Blocking acetylcholinesterase increases how much ACh remains in your brain. This helps your brain cells communicate more effectively, which can improve AD symptoms. However, donepezil also increases ACh in other areas of the body. This can lead to possible side effects.

Stopping the breakdown of ACh is donepezil's primary mechanism of action. But it may protect the brain in other ways too. This can include decreasing inflammation, improving blood flow, and preventing cell damage.

Historically, donepezil has been viewed as a medication that treats AD symptoms but doesn't slow down the progression of AD itself. However, some research shows that donepezil may slow down how quickly the brain declines in AD. It may also decrease the risk of death from AD.

Does donepezil start working immediately?

Donepezil doesn't start working immediately. But you may start to see improvement in your AD symptoms within a month of starting it. The exact timeframe can vary from person to person. But studies of donepezil often show that some symptom improvement occurs by 4 to 6 weeks. And symptoms may continue to improve over the next several months or even years. However, some research also shows that donepezil becomes less effective the longer you use it.

When starting treatment with oral donepezil, your prescriber will typically begin with a low donepezil dosage (5 mg). Depending on how you respond, they may slowly increase your dose to 10 mg or 23 mg over several months. The severity of your AD symptoms will help determine what dose is best for you.

For the patch form of donepezil, prescribers usually start treatment with the 5 mg/day patch. These patches are applied once a week. Prescribers typically wait at least 4 to 6 weeks before determining whether you should switch to the 10 mg/day patch. It's also possible to switch from oral donepezil to the patch. But you should work with your prescriber to find the best dose for you.

How do you know if donepezil is working?

If your AD symptoms improve, donepezil is likely working. This could mean you have less trouble completing your daily tasks and have an easier time remembering things. One way to monitor if your symptoms are improving is by using a symptom journal. If possible, try starting the journal before you start taking donepezil. This will make it easier to compare symptoms before and during treatment.

Your prescriber may also ask you to complete tests or surveys to monitor your AD symptoms. These tools assess memory, reasoning, and other brain functions affected by dementia. They can also help determine if an AD treatment, like donepezil, is working. Examples include the Alzheimer's Disease Assessment Scale - cognitive subscale (ADAS-cog), Severe Impairment Battery (SIB) test, and the Mini-Mental State Exam (MMSE).

Are there alternatives to donepezil for AD?

Yes, there are alternatives to donepezil for treating AD. It's also possible your prescriber will recommend combining several of the medications below to best treat AD.

Other cholinesterase inhibitors

Donepezil and other cholinesterase inhibitors, such as galantamine and rivastigmine (Exelon), are first choice options for treating AD symptoms. Rivastigmine is available as capsules and a patch. Galantamine is available as a tablet, extended-release capsule, and an oral solution. Patch and oral solution formulations may if you have difficulty swallowing tablets or capsules.

Overall, the cholinesterase inhibitors are considered similarly effective. But some research shows that galantamine and donepezil may be slightly more effective at improving brain-related symptoms. And oral rivastigmine may have a higher risk of side effects.

Memantine

Donepezil and cholinesterase inhibitors can be used alone. They can also be used in combination with another medication called memantine (Namenda). In fact, memantine and donepezil are combined in a combination pill called Namzaric.

Memantine is an N-methyl-D-aspartate (NMDA) receptor antagonist. It works differently from donepezil. Using these two medications together may be more effective than using either of them alone. This may be especially true in moderate to severe AD. Memantine is also used alone in some cases.

Anti-amyloid medications

Newer medications, which target the underlying mechanisms that cause AD, may also be prescribed. These include Leqembi (lecanemab) and Kisunla (donanemab). These injectable medications are administered in a hospital or infusion center.

These therapies work differently than donepezil. The main way they work is by targeting the formation of beta-amyloid plaques in the brain. The formation of these plaques leads to AD. So if they're not able to form, the progression of AD may slow down.

Medications for other AD symptoms

Other medications are available to treat certain symptoms that come along with AD. For example, Rexulti (brexpiprazole) treats agitation caused by AD. And Belsomra (suvorexant) treats insomnia caused by AD.