How do drugs for Alzheimer's disease work?

Here we explain the effects, within the brain and its nerve cells, of different types of cholinesterase inhibitors.

Cholinesterase inhibitors (donepezil, rivastigmine and galantamine)

In the brain of a person with Alzheimer’s disease, there are lower levels of a chemical called acetylcholine. Acetylcholine helps to send messages between certain nerve cells. In Alzheimer’s disease some of the nerve cells that use acetylcholine are also lost. Because of these changes in the brain, symptoms of Alzheimer’s disease get worse over time.

Donepezil, rivastigmine and galantamine all prevent an enzyme called acetylcholinesterase from breaking down acetylcholine. This means there is a higher concentration of acetylcholine in the brain, which leads to better communication between nerve cells. This may ease some symptoms of Alzheimer’s disease for a while.

All three cholinesterase inhibitors work in a similar way. However, one drug might be better for someone than another. For instance, a person may have fewer side effects from one drug.

NICE guidance on drug treatments

The National Institute for Health and Care Excellence (NICE) produces guidance on use of drugs in the NHS. NICE reviews the evidence and decides whether treatments represent good enough value for money to be available as part of standard NHS care. Drugs considered by NICE will also have been through the UK or European licensing process for new medicines. This means the medicine has been tested and met strict standards of safety, quality and effectiveness. The licence will be granted for treatment of a particular health condition (such as Alzheimer’s disease).

For the cholinesterase inhibitors, the NICE guidance (produced in 2011 and updated in 2016) suggests that the cheapest drug (currently donepezil) should generally be tried first.

Memantine

Memantine works differently from donepezil, rivastigmine and galantamine. Glutamate is another chemical that helps to send messages between nerve cells in the brain. However, when nerve cells are damaged by Alzheimer’s disease, too much glutamate is produced. This causes more damage to the nerve cells. Memantine protects nerve cells by blocking the effects of too much glutamate.

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