Probably the most commonly prescribed medications for Alzheimer’s dementia in Australia are cholinesterase inhibitors. They work by preventing the breakdown of acetylcholine, a chemical messenger important for learning and memory. In the brain of a person with Alzheimer’s disease, there are lower levels of acetylcholine, a chemical which usually helps to send messages between nerve cells. There are three cholinesterase inhibitors approved for use in Australia for mild to moderate dementia: donepezil (Aricept), rivastigmine (Exelon) and galantamine (Razadyne). All three are available in the tablet form; Exelon is also available as a transdermal (absorbed through the skin) patch.
Then there is Memantine (Namenda) which works by a different mechanism, which is approved for moderate to severe dementia. When nerve cells are damaged by Alzheimer’s disease, too much of a chemical called glutamate (that usually helps to send messages between nerve cells in the brain) is produced. This may cause more damage to the nerve cell. Memantine protects nerve cells by blocking the effects of too much glutamate.
What clinical trials have shown is that all these medications can offer some relief from symptoms of Alzheimer’s dementia for some people for a limited period of time. They do not cure the disease - there is no evidence that they can stop or reverse the process of nerve cell damage that causes the disease. They may cause in a slight improvement or stabilise the disease for a period of one or two years. This may help patients to think more clearly, function better in daily activities, and have improved quality of life for perhaps a year or two. Therefore, I see them as “stay home pills”. There is some evidence that they may also help with behavioural psychological symptoms of dementia.
A small number of patients started on cholinesterase inhibitors develop mild to moderate side effects. They are more common in the beginning of the treatment. The most common side effects are diarrhoea, nausea, vomiting and loss of appetite. Less frequent side effects include dizziness, syncope (fainting), slow heart rate or interference with heart rhythm, falls, agitation, nightmares, suicidal thoughts and hallucinations. Memantine has a difference side effect profile, and a small number of patients develop side effects such as dizziness, headache, tiredness, agitation and hallucinations.
A specialist, such as a geriatrician, neurologist or psychiatrist will usually be involved in this assessment and the initial prescription of these medications. People who meet certain conditions required by the Pharmaceutical Benefit Scheme are able to purchase the prescription at the subsidised rates set each year by the Australian government.