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There is an immense amount of research taking place into new drug treatments for Alzheimer's disease and the other dementias.
The main compounds used are the cholinesterase inhibitors (also known as anti-cholinesterase drugs). Four have been licensed for use in many countries. These drugs work by reducing the breakdown of acetylcholine in the brain. Acetylcholine is a chemical substance that occurs naturally in the brain and enables nerve cells in the brain to pass messages to each other. Research has shown that many people with Alzheimer's disease have a reduced amount of acetylcholine, and it is thought that the loss of this chemical interferes with memory function.
The cholinesterase inhibitors include donepezil (Aricept®), galantamine (Reminyl® or Razadyne®), and rivastigmine (Exelon®). An earlier drug of this type was tacrine (Cognex®), which has mostly been superseded by the newer compounds because of its significant side effects. Side effects of these drugs may include diarrhoea, nausea, insomnia or vivid dreams, fatigue and loss of appetite.
It is important to realise that these drugs are not a cure, and can only stabilise some of the symptoms of early to mid stage Alzheimer's disease for a limited period of time.
NMDA receptor antagonist
More recently, a different type of drug has become available, which works to modify the function of the NMDA receptor. This is involved with the chemical transmitter glutamate, and research has suggested that too much glutamate is damaging or toxic to the nerve cell. Memantine (known as Ebixa®, Axura® or Namenda®) has been licensed in several countries for treatment of moderate to severe Alzheimer's disease. It is the first drug for people in the later stages of the disease. Although memantine can help with the symptoms, there is no evidence that it modifies the underlying pathology of the disease.
A number of other treatments, including vitamin E and omega-3 fatty acids, have shown some promising associations, but are not yet proven for routine use (and high doses of vitamin E can have negative effects). Nootropics, such as Ginkgo Biloba, are available in many countries. Ginkgo seems to improve cerebral blood flow, but consistent improved outcomes with it have not yet been clinically demonstrated.
Other kinds of drugs are sometimes useful for controlling some of the symptoms of dementia, such as aggression and delusions. In general, the use of sleeping pills or tranquillisers should be kept to a minimum if someone has dementia, as they can cause serious side effects including mobility problems and an increased risk of stroke, particularly when used over longer periods.