Treatment of Alzheimer's disease
As yet, there is no preventative or curative treatment for Alzheimer's disease.
Research has shown that the amount of a chemical called acetylcholine is diminishing in the brains of people with Alzheimer's disease. Acetylcholine is one of the many chemicals that nerve cells use to communicate and is a neurotransmitter that plays a critical role in memory and learning processes.
Donepezil, rivastigmine and galantamine have a common mode of action as all three drugs prevent an enzyme known as acetylcholinesterase from breaking down acetylcholine in the brain. However, rivastigmine inhibits both acteylcholinesterase and butyrylcholinesterase, the two enzymes that break down acetylcholine in the brain. Galantamine also appears to act on the nicotinic neuronal receptors in the brain, making them release more acetylcholine.
Increased concentrations of acetylcholine lead to improved communication between nerve cells involved in memory and learning, which may in turn temporarily improve or stabilise some of the key symptoms of Alzheimer's disease.
It is possible that one of these drugs might suit a particular individual better than another. The specialist may be able to advise whether there is any advantage associated with a particular drug.
At present acetylcholinesterase inhibitors are only used in people with mild to moderate Alzheimer's disease. They are not effective for everyone and may only temporarily improve memory or delay memory loss. Research is being undertaken to find out whether any of these drugs may be effective in the later stages of Alzheimer's disease.
In February 2006, following a positive opinion from the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency, the European Commission granted rivastigmine EU Marketing Authorization for the symptomatic treatment of mild to moderately severe dementia associated with idiopathic Parkinson's disease (PDD).
The action of memantine is different to that of the acetylcholinesterase inhibitors. Memantine blocks another neurotransmitter in the brain known as glutamate. Glutamate is released in excessive amounts when brain cells are damaged by Alzheimer's disease, causing the brain cells to be damaged further. Memantine is thought to protect brain cells by blocking this release of excess glutamate.
Memantine can temporarily slow down the progression of symptoms in people in the middle and later stages of the disease. This is the first time a drug has been available for this group of people. There is also a suggestion that memantine may slow down the disease process itself.
At first memantine was licensed for the treatment of moderately-severe to severe Alzheimer’s disease, but following a positive opinion from the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency in October 2005, the European Commission granted memantine an extension of the indication to the treatment of patients with moderate to severe Alzheimer’s disease.
Last Updated: Friday 14 November 2014