ListenSpecific Dementia Medications
Cholinesterase inhibitors
Acetylcholine is a chemical substance occurring naturally in the brain that enables some of the brain’s nerve cells to pass messages to each other. Many people with Alzheimer’s disease have a reduced amount of acetylcholine. Cholinesterase inhibitors reduce the natural process of breakdown of acetylcholine, which boosts its functioning in the brain. These medications may also be appropriate for some people diagnosed with Dementia with Lewy Bodies, Parkinson’s disease with dementia, or some types of dementia caused by poor blood supply to the brain.
The cholinesterase inhibitors available in New Zealand are Donepezil (current brand name Ipca-Donepezil), Rivastigmine (current brands Rivastigmine Patch BNM, Arrowtex Rivastigmine Transdermal patch, and Exelon) and Galantamine (available as Reminyl). Donepezil is fully subsidised by PHARMAC and the Rivastigmine patch is fully subsidised for people who cannot tolerate Donepezil due to side effects. Prices of the unsubsidised brands and medicines vary from pharmacy to pharmacy. General Practitioners (and any other doctor) can prescribe any of these medications, as can appropriate Nurse Prescribers.
None of these medications cure dementia and they have no effect on how long a person with dementia will live for. Their main action is to stabilise some of the symptoms for a period. They may be especially useful for general motivation, for symptoms of psychosis such as delusions and hallucinations, and for aspects of ‘cognitive function’ (that is, memory and brain power). These medicines should be trialled for several months before deciding whether they have done any good, unless this is obvious quickly. Besides looking for improved symptoms, the prescribing doctor needs to measure any improvement in memory and related brain functions. Cholinesterase inhibitors may not be appropriate for some people already on medications prescribed for other health conditions.
Side effects may include loss of appetite, diarrhoea, nausea, worsening of stomach ulcers, slowed heart rate, dizziness on standing up, increased need to get to the toilet urgently to pass urine, insomnia, vivid dreams, fatigue, and muscle cramps. Donepezil and Galantamine come in tablet form but Rivastigmine is mainly available as a daily skin patch (to reduce side effects compared with tablets).
NMDA receptor antagonist
Memantine (brand name Ebixa) is a “glutamate inhibitor”. It targets the natural chemical substance glutamate, which can be present in high levels in the brain of a person with Alzheimer’s disease. Memantine may achieve its effects because it blocks the effects of excess glutamate at a specific site called the “NMDA receptor” and may prevent cell damage. This medication can be prescribed by any doctor or appropriate Nurse Prescriber. It is not subsidised and prices vary between pharmacies. Like the cholinesterase inhibitors, Memantine may reduce some dementia symptoms for some people, but it does not stop the progression of their dementia.
Immunotherapies
Various immunotherapeutic medications for dementia caused by Alzheimer’s Disease are becoming available in some parts of the world, especially a new drug called Lecanemab. Although this medicine and others like it are intermittently available via research trials in New Zealand, none of them been approved for general or specialist use here and none of them are subsidised. Their effectiveness is still under investigation. They require regular IV infusions in a supervised setting and complex monitoring including regular MRI scans due to significant risks including strokes and death.
Acknowledgements
- Drug treatments. Previous fact sheet of Alzheimer’s Disease International
- Perkins, Chris (2015) The New Zealand Dementia Guide Auckland NZ, Random House
- Ebixa (Memantine) – what is it? July 2008 Update sheet from Alzheimer’s Australia
- Thanks to Dr Matthew Croucher, Dementia Canterbury Medical Advisor
