Currently, four drugs are available that can improve memory and delay disease progression in Alzheimer's disease. The first three drugs belong to the class called cholinesterase inhibitors (ChE-I) and are represented by donepezil (Aricept), rivastigmine (Exelon), and galantamine (Reminyl). In addition to these memantine (Ebixa) has been linked to neuroprotective effects that alter the course of the illness and improve certain areas of functioning.
It is important to see these medications in the correct perspective. The cholinesterase inhibitors are expensive and will cost between R350 and R1 200 per month. Generic products for Aricept are currently the cheapest in South Africa.
The cholinesterase inhibitors work by inhibiting an enzyme called cholinesterase, thus increasing the concentration of the chemical acetylcholine in the brain. They have two main benefits; they improve memory and improve functioning in daily activities.
However, not everyone will experience the improvement. Most studies indicate that about 40 to 50 % of people experience a 1-5 point improvement on the Mini Mental Status Examination test. Most people will experience a delay in the progression of the illness. Functioning in activities of daily living improves and caregivers will notice this change. They have also shown that people on these treatments require fewer additional drugs to manage the psychological and behavioural aspects of the illness.
The benefits are more prominent in the early stages of the illness and many scientists say that the benefits in advanced illness are, at most, modest.
The cholinesterase inhibitors are also beneficial in mild cognitive impairment (MCI). In this condition the medication can delay conversion to dementia.
Cholinesterase inhibitors should be prescribed as early as possible in Alzheimer's disease. The medication should be used throughout the illness and may be stopped during advanced stages of the disease. The recommended dose for Reminyl is 8 mg per day, for Aricept 10 mg a day, and for Exelon, the highest tolerable dose, which may be 12 mg a day.
These drugs seem to be equally effective and if an inadequate response is seen on one drug, it may be an indication to switch to another drug. Side effects consist of nausea, vomiting, diarrhoea, gastric upsets, fatigue, dizziness, headache, and increased nasal secretions. Studies have shown that Reminyl and Aricept have fewer side effects than Exelon.
Ebixa works by blocking NMDA glutamate receptors. This helps to minimise the impact of toxic increases in the activity of glutamate in the brain. Ebixa has also been linked to slowing the deterioration of the illnesses, improving activities of daily living and particularly social and language areas of function.
These drugs have changed our thinking about Alzheimer's disease. Most doctors used to be pessimistic about the illness, but now we have something to fight back with and to actually improve symptoms and functioning.
Written by Dr Frans Hugo, MBChB, M.Med Psychiatry and Dr L. Van Wyk, MBChB, M. Med (Psych) from the Panorama Memory Clinic
Reviewed by Dr Michael S. Mason, MB ChB, FC Psych (South Africa), Consultant Psychiatrist in Private Practice at Panorama Psychiatry and Memory Clinic, September 2011
For more information visit: Dementia SA: http://www.dementiasa.org/ or Alzheimer’s South Africa: http://www.alzheimers.org.za