Anticholinesterase Inhibitors

• What are Anticholinesterases?
• What are Anticholinesterases used for?
• How do Anticholinesterases work?
• Side effects of Anticholinesterases
• Precautions when taking Anticholinesterases
• Interactions with other medicines
• Anticholinesterases

What are Anticholinesterases?

Anticholinesterases are a class of drugs that decrease breakdown of acetylcholine (a chemical messenger in the brain) and can be used in conditions whereby there is an apparent lack of this messenger transmission such as in Alzheimer’s disease. Members of this class include :

• Reminyl (galantamine)
• Aricept (donepezil)
• neostigmine
• Mestinon (pyridostigmine) and Elexon (rivastigmine).

What are Anticholinesterases used for?

Reminyl (galantamine), Aricept (Donepezil) and Exelon (rivastigmine) are used in the treatment of mild to moderately severe dementia. They help slow down the progression of dementia and improve alertness to reduce carer burden. They do not change the underlying disease. Studies have shown continued benefit for up to 4 years.

How do Anticholinesterases work?

The cognitive dysfunction (memory, attention, learning) in dementia of the Alzheimer type is related to a significant reduction in acetylcholine (a chemical messenger in the brain) transmission. Reminyl (galantamine), Aricept (Donepezil) and Exelon (rivastigmine) work by inhibiting an enzyme called acetylcholinesterase. By blocking this enzyme the breakdown of acetylcholine, released by the remaining healthy brain cells, is slowed down leaving more chemical messengers available to support normal brain function. In addition, Reminyl (galantamine) also increases the action of acetylcholine on another receptor site called nicotinic receptors. This has been associated with improved cognitive function.

Side effects of Anticholinesterases

The anticholinesterases are associated with prominent gastrointestinal adverse effects, particularly anorexia, nausea and vomiting. These occur in approximately:

• 20% to 40% of patients treated with Exelon (Rivastigmine)
• 10% to 15% of patients treated with Aricept (Donepezil)
• 3% to 17% of patients treated with Reminyl (Galantamine)

Some common side effects that may occur in approximately 1-10% is

• Diarrhoea
• Vivid dreams
• Cramps
• Dizziness

Some serious side effects that may occur in less that 1% is

• Gastrointestinal ulceration
• Gastrointestinal haemorrhage
• Mild pancreatitis

Your doctor may try to minimise the adverse effects by slow titration of dosage. Talk to your doctor if you are concerned.

Precautions when taking Anticholinesterases

Care should be taken when using these medications in patients with:

• Asthma and chronic obstructive airways disease – may increase shortness of breath.
• Cardiac conduction abnormalities – anticholinesterases can slow the heart
• Peptic ulcer – Because of their pharmacological action, cholinesterase inhibitors may be expected to increase gastric acid secretion.
• Severe renal impairment – may require individual dose titration.

Talk to your doctor if you are concerned about any of these.

Interactions with other medicines

This class of medications can interact with other medicines. Your doctor may try and avoid the combination or monitor you. If you have any concerns talk to your doctor or pharmacist about it. Anticholinesterases may slow the heart; administration with other drugs which can cause this may increase the risk of bradycardia (very low heart rate) and hypotension (very low blood pressure); heart rate and BP may be monitored. Always tell your doctor or pharmacist if you are on any other medications.

Anticholinesterases

• Reminyl (galantamine)
• Aricept (donepezil)
• Neostigmine (neostigmine)
• Mestinon (pyridostigmine)
• Elexon (rivastigmine)

References

1. Australian Medicines Handbook. [online]. Anticholinesterases. January, 2007. Available at URL: http://www.amh.net.au (last accessed 05/08/07).
2. Therapeutic Guidelines: Psychotropic. [online]. Drugs used in Dementia. Version 5, 2003. Available at URL: http://www.tg.com.au (last accessed 05/08/07).
3. MIMS Australia. [online]. Reminyl. 2007. Available at URL: http://www.mims.com.au (last accessed 05/08/07).
4. MIMS Australia. [online]. Exelon. 2007. Available at URL: http://www.mims.com.au (last accessed 05/08/07).
5. MIMS Australia. [online]. Aricept. 2007. Available at URL: http://www.mims.com.au (last accessed 06/05/07).