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An acetylcholinesterase inhibitor or anti-cholinesterase is a chemical that inhibits the cholinesterase enzyme from breaking down acetylcholine, so increasing both the level and duration of action of the neurotransmitter acetylcholine.
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Uses
Acetylcholinesterase inhibitors:
- Occur naturally as venoms and poisons
- Are used as weapons in the form of nerve agents
- Are used medicinally:
- To treat myasthenia gravis. In myasthenia gravis, they are used to increase neuromuscular transmission.
- To treat Alzheimer's disease
- To treat Lewy Body Dementia
- As an antidote to anticholinergic poisoning
Examples
Reversible inhibitor
Compounds which function as reversible competitive or noncompetitive inhibitors of cholinesterase are those most likely to have therapeutic uses. These include:
- Organophosphates
- Metrifonate (irreversible)
- Carbamates
- Phenanthrene derivatives
- Piperidines
- Donepezil, also known as E2020
- Tacrine, also known as tetrahydroaminoacridine (THA')
- Edrophonium
Comparison table
| Inhibitor | Duration1 | Main site of action1 | Clinical use1 | Adverse effects1 |
|---|---|---|---|---|
| Edrophonium | short (10 min.) | neuromuscular junction | diagnosis of myasthenia gravis | |
| Neostigmine | medium (1-2 hrs.) | neuromuscular junction |
|
visceral |
| Physiostigmine | medium (0.5-5 hrs.) | postganglionic parasympathetic | treat glaucoma (eye drops) | |
| Pyridostigmine | medium (2-3 hrs.) | neuromuscular junction |
|
|
| Dyflos | long | postganglionic parasympathetic | historically to treat glaucoma (eye drops) | toxic |
| Ecothiopate | long | postganglionic parasympathetic | treat glaucoma (eye drops) | systemic effects |
| Parathion (irreversible) | long | none | toxic |
Quasi-irreversible inhibitor
Compounds which function as quasi-irreversible inhibitors of cholinesterase are those most likely to have use as chemical weapons or pesticides. These include:
Natural Compounds
Effects
Some major effects of anticholinesterase inhibitors:
- Actions on the autonomic nervous system, that is parasympathetic nervous system will cause bradycardia, hypotension, hypersecretion, bronchoconstriction, GI tract hypermotility, and decrease intraocular pressure.
- SLUD syndrome.
- Actions on the neuromuscular junction will result in prolonged muscle contraction.
Titration phase
When used in the central nervous system to alleviate neurological symptoms, such as rivastigmine in Alzheimer's disease, all cholinesterase inhibitors require doses to be increased gradually over several weeks, and this is usually referred to as the titration phase.2
See also
References
- ^ a b c d Unless else specified n boxes, then ref is:Rang, H. P. (2003). Pharmacology. Edinburgh: Churchill Livingstone. ISBN 0-443-07145-4. Page 156
- ^ Inglis F. “The tolerability and safety of cholinesterase inhibitors in the treatment of dementia.” Int J Clin Pract. 2002;(127):45-63. PMID 12139367
External links
- ATSDR Case Studies in Environmental Medicine: Cholinesterase Inhibitors, Including Insecticides and Chemical Warfare Nerve Agents U.S. Department of Health and Human Services
- MeSH Acetylcholinesterase+inhibitors
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Wikipedia content modification information:
- This page was last modified on 2 November 2008, at 18:20.
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