Cholinesterase Inhibitors

Cholinesterase inhibitors or acetylcholinesterase inhibitors are medications that prevent the breakdown of acetylcholine in the body. Cholinesterase inhibitors block the action of acetylcholinesterase. Acetylcholinesterase is an enzyme that breaks down acetylcholine to an inactive form. This reduces nerve cell communications in your body that use acetylcholine to help transmit cell to cell messages.

Acetylcholine is one of the chemicals that nerve cells use to communicate with one another in the brain, the central nervous system (CNS), and other areas of the body. Acetycholine affects learning, memory, and other cognitive function(s). Scientists think that reduced levels of acetylcholine in the brain causes some of the symptoms of Alzheimer’s disease. Blocking the enzyme that destroys acetylcholine with a cholinesterase inhibitor (anticholinesterase) increases the concentration of acetylcholine in the brain, and this increase may improve memory and cognitive function.

Doctors prescribe cholinesterase inhibitors to individuals with dementia caused by Alzheimer’s disease and dementia.

Doctors also prescribe them to individuals to treat Lewy Body dementia, Parkinson's disease, glaucoma, myasthenia gravis, and schizophrenia.

Some cholinesterase inhibitors are used as antidotes. Some can treat mild to moderate Alzheimer's disease, for example, rivastigmine (Exelon, Razadyne), while donepezil (Aricept) is approved to treat all stages, from mild Alzheimer's to severe Alzheimer's disease.

Some common side effects or adverse events of cholinesterase inhibitors are:

• Nausea
• Vomiting
• Diarrhea
• Muscle cramps
• Weight loss
• Headache
• Insomnia
• Abnormal dreams
• Hallucinations
• Confusion
• Fainting
• Fatigue
• Hypertension
• Frequent urination

Drugs that block the action of acetylcholine produce opposite effects to the effects of cholinesterase inhibitors. They may reduce the effect of cholinesterase inhibitors. Examples of such drugs include atropine, benztropine (Cogentin), and trihexyphenidyl (Artane).

Bethanechol (Urecholine) increases the effect of acetylcholine and therefore may add to the effect and side effects of cholinesterase inhibitors.

Cholinesterase inhibitors that are used in medicine are reversible cholinesterase inhibitors. Irreversible (also termed Quasi-irreversible) cholinesterase inhibitors are often used as pesticides or chemical weapons, for example, carbamate, metrifonate.

Brand and generic names of some FDA-approved cholinesterase inhibitors include

• donepezil (Aricept, Aricept ODT)
• tacrine (Cognex) (This medication is discontinued in the US)
• rivastigmine (Exelon, Exelon Patch)
• galantamine (Razadyne or formerly Reminyl)
• memantine/donepezil (Namzaric)
• ambenonium (Mytelase)
• neostigmine (Bloxiverz) for non-depolarizing neuromuscular blocking agents

Cholinesterase inhibitors have not been well studied in pregnant women. It is not known whether they are safe to use during pregnancy or while breastfeeding. If you are pregnant, check with your OB/GYN doctor before using any of these drugs.