An anticholinesterase is a chemical that inhibits a cholinesterase enzyme from breaking down acetylcholine, so increasing both the level and duration of action of the neurotransmitter acetylcholine.

Anticholinesterases occur naturally as venoms and poisons, are used as weapons in the form of nerve agents, and are used medicinally to treat diseases such as myasthenia gravis and Alzheimers disease, and as an antidote to anticholinergic poisoning. In myasthenia gravis, they are used to increase neuromuscular transmission.

Compounds which function as reversible competitive or noncompetitive inhibitor s of cholinesterase are those most likely to have therapeutic uses. These include:

• Organophospate s
  • metrifonate
• Carbamates
  • physostigmine
  • neostigmine
  • pyridostigmine
  • ambenonium
  • demarcarium
  • rivastigmine
• Phenanthrine derivatives
  • galanthamine
• Piperidines
  • donepezil, also known as E2020
• Tacrine, also known as tetrahydroaminoacridine (THA')
• edrophonium

Compounds which function as quasi-irreversible inhibitor s of cholinesterase are those most likely to have use as chemical weapons or pesticides. These include:

• Organophosphates
  • echothiophate
  • isoflurophate
  • diisopropyl fluorophosphate
  • cyclosarin
  • sarin
  • soman
  • tabun
  • VX
  • VE
  • VG
  • VM
  • diazinon
  • malathion
  • parathion
• Carbamates
  • aldicarb
  • bendiocarb
  • bufencarb
  • carbaryl
  • carbendazim
  • carbetamide
  • carbofuran
  • chlorbufam
  • chloropropham
  • ethiofencarb
  • formetanate
  • methiocarb
  • methomyl
  • oxamyl
  • phenmedipham
  • pinmicarb
  • pirimicarb
  • propamocarb
  • propham
  • propoxur