Acetylcholinesterase Inhibitors

Reviewed by: HU Medical Review Board | Last reviewed: September 2023

The first drug often prescribed for mild to moderate myasthenia gravis (MG) is an acetylcholinesterase inhibitor. Other names include cholinesterase inhibitors, anticholinesterases, or anticholinesterase drugs.1,2

Pyridostigmine bromide was first created in 1945 in Switzerland and gained widespread use as a myasthenia gravis treatment in the 1950s.3

How do they work?

These fast-acting drugs work by stopping the breakdown of acetylcholine. Acetylcholine is the chemical messenger that the nerve releases to tell a muscle to contract. In people with myasthenia gravis, the body attacks the neuromuscular junction (the area where acetylcholine flows), which decreases the muscles response to acetylcholine. Without enough acetylcholine signals, the muscles tire quickly when used.1,2

Anticholinesterases do not prevent the body from attacking the neuromuscular junction. These drugs prevent the breakdown of acetylcholine. This increases the levels of acetylcholine available to the muscles. This helps improve muscle strength.1,2

Many people with MG need to take an immunosuppressant, such as a steroid, along with their acetylcholinesterase inhibitor to fully control symptoms. Adding an acetylcholinesterase inhibitor may make it possible to take lower doses of steroids, which have more long-term side effects.1,2

Pyridostigmine comes in pill or liquid form. The intravenous (IV) form is given when someone cannot swallow, such as during a myasthenic crisis.2


The medicine most often prescribed for people with MG is pyridostigmine bromide (brand names Mestinon® or Regonol®).1,2

Another brand of acetylcholinesterase inhibitor is neostigmine (Prostigmin®), but this is prescribed less often.2

Possible side effects

Side effects can vary depending on the specific drug you are taking. These drugs also work very differently from person to person. Some people with MG see great improvement, while others see little benefit.2

Often, some muscles will show greater strength but not all muscles impacted by MG. For instance, someone may find that their neck weakness and droopy eyelid go away but not their double vision.2

Possible side effects of acetylcholinesterase inhibitors include:1,2

  • Stomach cramps
  • Diarrhea
  • Muscle twitching and cramps
  • Sweating
  • Too much saliva

Antidiarrheal medicines and other drugs may be prescribed to manage the stomach issues that sometimes come with these drugs.2

These are not all the possible side effects of acetylcholinesterase inhibitors. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with acetylcholinesterase inhibitors.

What is a cholinergic crisis?

A cholinergic crisis is a rare complication of taking high doses of acetylcholinesterase inhibitors. The main symptom is weakness, which can make it hard to tell from an MG flare or myasthenic crisis.2

Other things to know

People who have moderate to severe MG or MG that is quickly getting worse are often given treatments in addition to acetylcholinesterase Inhibitors. This includes plasmapheresis, IVIG, and large doses of immunosuppressants.2

Acetylcholinesterase inhibitors generally do not work for people with MuSK-positive MG.2

Before beginning treatment for myasthenia gravis, tell your doctor about any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.

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