How it works

Pyridostigmine (brand name Mestinon) is one of the most common medicines used to treat myasthenia symptoms. It is an AchE (Acetylcholinesterase) inhibitor. Acetylcholinesterase is the enzyme responsible for breaking down Acetylcholine. In patients with myasthenia, Acetylcholine is unable to bind to its receptor due to blockage by autoantibodies. By reducing levels of the enzyme responsible for breaking it down, Pyridostigmine increases the amount of free Acetylcholine in the body and therefore increases the rate of successful interaction.

How it is delivered

Pyridostigmine is available in tablet, syrup, and injectable form. Tablet-form Pyridostigmine can also come in a sustained-release version (SR), which can be useful at bedtime for patients symptomatic during the night or in the early morning.

When you have it

Pyridostigmine is generally taken every 6 hours during daytime hours, but this may vary based on advice from a neurologist and the type of medication prescribed. It takes around 30 minutes for the dose to take effect. Continue to take pyridostigmine as prescribed even if you feel well and do not stop taking this medication without consulting your neurologist.

Side Effects

Common: Upset stomach, diarrhoea, vomiting, drooling, pale skin, cold sweats, blurred vision, water eyes, increased urge to urinate, anxiousness and feeling of panic, muscle weakness. If any of these symptoms are severe, contact your doctor.

Adverse: Severe itching, skin rash, hives, slurred speech, confusion, seizures, difficulty breathing. If you experience any of these symptoms, call your doctor immediately.

Known UK suppliers


Report any side effect you have to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.

Click here to report a side effect to the MHRA.