Pyridostigmine drug information

General information about pyridostigmine

For

• Patients
• Staff

Drug and brand names

• Mestinon (pyridostigmine bromide)

Formulations

• Film coated tablet (strength 60 mg)

Uses

• Pyridostigmine is used for the symptomatic treatment of myasthenia gravis. Please note this medication is also used for paralytic ileus and post-operative urinary retention. This document is intended for patients where this medication is only being used for myasthenia gravis.
• Myasthenia gravis (sometimes abbreviated to MG) is a chronic autoimmune condition which causes muscle weakness and excessive muscle fatigue.
• There are two main forms of myasthenia, ocular and generalised, depending on which type you have will depend on which muscles are affected.
• The following symptoms can present in ocular myasthenia gravis:
  - drooping of eyelids (ptosis)
  - double vision (diplopia)
• The following muscles can be affected in generalised myasthenia gravis:
  - face and throat muscles, affecting smiling, speech, chewing and swallowing
  - neck muscles
  - limb muscles
  - breathing muscles
• Myasthenia gravis symptoms can typically worse at the end of the day, in hot weather, during or in the interim phase post an infection or during menstruation.
• Pyridostigmine is a first line treatment for myasthenia gravis and can help to bring timely symptom relief.

How does my medication work?

• Pyridostigmine belongs to the group of drugs called ‘anticholinesterases’.
• There is an enzyme in the body called ‘acetylcholinesterase’ which breaks down the chemical acetylcholine. Acetylcholine allows communication between nerves and muscles.
• Pyridostigmine reduces the activity of acetylcholinesterase and thereby helps to increase and prolong the action of acetylcholine, which in turn enhances the stimulation of smooth and skeletal muscles.
• This medication works quickly (within 30 minutes) and the effect lasts for up to four hours. You are most likely to have this medication prescribed every three to four hours during your treatment. Dosages range from 30 to 180mg. On first starting treatment, your dose will remain low, be regularly monitored and if tolerated well, it is likely to increase.
• A challenge with this therapy is that too high a dose can actually make patients weaker again, having initially improved on lower doses. This is because too much acetylcholine can cause weakness. We call this a ‘cholinergic crisis’. It can sometimes be hard to determine whether a patient is suffering a cholinergic crisis (dose too high) from a flare up of their myasthenia. Your prescriber will therefore closely monitor your response to this medication.

Side effects

This list is not exhaustive; please also refer to product literature.

• In general, pyridostigmine is tolerated well by patients. However, as with all medication, there is always a risk of side effects, though it is unlikely that you will experience these. Please alert your prescriber if you notice any new adverse effect straight after first starting pyridostigmine so this can be assessed.
• Most commonly this medication can cause ‘muscarinic’ side effects, most notably increased sweating, increased salivary and gastric secretions, and increased gastrointestinal and uterine motility (causing colic, abdominal pain and diarrhoea) and bradycardia. There is another medication we can use to help improve (or sometimes eliminate) these side effects, this is known as propantheline. Propantheline is usually taken 30 minutes before the dose of pyridostigmine to help these side effects.
• If you notice any of the above symptoms are particularly pronounced during your treatment, alert your neurologist or specialist neurology nurse as soon as possible so this can be assessed.

Please note there are signs / symptoms that you may experience due to the myasthenia itself getting worse rather than your medication. More information on this is provided below:

• Please note it is important to understand that myasthenia gravis differs in severity and distribution of weakness between individuals; symptoms can fluctuate, with relapses and remissions.
• Worsening of myasthenia can occur for many reasons and can occasionally be life-threatening. When severe, we call this a myasthenic crisis.
• It is also important to be aware of possible signs of myasthenic crisis and to seek emergency medical attention if any of these occur:
  - saliva building up in your throat making it difficult to breathe
  - inability to swallow
  - jaw or tongue weakness
  - nasal tone to your voice
  - your airways feel blocked

Please ensure any above signs or symptoms of myasthenic crisis experienced are reported as a matter of urgency to your neurologist or specialist neurology nurse, and seek immediate medical attention.

Contraception

There is not enough evidence within studies to confirm the safety of pyridostigmine in this setting. It is recommended you and your partner ensure adequate effective contraception whilst you are on this medication.

Pregnancy and breastfeeding

The safety of pyridostigmine during pregnancy or lactation has not been established. However, if this medication is used during pregnancy your doctor will advise you regarding the potential benefits of therapy and potential harm to your unborn baby. This medication has been used before in pregnancy and has revealed no untoward effect thus far.

Pyridostigmine does cross the placenta barrier. For this reason it is likely your doctor will avoid using excessive doses during your pregnancy.

It has been indicated only negligible amounts of pyridostigmine are excreted in breast milk. Please discuss with your prescriber if you wish to continue breastfeeding during this treatment.

Drug interactions

• Aminoglycoside antibiotics, local and some general anaesthetics, antiarrhythmic agents and other drugs interfere with neuromuscular transmission and have the potential to interact with pyridostigmine.
• It is important to note there are many medications which may trigger or worsen myasthenia gravis, some of which are contraindicated for use for patients with myasthenia. Please always highlight your condition to your prescriber when starting any new medications. Your doctor and pharmacist will be able to provide further advice on medication safety.
• Methylcellulose can completely inhibit absorption of pyridostigmine and it is not advised concomitantly alongside pyridostigmine.

Other useful information

• The tablets should be swallowed whole with a little liquid, with or without food.
• In the event of swallowing difficulties, tablets can be halved or quartered to help administration. Alternatively, tablets crushed to a fine powder and added to water will give an even dispersion which can be taken.
• These tablets contain lactose.
• Extreme caution is required when administering pyridostigmine to patients with obstructive respiratory diseases like bronchial asthma and chronic obstructive pulmonary disease (COPD).
• Caution should also be taken within patients with arrhythmias, recent coronary occlusion, hypotension, vagotonia, peptic ulcer, epilepsy, parkinsonism and hyperthyroidism.
• This medication should be stored below 25°C within the original package to protect it from light and moisture.
• This medication is contraindicated in mechanical gastrointestinal or urinary obstruction.
• Pyridostigmine is contraindicated in patients with hypersensitivity to the active substance, bromides or to any of the excipients.

Contact information

If you have any questions or concerns, please contact the specialist neurology nurse on 01223 349363.

Please note

The information on this leaflet is not exhaustive. Please refer to the patient information leaflet prepared by the manufacturer of your drug which can be found in the medicine packaging.