What is it used for?

• Myasthenia gravis.
• Difficulty passing urine (urinary retention) after an operation.
• Inactivity or temporary paralysis of the muscle in the intestines (paralytic ileus).

How does it work?

• Mestinon tablets contain the active ingredient pyridostigmine bromide, which is a type of medicine called an anticholinesterase. It works by prolonging the action of a neurotransmitter called acetylcholine.
• Neurotransmitters are chemicals that are stored in nerve cells in the brain and nervous system. They are involved in transmitting messages between nerve cells. Acetylcholine is involved in transmitting nerve messages that control many of the processes that happen automatically in the body, ie without our voluntary control. It is also involved in transmitting the nerve messages to muscles that cause them to contract.
• In order for the nerves to pass a message to a muscle, acetylcholine is released from the end of the nerve cell. It fits into acetylcholine receptors that are found on the muscle cells like a key into a lock. This causes changes in the muscle cells that cause the muscle to contract. The acetylcholine is then rapidly broken down by an enzyme called cholinesterase.
• In the condition called myasthenia gravis the body's immune system destroys many of the acetylcholine receptors on the muscle cells. This means that the muscle becomes less responsive to nerve messages and as a result, the person experiences muscle weakness, particularly when they repeatedly try to use the same muscle.
• Pyridostigmine stops cholinesterase from breaking down acetylcholine at the junctions between the nerves and the muscle cells. This prolongs the action of acetylcholine at the nerve endings and gives it more chance to act on the remaining acetylcholine receptors. Pyridostigmine thus increases the likelihood of a nerve signal being successfully transmitted to the muscle. It improves nerve transmission both to muscles that are under voluntary control, as well as those that are not, for example the muscle in the gut. It thus allows these muscles to function normally.
• The benefits of pyridostigmine occur within 30 to 60 minutes but wear off in three to four hours, so the medicine should be taken at regular intervals throughout the day to improve muscle function in myasthenia gravis.
• Pyridostigmine can also be used to improve nerve transmission to the muscle in the gut in people whose intestine is not working properly, or to the muscle in the bladder in people whose bladder is not working properly (for example following surgery).
• Inactivity or temporary paralysis of the muscle in the intestine prevents the passage of food through the intestine and can lead to a blockage in the gut. Pyridostigmine increases the nerve messages to the gut that make it contract and helps it move food along.
• Temporary paralysis of the muscle in the bladder makes it difficult to pass urine. Pyridostigmine increases the nerve messages to the bladder that make it contract, and this allows urination to happen.

How do I take it?

• Mestinon tablets can be taken with or without food. The tablets should be swallowed with a drink of water. The tablets can be cut or broken up into small pieces if you find them difficult to swallow.
• The dose prescribed and how often the medicine needs to be taken depends on the condition being treated. It is important to follow the instructions given by your doctor.

Warning!

• It is important that this medicine is stored in its original container. This will help to protect the tablets from light and moisture.
• Mestinon tablets contain lactose and may be unsuitable for people with lactose intolerance, glucose/galactose malabsorption or a genetic disorder leading to accumulation of galactose in the blood (galactosaemia).

Use with caution in

• Asthma.
• People who have recently had a heart attack.
• People with a slow heart rate (bradycardia).
• Low blood pressure (hypotension).
• A condition called vagotonia (where overactivity of the vagus nerve causes symptoms such as slow heart rate, low blood pressure, constipation, sweating and painful muscle spasms).
• Decreased kidney function.
• Epilepsy.
• Parkinson's disease.
• Peptic ulcer.

Not to be used in

• People with a physical blockage in the gut (intestinal obstruction).
• People with a physical blockage in the urinary tract (urethral obstruction).
• This medicine should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

• This medicine should be used with caution during pregnancy, and only if the expected benefit to the mother is greater than any possible risk to the developing baby. Seek medical advice from your doctor.
• This medicine passes into breast milk in amounts that are probably too small to be harmful to a nursing infant. However, as with all medicines it should be used with caution by breastfeeding mothers, and only if the benefit to the mother is greater than any possible risk to the baby. Seek medical advice from your doctor.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

• Abdominal cramps.
• Diarrhoea.
• Nausea and vomiting.
• Increased salivation.

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before using any new medicines while using this one, to make sure that the combination is safe.

It is important to tell your doctor that you are taking this medicine if you are going to have surgery. Pyridostigmine can stop the effect of certain medicines used to relax muscles during surgery (eg pancuronium, vencuronium) and prolong the effects of other muscle relaxants (eg suxamethonium).

The following medicines can oppose the effects of pyridostigmine:

• aminoglycoside antibiotics such as neomycin or gentamicin
• antimuscarinic medicines for Parkinson's symptoms, eg procyclidine, orphenadrine, trihexiphenidyl
• antimuscarinic medicines for urinary incontinence, eg oxybutynin, trospium, tolterodine
• atropine
• chloroquine
• clindamycin
• hydroxychloroquine
• hyoscine
• polymixin
• propafenone
• propranolol.

References:

http://www.medicines.ie/medicine/15028/SPC/Mestinon+60mg+Tablets/#MACHINEOPS

http://www.netdoctor.co.uk/medicines/aches-and-pains/a7086/mestinon-pyridostigmine/

http://www.medicinenet.com/pyridostigmine-oral/article.htm

http://www.rxlist.com/mestinon-side-effects-drug-center.htm

https://www.dailystrength.org/group/myasthenia-gravis/discussion/mestonin-increased