Pyridostigmine for myasthenia gravis

About pyridostigmine

Myasthenia gravis is a condition where your muscles become easily tired and weak. There is a fault in the way nerve messages are passed from your nerves to your muscles. As a consequence, your muscles are not stimulated properly, so do not tighten (contract) well. The muscles around the eyes are commonly affected first. Myasthenia gravis is an autoimmune disease. This means that the fault is due to a problem with your immune system. Your immune system (which normally protects your body from infections) mistakenly attacks itself.

Your brain normally sends messages down nerves to the muscles it wants to contract. The nerve endings then release a chemical called acetylcholine. Acetylcholine quickly attaches to small areas on your muscles, called receptors, and this triggers your muscles to contract. In most people with myasthenia gravis, the immune system blocks or damages these acetylcholine receptors. The acetylcholine cannot then attach to the receptor and so the muscle is less able to tighten.

Pyridostigmine works by slowing the breakdown of acetylcholine when it is released from nerve endings. This means that there is more acetylcholine available to attach to the muscle receptors, and this improves the strength of your muscles. Pyridostigmine is the most commonly prescribed anticholinesterase.

Before taking pyridostigmine

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking pyridostigmine it is important that your doctor knows:

• If you are pregnant or breastfeeding.

• If you have asthma.

• If you have any of the following conditions: epilepsy, Parkinson's disease, an overactive thyroid gland or low blood pressure.

• If you have a heart condition, such as a slow heart rate, or if you have recently had a heart attack.

• If you have a stomach ulcer.

• If you have any problems with the way your kidneys work.

• If you feel you may have a blockage in your intestines, or if you have any difficulties passing urine.

• If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines.

• If you have ever had an allergic reaction to a medicine.

How to take pyridostigmine

• Before you start the treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about pyridostigmine and will provide you with a full list of the side-effects which you may experience from taking the tablets.

• Take pyridostigmine tablets exactly as your doctor tells you to. Your dose will be printed on the label of the pack to remind you about what the doctor said to you. It is usual for adults to take ½-2 tablets several times a day. The tablets take 30-60 minutes to start working and their effect will last for about 4-6 hours. Take the tablets at suitable intervals so that your muscles are strongest when you need to be the most active (for example, early in the morning and before meals). When pyridostigmine is prescribed for a child, the dose is calculated according to the age of the child.

• Swallow the tablet(s) with a drink of water.

• If you forget to take a dose at your usual time, take it when you remember. However, if it is just about time to take your next dose when you remember then leave out the forgotten dose and take your next dose when it is due. Do not take two doses together to make up for a missed dose.

Getting the most from your treatment

• Try to keep your regular appointments with your doctor. This is so your doctor can check on your progress.

• It is possible that you will be prescribed other medicines to take alongside pyridostigmine. You may be prescribed an immunosuppressant or corticosteroid medicine to help control your muscle symptoms. You may also be prescribed tablets to reduce side-effects if you are troubled by these.

• If you are having an operation or dental treatment, tell the person carrying out the treatment that you are taking pyridostigmine. This is important because pyridostigmine can interfere with some medicines used during surgery.

• If you buy any medicines, always check with a pharmacist that they are suitable for you to take with your other medicines.

Can pyridostigmine cause problems?

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with pyridostigmine. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

If you experience any other symptoms which you think may be due to the tablets, speak with your doctor or pharmacist for further advice.

How to store pyridostigmine

• Keep all medicines out of the reach and sight of children.

• Store in a cool, dry place, away from direct heat and light.

Important information about all medicines