Pyridostigmine for myasthenia gravis

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.