Myasthenia gravis medical therapy

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Medical Therapy

Treatment is by medication and/or surgery. Medication consists mainly of cholinesterase inhibitors to directly improve muscle function and immunosuppressant drugs to reduce the autoimmune process. Thymectomy is a surgical method to treat MG. For emergency treatment, plasmapheresis or IVIG can be used as a temporary measure to remove antibodies from the blood circulation.

Medication

• Cholinesterase inhibitors: neostigmine and pyridostigmine can improve muscle function by slowing the natural enzyme cholinesterase that degrades acetylcholine in the motor end plate; the neurotransmitter is therefore around longer to stimulate its receptor. Usually doctors will start with a low dose, eg 3x20mg pyridostigmine, and increase until the desired result is achieved. If taken 30 minutes before a meal, symptoms will be mild during eating. Side effects, like perspiration and diarrhea can be countered by adding atropine. Pyridostigmine is a short-lived drug with a half-life of about 4 hours.

• Immunosuppressive drugs: prednisone, cyclosporine, mycophenolate mofetil and azathioprine may be used. It is common for patients to be treated with a combination of these drugs with a cholinesterase inhibitor. Treatments with some immunosuppressives take weeks to months before effects are noticed.

• Penicillamine

Plasmapheresis and IVIG

If the myasthenia is serious (myasthenic crisis), plasmapheresis is used to remove the putative antibody from the circulation. Similarly, intravenous immunoglobulins (IVIG) are used to bind the circulating antibodies. Both of these treatments have relatively short-lived benefits, typically measured in weeks.

Contraindicated medications

Myasthenia gravis is considered an absolute contraindication to the use of the following medications:

• Dicyclomine
• Glycopyrrolate
• Hyoscyamine
• Gemifloxacin mesylate
• Methscopolamine bromide
• Quinidine gluconate
• Orphenadrine
• Norfloxacin