What is the treatment of myasthenia?
Anticholinesterase drugs
More specific drugs for the treatment of myasthenia are anticholinesterases. They prevent acetylcholine from the neuromuscular junction is degraded, so that increases the amount of acetylcholine available to bind to acetylcholine receptors few that work properly. So improve nerve transmission to muscle and increase strength of muscle contraction. The anticholinesterase that is prescribed most often called pyridostigmine (Mestinon the trade name).
The improvement is seen in about 30-60 minutes and disappears within 3 to 4 hours. So we need to take pills several times during the day. The adverse effects of this medication include colicky abdominal pain and diarrhea, increased intestinal muscle activity. If this occurs, we recommend lowering the dose. In some patients, treatment with cholinesterase inhibitors is sufficient to control symptoms of the disease.Thymectomy
It is recommended to surgically remove the thymus when the patient has a thymoma. If this fails to remove the entire tumor, radiation therapy can be performed. However, symptoms may not improve after removal of myasthenia with thymoma.
It is also recommended removal of the thymus in young patients with generalized myasthenia, even without thymoma. This is because the remains of the thymus can produce acetylcholine receptor antibodies. Young patients who are in the initial stages of the disease are improving earlier after thymectomy.
The improvement usually occurs during the first year after thymectomy, but in some patients may take up to 3 years. There are patients who, after thymectomy, can suppress other medications or significantly reduce the doses (for example, cholinesterase inhibitors or corticosteroids).
Immunosuppression
Corticosteroids: those patients is not performed or do not respond to thymectomy are usually treated with corticosteroids. Corticosteroids decrease the activity of the immune system, which works in myasthenia gravis in excess. In general, you start with a small dose is increased gradually until the full dose. Sometimes, there is a transient worsening of symptoms when treatment is initiated. Once symptoms are controlled, the dose of corticosteroids was gradually reduced to find the lowest effective dose. This is the dose the patient should be taken permanently.
Steroids have many side effects that sometimes can be prevented by taking the proper medication. These include osteoporosis, which is a weakening of the bones, increased blood pressure and blood glucose level, and more prone to infections. Patients should never stop taking steroids abruptly. It is important that patients take some form of identification stating that taking this medication.
Agents save corticosteroids: Although corticosteroids are very effective in controlling the MG, often additional drugs are used so that the dose of corticosteroids needed is less, and if possible to avoid side effects. These include the azathioprine (Imurel), whose efficacy in myasthenia gravis has been demonstrated. There are other drugs that can be used in patients unable to take azathioprine, and methotrexate (Emthexate) or cyclosporine (Sandimmun). They, like steroids, increase the risk of infection, so patients should tell their doctor if they have fever or other signs of infection, and should not receive vaccines made with living microorganisms.
Emergency treatments
If the patient is very weak or have difficulty swallowing or breathing, you usually enter the hospital for plasmapheresis (a plasma exchange), or giving intravenous immunoglobulin. They produce a rapid improvement of symptoms, but short-lived (about 6 weeks). Therefore, it is best reserved for urgent situations which need a rapid improvement of symptoms. The long-term treatment with drugs should be made as described above.
credit to: Dra. María del Mar Carreño Martínez, Dra. Camilla Buckley, Dr. John Newsom-Davis
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