Azathioprine, an oral medication that suppresses the immune system, is a treatment for myasthenia gravis and other conditions.

How azathioprine works

Autoimmune conditions like myasthenia gravis involve the immune system producing  autoantibodies that attack tissue or organs. Normal antibodies attack only invaders like bacteria or viruses. The autoantibodies in myasthenia gravis attack and damage acetylcholine receptors, which are responsible for the control of muscle movement.

Azathioprine disrupts the formation of DNA, decreasing the production of new cells. Azathioprine especially hampers the growth of white blood cells. By stopping the growth of white blood cells, whose role is to make antibodies, azathioprine reduces the production of harmful autoantibodies.

Azathioprine in clinical trials for myasthenia gravis

Only a few clinical trials have looked at how well azathioprine combats myasthenia gravis. But the medicine has been used successfully for years to treat the condition. And 70 to 75 percent of patients with myasthenia gravis who receive azathioprine alone or in combination with corticosteroids usually respond well to treatment.

Scientists are still investigating azathioprine’s ability to counter myasthenia gravis. For example, a Phase 3 clinical trial (NCT01727193) is looking at its effectiveness and safety.

Participants with either generalized or ocular myasthenia gravis can participate in the study. For the first two weeks, all patients will be given daily doses of 36 mg/kg of pyridostigmine, another medication used to treat Myasthenia gravis, and 0.25 mg/kg of corticosteroids in addition to either 50 mg a day of azathioprine or 20 mg a day of leflunomide, another immune-suppressant. Doses of azathioprine and leflunomide may be increased in the following two weeks. If no side effects occur, patients will be kept on these medication regimens for a year.

The study is recruiting participants in China. It is scheduled to end in January 2020. The First Affiliated Hospital of Sun Yat-Sen University in GuangZhou is conducting it.

Further details

Azathioprine is a potent medication. Common side effects include fatigue, nausea, vomiting and mild fever. The overall activity of the immune system, liver and pancreas may also be affected, so regular blood tests are necessary to check for these serious side effects.

Several common medications may interact with azathioprine, such as allopurinol (used for gout), ACE inhibitors (usually used for heart, blood vessel, and kidney problems) and warfarin (used for blood thinning).

Azathioprine has to be taken for long periods, and it usually takes months for improvements in myasthenia gravis symptoms to become noticeable.

It is also used to prevent organ rejection after a transplant and in treating rheumatoid arthritis.

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