Side effects of Mestinon may include diarrhea, increased production of saliva and mucus, and a slowing of the heart rate. This drug is helpful to most people with MG, but the benefits tend to decrease over time. Some people are unable to tolerate the side effects at an effective dose level. Immunosuppressant drugs are another effective treatment for MG, and may be combined with cholinesterase inhibitors. The most commonly used drugs are prednisone and azathioprine.
Prednisone usually brings about rapid improvement.
Once maximum improvement is achieved, the prednisone dose is reduced very gradually to the minimum effective dose, but it rarely can be eliminated entirely. This is important, since prednisone's side effects can be significant. These may include weight gain, cataracts, gastrointestinal ulcers, mood changes, hypertension and osteoporosis. Azathioprine is a very slow-acting drug, and maximum improvement may take several months to a year or more to achieve. Side effects can include decreased activity of the bone marrow, liver toxicity and flu-like symptoms.