For mild cases, for patients in partial remission after thymectomy, and for purely ocular myasthenia, the use of anticholinesterase drugs may be the only form of therapy necessary for some period of time (ocular myasthenia often responds well to small doses of corticosteroids as noted further on). Although these drugs seldom relieve symptoms completely (the response of ocular symptoms is typically incomplete), most such patients are able to function well.
Glucocorticoids For the patient with moderate to severe generalized weakness who is responding inadequately to anticholinesterase drugs, the long-term administration of corticosteroids is the most consistently effective form of treatment, as described in a large series of patients by Pascuzzi and colleagues. Small doses of corticosteroids (prednisone 15 to 25 mg daily) alone or in combination with azathioprine (see later) are also often adequate to control ocular myasthenia. However, one must be prepared to contend with the side effects of long-term corticosteroid therapy and we hesitate to undertake such a program in children or patients with severe diabetes or other diseases that are likely to be aggravated. Because recent experience with the newer immunosuppressive agents was not incorporated into most prior series, the uniform use of steroids might not be correct.
The usual form of corticosteroid therapy is prednisone (or corresponding doses of prednisolone), beginning with 15 to 20 mg/d and increasing the dose gradually until a satisfactory clinical response is obtained or until a daily dose of 50 to 60 mg is reached. With higher doses or more rapid elevations of the doses, worsening of weakness in the first weeks may occur and hospitalization and careful observation for respiratory difficulty may be advisable. Improvement after the initiation of corticosteroids occurs over a few weeks. Once the maximal effect from prednisone has been attained, the dosage can be reduced gradually over months to the lowest point at which it is still effective. Our practice has been to then attempt to institute an alternate-day schedule, which diminishes the side effects; some patients have done better with a modest difference in dose from 1 day to the next, rather than omitting a dose entirely on alternate days. Potassium supplements and antacids should be prescribed liberally if needed, as with any chronic corticosteroid regime and consideration should be given to prophylaxis with antibiotics for Pneumocystis infection, and bisphosphonate for osteoporosis if long-term treatment is anticipated. At the outset of steroid therapy, anticholinesterase drugs are given simultaneously; as the patient improves, the dosage of the latter may be adjusted downward.