Corticosteroids benefit both generalised and ocular myasthenia (1). An alternate day strategy is recommended, when starting corticosteroid therapy, to avoid side effects. A low dose should be used to start with because of the risk of exacerbation of steroid-induced exacerbation of weakness: this effect does not seem to occur with steroid use in Lambert-Eaton syndrome.
- patients with generalised MG are usually admitted to hospital to initiate immunosuppression (2) - this is because a significant number of patients experience a marked deterioration in symptoms when high-dose prednisolone is initiated (possibly to the point of requiring assisted ventilation (2))
- initial dose of prednisolone should be small, e.g. 5mg, and increased slowly at a rate of 5-10 mg per week until either the symptoms are controlled or a maximum dose of 1.5mg per kg or 100mg on alternate days, whichever is the lower (2) is reached. Serum potassium should be monitored, in case potassium supplementation is required. Once improvement has been achieved, the dose may be reduced gradually, e.g. 5mg/month, to avoid precipitation of a relapse.
Except in those patients in whom the long-term controlling dose of prednisolone is likely to be low, other immunosuppressants that enable a reduction in the steroid dose (steroid-sparing agents) are also employed in the management of this condition.
- azathioprine was the first steroid-sparing agent shown to be effective in myasthenia gravis; however more recent studies suggest that methotrexate, ciclosporin and mycophenolate mofetil may be suitable alternatives (2)
Notes:
- if purely ocular symptoms, then steroids can be initiated as an outpatient but the dose is increased more slowly and the patient should be warned about the risk of deterioration in symptoms.
Reference:
- Prescribers' Journal 2000; 40 (2): 93-98.
- Prescriber 2005; 16(6): 39-47.