Use of intravenous pulsed cyclophosphamide in severe, generalized myasthenia gravis

Twenty-three myasthenia gravis (MG) subjects, mean (SD) age 41.6 years (14), showing poor disease control or steroid-related side effects, received treatment for 12 months with intravenous cyclophosphamide (CP; n = 12) or placebo (PL; n = 11) in a randomized, double-blind trial. Pulses were given monthly at an initial dose of 500 mg/m(2) of body surface, and titrated according to changes of peripheral muscle strength or side effects. Changes of muscle strength, steroid and pyridostigmine requirements, and development of ventilatory failure or swallowing impairment were evaluated at 0, 3, 6, and 12 months. No differences were observed between groups at baseline. Statistically significant reductions of methylprednisone doses were noted in both groups but were more pronounced in subjects receiving CP than PL at 6 months (P < 0.05) and at 12 months (P < 0.03). At 12 months, five subjects on CP had tapered off their steroids whereas no subject on PL achieved further reductions (P < 0.03). Four CP subjects were not receiving steroids 36 months after completing the study and three other CP subjects had stopped pyridostigmine. CP improved muscle strength at 3 and 6 months, and this reached statistical significance compared to PL at 12 months mainly in the bulbar and masticatory (P < 0.009) and extraocular muscles (P < 0.03). Ventilatory failure was noted in one subject on CP (due to bronchopneumonia) and two on PL (due to muscle weakness). No significant increases of CP-related side effects were observed. Thus, this study suggests that intravenous pulses of CP allow reductions of systemic steroids usage without muscle strength deterioration or CP-related side effects.