Respiratory arrest during therapy for premature labor in a patient with myasthenia gravis.

A case of premature labor in a woman whose pregnancy was complicated by myasthenia gravis is presented. Ritodrine was given for tocolysis, and betamethasone was administered to accelerate fetal lung maturation. An acute, life-threatening exacerbation of muscular weakness requiring intubation and mechanical ventilation occurred. It appears that betamethasone initiated the respiratory crisis. It is apparent, however, that tocolytic agents currently being used in patients with premature labor (namely, beta-2-sympathomimetics and magnesium sulfate) also have the potential to produce severe exacerbations of weakness, and even respiratory arrest in patients with myasthenia gravis. Each must be used with extreme caution if prescribed for women with this disorder.