Mivacurium chloride and myasthenia gravis.

We describe the successful use of the short-acting, non-depolarizing neuromuscular blocking agent, mivacurium, in a patient with myasthenia gravis taking pyridostigmine 120 mg four times daily. Increased sensitivity to mivacurium was demonstrated using train-of-four monitoring. A dose of 0.5 times the recommended ED95 (3.0 mg) resulted in 93% block of T1. Spontaneous recovery was prolonged with a recovery index (25%-75% T1) of 20.5 min. Residual block was antagonized without difficulty using neostigmine 2.5 mg. We discuss the relationship between plasma cholinesterase, acetylcholinesterase and anticholinesterase drugs.