Hazards of neostigmine in patients with neuromuscular disorders. Report of two cases.

In a 57-yr-old female with dystrophia myotonica, attempts to reverse residual non-depolarizing block with neostigmine 1.0 mg were only partially effective and the administration of the further dose (0.5 mg) produced long-lasting muscle weakness. The train-of-four response of this patient resembled that of the depolarizing block and suggested an alteration in the electrical properties of the muscle membrane. A 50-yr-old male with a 30-yr history of progressive muscle dystrophy, exhibited a tonic response to neostigmine in the evoked mechanomyogram during recovery from partial neuromuscular block. It is concluded that the type of reaction to neostigmine in patients with neuromuscular disease in unpredictable.