Especially at high serum levels, these antibiotics may increase neuromuscular block in patients with latent or manifest defects in neuromuscular transmission. Long-term penicillamine treatment may cause a reversible syndrome that clinically and electromyographically resembles myasthenia gravis. Treatment consists of removing the drug or toxic agent and providing necessary respiratory support and intensive nursing care. Atropine 0.4 to 0.6 mg po tid decreases the bronchial secretions in patients with cholinergic excess. Stiff-man syndrome is characterized by the insidious onset of progressive stiffness in the trunk and abdomen and, to a lesser degree, in the legs and arms.
Patients are otherwise normal, and examination detects only muscle hypertrophy and stiffness.
Electromyography shows only the electrical activity of normal contraction. Only symptomatic therapy is available. Diazepam is the only drug that consistently relieves muscle stiffness. Results of plasmapheresis are conflicting. Isaac's syndrome is a disorder of unknown cause that produces predominantly limb symptoms.