Sensitivity to vecuronium after botulinum toxin administration

When used to treat focal dystonias, botulinum toxin may cause a transient impairment of neuromuscular transmission in muscles distant from those injected. These systemic effects are not clinically evident, but should not be ignored when patients are exposed to other drugs or conditions that also impair neuromuscular transmission. A patient is described who underwent general anesthesia twice during treatment with botulinum toxin for a long history of blepharospasm. On both occasions, the neuromuscular block produced by vecuronium (0.05 mg kg^-1) was monitored in the abductor digiti minimi muscle. Compared with that observed in 24 individuals who were free from neuromuscular problems, the patient's sensitivity to vecuronium was low 90 days after the seventh treatment with toxin and normal 8 days after the ninth. The possibility is considered that repeated treatments with the toxin may cause continuous remodeling of neuromuscular junctions and may cause the patient to develop some tolerance to the action of neuromuscular blockers.