[Neuromuscular effects of vecuronium in patients receiving long-term administration of dantrolene].

We report two patients who received anesthesia using vecuronium (VCB) subsequent to long-term treatment with orally administered dantrolene. The present data suggest that these doses used of dantrolene do not prolong the duration of neuromuscular blockade induced by VCB. An 8 year old boy was given general anesthesia after medication with 20 mg.day-1 of dantrolene orally for two years. Anesthesia was induced with thiamylal and maintained with nitrous oxide in oxygen and halothane. The neuromuscular blocking effect of vecuronium was evaluated using mechanomyogram (Myograph 2000, Biometer). The potency of VCB was in the normal range and the duration and recovery time were not prolonged. A 49 year old male had been treated with 50 mg.day-1 of orally administered dantrolene for several years prior to the operation. Anesthesia was induced with thiamylal and maintained with nitrous oxide in oxygen and isoflurane. The neuromuscular blocking effect of VCB was monitored by the same method as described above. Again, there was no apparent prolongation of neuromuscular blocking action of VCB. Evidently, VCB may be used in the clinic under standard conditions of neuromuscular monitoring in patients under previous long-term treatment with dantrolene.