Sensitivity to Second Dose of Mivacurium

Abstract

Summary The sensitivity of patients to a second dose of mivacurium has been studied following complete recovery of the twitch response after > 95% neuromuscular block produced by a systemic bolus of the drug. In further experiments we have excluded one arm from the effect of a systemic bolus ED95 dose of mivacurium for 100 s so as to obtain two different levels of neuromuscular block in the two arms of the same patient. Upon recovery from the block in the paralysed arm the dose response of both arms to a second dose of mivacurium was studied in order to investigate the effect of the amount and duration of block upon second dose sensitivity. An approximately 50% diminution in the ED95 dose requirement of mivacurium was found following complete recovery from an ED95 dose in spite of the rapid plasma clearance of this drug. A similar increase in sensitivity was observed in the arm that had been excluded for 100 s from the peak effect of the drug. It was concluded that the second dose sensitivity was not due to a receptor effect or to residual drug in plasma.