Duration of action of supplemental doses of vecuronium is related to the duration after the initial dose.

Vecuronium was administered in an initial dose of 0.1 approximately 0.3 mg.kg(-1) and in supplemental doses of 0.03 mg.kg(-1) or 0.05 mg.kg(-1) in 74 patients (ASA class 1 or 2) scheduled for abdominal surgery. The duration of the neuromuscular blockade provided by vecuronium after both the initial and supplemental doses was determined using the evoked integrated electromyographic device. A statistically significant positive correlation (correlation coefficient: 0.83 approximately 0.91) was found between the duration of action of the initial dose and that of the first to fourth supplemental doses. The regression lines of each of the first four supplemental doses to the initial dose were very similar to each other. These results suggest that, since the duration of action of supplemental doses of vecuronium was prolonged in patients showing a long duration of action of the initial dose, it would be wise to avoid blind adherence to a predetermined schedule for supplemental administration. Rather, anesthesiologists should take into account the patient's response to the initial dose and then decide the most appropriate timing for supplemental doses. Moreover, since vecuronium shows little cumulative effect even after 4 supplemental administrations in clinical-range doses, it can be concluded that vecuronium can be safely used in a wide dose range.