ATRACURIUM AND VECURONIUM: EFFECT OF DOSE ON THE TIME OF ONSET

The time intervals measured from the administrations of eitheratracurium or vecuronium to maximum or 95% neuromuscular blockade(T_max) were compared in 70 patients using the evoked compoundaction potential of the adductor pollicis muscle. Equipotentdoses, calculated from the relationship between dose and responsefor both drugs obtained in an earlier study, were compared.The doses of atracurium and vecuronium ranged from 0.135 to0.5 mg kg^–1 and from 0.02 to 0.1 mg kg^–1, respectively.The dose range for both drugs included the ED₅₀, ED₉₅ and thedose required to produce 100% blockade (ED_"100"). No significantchanges in mean T_max occurred for doses of atracurium in therange 0.135–0.2 mg kg^–1 and in the range 0.24–0.5mg kg^–1. Similarly, no change in T_max occurred at dosesof vecuronium in the range 0.02–0.05 mg kg^–1 and0.06–0.1 mg kg^–1. T_max, changed significantly inthe dose ranges atracurium 0.2–0.24 mg kg^–1 andVecuronium 0.05–0.06 mg kg^–1. There was no significantdifference in T_max when equipotent doses of atracurium and vecuroniumwere compared.