A comparison of the onset time, duration of action, and fade characteristics of atracurium and vecuronium.

The speed of onset (T1 = 95% twitch depression) and the duration of action (T1 = 25% control) of equipotent doses of atracurium 0.5 mg/kg and vecuronium 0.1 mg/kg were compared in 21 ASA physical status I and II adult patients. Train-of-four (TOF) ratios (height of T4/T1) were also compared with the first response in the TOF recovered to 25% and 50% control, respectively. Neuromuscular function was measured by the Datex NMT 221 electromyograph at the hypothenar muscles. No significant difference was seen in the onset of action of these two drugs, but a significantly shorter duration of action was observed with vecuronium (P < 0.5). Vecuronium was also found to exhibit significantly more TOF fade on offset of block than atracurium. Vecuronium may offer a distinct advantage over atracurium when a nondepolarizer is required for a relatively short clinical case. However, it appears that vecuronium causes more TOF fade during recovery from neuromuscular blockade than atracurium.