<prompt> Cis-atracurium is preferred over atracurium, because:It has rapid onset of actionIt causes less release of histamineIt has short duration of actionIt has less depressant action on heart  <response>: Ans. B It causes less release of histamineRef: Millers 7the p869Both atracurium and cis-atracurium are non-depolarizing neuromuscular blockers.Both of these are intermediate acting agents both have same duration of action.Both of these agents are cardiostableAtracurium has faster onset of action as compared to cis-atracurium.Both are eliminated by Hoffmans elimination. Atracurium is also metabolized by liver to some extent and result in production of a metabolite laudanosine that can cause CNS toxicity including seizures. On the other hand cis-atracurium is almost completely eliminated by Hoffmans elimination and produce negligible laudanosine.Major advantage of cis-atracurium over atracurium is that the former do not release histamine.Note: Only cis-atracurium and doxacurium are the drugs in this category whose name ends with curium that do not release histamine. 