The dichloride salt of doxacurium. It is a mixture of the (1R,2S,1'S,2'R), (1R,2S,1'R,2'S) and (1S,2R,1'S,2'R) stereoisomers (a meso isomer and two enantiomers, respectively) of 2,2'-[(1,4-dioxobutane-1,4-diyl)bis(oxypropane-3,1-diyl)]bis[6,7,8-trimethoxy-2-methyl-1-(3,4,5-trimethoxybenzyl)-1,2,3,4-tetrahydroisoquinolinium] dichloride, all of which are in a trans configuration at the 1 and 2 positions of the tetrahydroisoquinolinium rings. A competitive neuromuscular blocker, it is used to provide muscle relaxation in general anaesthesia and to facilitate mechanical ventilation in patients in intensive care.