Combining non-depolarizing neuromuscular blocking agents: synergism, addition or antagonism? 
As the quality of currently available relaxants has improved, the need to combine relaxants to minimize the incidence and severity of their side-effects has decreased.  Little work has been done in the past year characterizing the effects of combining different non-depolarizing neuromuscular blocking agents.  That which has been done sheds some light on the nature of their interactions.