The severe bronchospasm associated with rapacuronium, the cause is
Rapacuronium has effect on M2 and M3 muscarinic receptors in the bronchus. Activation of the postsynaptic M3 receptor by acetylcholine produces bronchoconstriction and the effect is terminated by presynooptic M2 receptors. Repacuronium blocks M2 receptor and has little effect on M3 so bronchoconstriction.
Allergic reaction
Massive histamine release
Unopposed action M3 muscarinic receptors in the bronchus.
M2 muscarinic receptor activation
Neuromuscular Blocker