The bromide salt form of vecuronium, a synthetic steroid derivative of the naturally occurring alkaloids of curare with a muscle relaxant property. Vecuronium bromide competes with acetylcholine for the nicotinic receptors at the neuromuscular junction of skeletal muscles, thereby inhibiting the action of acetylcholine and blocking the neural transmission without depolarizing the postsynaptic membrane. This leads to skeletal muscle relaxation and paralysis.