The prolonged duration of the SCh effect after pancuronium is probably due to the known inhibition of cholinesterase by pancuronium. The short duration of action after Atracurium and Vecuronium can be explained by the competitive antagonism at the receptor causing an increased amount of unbound SCh. The duration of the SCh effect may be influenced according to clinical needs by the choice of the non-depolarizing muscle relaxant. The significantly reduced duration of complete neuromuscular block after Atracurium or Vecuronium as precurarizing agents may be advantageous in cases where a fast recovery of spontaneous breathing is essential. If a reduction of the SCh blockade has to be avoided, Pancuronium should be selected for prior administration.