Surgeons use the drug succinylcholine, which is an acetylcholine analog, as a muscle relaxant. Care must be taken because some individuals recover abnormally slowly from this paralysis, with life-threatening consequences. These individuals are deficient in an enzyme called pseudochlinesterase, which is normally present in the blood, where it slowly inactivates succinylcholine by hydrolysis to succinate and choline.
If succinylcholine is an analog of acetylcholine, why do you think it causes muscles to relax, and not to contract as acetylcholine does?