Cholinsterase is an enzyme that STOPS "excessive passage of nerve impulses from one nerve cell to another."
So while that would be good for constipation, it can also lead to muscle twitching, cramping, overstimulation of all kinds, because of these 'excessive nerve impulses'.
MSM should be avoided big time in anyone with anxiety, OCD, twitching, cramping, etc., -- including a 'racing heart' -- unless they're taking something that increases cholinesterase.