magnesium helps with body twitches etc. I get bad inner shakes (google it ) and i take magnesium.
as for pain. I suggest Panadeine 15. Strongest dose of codeine available OTC. The pharmacist will councel you on this but it is worth it. Very good OTC product.
i work in pharmacy but havent done retail for years. YAY for hospital pharmacy
a magnesium definency will result in cramps and tremours etc.