Good quality bioavailable magnesium/calcium supplements worked like a miracle for my cramps and fasciulations, my dad's (he also has PN), and my wife's leg cramps (she's PN free).

The ratio should be about 2 atoms of calcium for 1 of magnesium. Don't take more than 1,000 mg. total/day because too much may increase the risk of kidney stones. If you supplement with calcium/magnesium, also supplement with vitamin D (up to 40 mg./day) to enable the body to utilize the calcium/magnesium.