Here's what is working for my wife right now......doesn't stop the fasciculations, but it does help with the cramps quite a lot (she still has them sometimes, but can usually make it through the night....or, most of the night). Anyway, Nighthawk mentioned Magnesium Citrate. My wife takes Magnesium Oxide. It is very reasonably priced, and does a good job, so far......no guarantees, but worth a try. Also, she takes a lot of aspirin.....yep, just plain ol' 325mg aspirin. 2 at a time, every three hours (thereabouts). Believe it or not, the aspirin is amazing. And cheap......also worth a try. Our Dr. said she could have up to 8 doses (two aspirins) in 24 hours. She is taking usually 6 doses, sometimes 7 in 24 hours, and up to 4 of the Mag/Ox in that same 24 hour period (basically, one with every other dose of aspirin).
Everyone is different, good luck!