Hypomagnesemia
"I started this medicine at the suggestion of my D.O. as my magnesium levels were very low and I had bad leg cramps.  It did help the cramps quite a bit and my blood levels did return to normal.
However, I began to have bad bouts of nausea and vomiting and occasional diarrhea that I had to take additional medication to stop.  I took 400 mg but was never advised to take it with food. "