Everyday for the last month I have been experiencing sudden severe cramps in the back of both my thighs, that stops me dead in my track. I take metformin for medically induced diabetes. I had a heart transplant on March 2, 2013. My medications are as follows: Tacrolimus 6mg daily, Junivia, Bystolic, Calcium, Magnesium Oxide, Foilc Acid, Baby Aspirin, Allupurinol