I have sometimes severe muscle cramps in my legs and back. In the first several months after my MG diagnosis I was taking Mestinon and it did help for a while, then stopped working and the side effects of gas and nausea became worse, so I have stopped taking it and will use is only as a "rescue drug" as needed. My PCP recommended apple cider vinegar (or pickle juice) for cramps. I've been taking 3 capsules per day of the apple cider vinegar and it has helped. I also am drinking Propel to add electrolytes (recommended by my neurology PA) and that has helped as well. I also find getting enough good sleep makes a difference. In my case, I fairly sure the cramps are a side effect of prednisone and azathioprine that I am taking.