Muscle cramps

after a reoccurence of cancer, and a second set of radiation treatments, and currently recieving chemothearapy treatments(cisplatin) and (adriamycin)my mother in-law is experiancing Terrible muscle cramps at night and recently during the day. The pain is horrible, and lasts for about 15 min. I am wondering if anyone else has experianeced this, and if so, what they may have done to alleviate this pain.
Thanks