I Was Prescribed This Med For Muscle Cramps In The

I was prescribed this med for muscle cramps in the legs and feet that I experience during the night time. I have RA so this was prescribed by my rheumatologist. The day after taking this med, I awoke to the muscles in my arms that were so sore I literally could not pickup a cup of coffee. The upper arms and across the upper back have remained very sore and ice packs or heat have not reduced the soreness. It is less so after I get up and move around some. My PMD told me to not take anything during this time that I do not usually take on a daily basis, but asked me to drop the 1/2 20 mg of Crestor. Are these sore muscles related to this med Tizanidine? Thanks for your help. Mary Posan