Good morning I am new to taking MS Contin it’s short term until I can get my MRI for my shoulder and hips for severe chronic pain.

I am on 15 mgs once a day will I feel relief the first time I take it or does it take a while to take effect ? also I was prescribed tizanidine for my constant muscle spasms can I take both around the same time or would they have life threatening effects ?

Any information would be greatly appreciated!