Could Weight Loss Be Due To The Intake Of Flexeril?

I have been taking 20mg Oxycontin TID and 10mg Oxycodone TID for about 9 months. Pain management doctor three months ago added Flexeril to help minimize muscle spasms in my shoulder, source of the pain. I have had four surgeries on my left rotator cuff, repairs have not been effective due to poor tissue strength in the cuff. Rotator cuff is completely torn as is one bicep tendon. Since I started taking the Flexeril I am experiencing weight loss - 28 pounds, current weight is 119 pounds. I have started intake of Ensure in effort to slow this weight loss without success. Would the addition of the Flexeril possibly be a cause? Blood work is well within normal limits. I am 64 years old.