I just got Rx called Cyclobenzaprine, 10mg. Its a muscle relaxer. A few years ago I got the same medication and it worked great. The medicine was a white tablet a few years ago. This present RX is a yellow tablet, same dosage. This yellow tablet has done nothing. Is there a difference in companies that make this medicine and why would my pharmacist give me this medicine if it doesn't work and I mean it doesn't work at all.