Lots of meds just don't seem to work for fibro. I got nothing from Robaxin but a headache. Flexeril put me to sleep but gave me serotonin syndrome with the tramadol I was taking.
Same story for pain meds. OTC just doesn't work. Neither do Rx antiinflamatories like Mobic. My pain med now is Vicodin which isn't working as well after being on it for 6 weeks. I had to stop the tramadol because it gave me serotonin syndrome when I needed a second pill.
Lyrica just made me gain a lot of weight. Neurontin seemed good for a while, but I stopped it when it interacted with tramadol, and I found out I felt so much better without it.
Trazodone helped with sleep but gave me restless legs. Lexapro gave me electric-like shocks in my back and legs. I don't tolerate codeine, Percodan, Fentanyl, Darvocet or Demerol - vomiting. Elavil gave me suicidal thoughts and I was told by my rheumy not to take any more antidepressants, ever.
I'm trying Cymbalta now, but the 30 mg dose is giving me a headache and no relief from pain at all, so when I go on the 60 mg I am not expecting anything good either. Cymbalta is giving me really bad insomnia too, even when I switched to taking it in daytime.
One muscle relaxant you probably haven't considered is Valium/diazepam. It's one of the oldest and really works well. It put me to sleep the first few times I took even 1/2 the lowest dose (lowest pill is 2 mg and is scored for breaking). It was prescribed for back spasms after I was in a wreck, and it works very well. It doesn't put me to sleep now at 2 mg and I can even function during the day with it. You can get hooked on benzos, but 1 or 2 mg isn't much. Lots of people are on 5 mg every night or even twice during the night because it only lasts 4 hours.
Over all, tramadol was the best for fibro muscle pain. It doesn't do enough for bone pain or surgical pain. (I have a lot of arthritis in my spine, pinched nerves, scoliosis, etc.) It doesn't help with sleep. But most people don't have as much sensitivity to serotonin as I do and can take multiple SSRIs and SNRIs, which I can't.
The trick is to find out which med is causing the side effects. I keep a detailed log of things I eat (food intolerances too), with meds and reactions. Never take two new meds at the same time! Try one for a while before trying the second one. From my log notes, I typed up a long list of the meds I have taken and my reactions. It's in the computer and I update it regularly. I take the list with me to all doctor's appointments. It's been really helpful to my pain docs!
It's like a Science Fair project/experiment. Each person is different - you can tell from reading the posts! So keep your data notebook (med log), and keep on experimenting! Good luck and keep posting.