I took Tramadol for bad back pain. I had the following side effects when I took the prescribe amount, when I stopped taking them they went away. I may have been unlucky as I don't see many other posts listing the same problems:
1. Eyes rolling up into my head.
2. Voice dropping unusually deep and low.
3. Becoming semi conscious (hearing sensitive like last thing at night before falling asleep and mind fully awake). Unable to keep eyes open, almost impossible to move. The conscious mind struggles to get the body to respond to its requests. Breathing becomes regular as if asleep.
The semiconsciousness could be fixed by lying down flat for around 20-30 minutes. Mental alertness and hearing are turned on during this time.
I took codeine before taking tramadol with no effects and when I took codeine again after having been on tramadol I did have side effects.