No effect from morphine and fentanyl

Just had cancer treatment and was given post-op morphine in two or three steps to provide pain relief. I wasn't really fully aware of the situation as I could have told the medical staff that morphine has previously brought zero pain relief in an A&E situation I had a few months ago. I was subsequently given fentanyl, which again, had no effect whatsoever.

I told them that I took Tramadol for chronic pain and was, subsequently, given 100 mg Tramadol and had pain relief within 15 minutes.

The question, therefore, is: why do morphine and fentanyl not work? I am aware that there is a genetic condition which could explain the matter. Why, however, would Tramadol work?

Could this be explained by one being a natural opioid derivative and the other a synthetic product?

Help is much appreciated.

I'm one of those morphine non-reactives. I've had it three times, absolutely no relief. I get nothing from codeine, not sure about fentanyl because it just makes me sick. I only get serotonin rise from tramadol, no pain relief, but it makes me happier. I got no pain relief from oxycontin either, stoopped it after many months and had no withdrawal. DILAUDID DOES WORK! You may need a pill to prevent nausea like I do with it.

My mom and son didn't, don't react to morphine either. I warned the family, because this is genetic! Some of my ancestors came from Norway. There's a study you can search that shows many people from there don't react to morphine.

Beg for Dilaudid, aka hydromorphone. but I need a whole milligram every hour or two every two hours. The hospital usually gives 0.2 mg, which does nothing!!! I need ten times that to get relief, but it does work!

I get some relief from Norco, aka hydrocodone. It's better than nothing, better than nsaids. Doc won't give e more than 2 x 7.5 mg a day. Not even the highest dose.

There are others who get nothing from any opioids. I hope you aren't one of those!

I haven't had good results from muscle relaxers either. The only one that worked gave me serotonin syndrome.

The best muscle relaxant is Valium. You may have luck with one of the other meds in the benzodiazepine group. Docs are nuts about prescribing benzos because they've been told it's addicting. Yes, if you have an addictive personality.

My pain doc is not telling me to stop ALL my pain meds and go on marijuana. But it doesn't work on "real pain" only on neuropathic pain, as far as I can see from reading for hours and hours.