I'm immune to the hydromorphone actions, but not other opioids such as demerol (meperidine hydrochloride) (meperidine) or morphine?

Sounds confusing: In that hydromorphone is metabolized into morphine, and that is the effective agent in our bodies. There are people who may lack the enzymes to metabolize certain drugs, and this has been reported in some people with codeine, where the enzyme that metabolizes it to morphine is absent. It is possible you have something similar. Sometimes it is that you have not gotten the right dose by right route.