Methadone is great for pain relief but the respiratory depressant aspects of it are some of the strongest I've ever experienced. I think a few of our members have tried rhe extended relief versions of both the hydromorphone and the oxymorphone and have reported good pain relief with both.
I haven't tried either in extended release, so I'm not of much direct help. I agree with Ashelen that you should talk to the doctor about it and see if one works with your lifestyle and pain levels more than others. I don't know if xanax is as much of an issue as a resp. depressant with those but it does depend on the dose and the patient.
Everything works differently for different people. Have you discussed with your doctor the risk of combining xanax and methadone? I was on a different benzo when on methadone but I also smoked at the time so I think that had something to do with the issues I had.
I think that combining Xanax with any of them runs the risk of CNS depression (respiratory problems) but it all depends on dosage, tolerance, and how frequently the meds are combined...... but your doctor can help you make this decision...hydromorphone, however (dilaudid) is fairly short-acting and i would not consider it a substitute for methadone, which has a significantly longer half-life...you may want to consider switching to something like MS Contin or OxyContin (two long acting meds) and continue with your roxicodone for breakthrough...but again, all of these are risky if you combine them with a muscle relaxer/anti-anxiety like Xanax....only you and your doctor can determine if you can safely combine them. And if you're truly in doubt about the safety or wisdom of combining them, ask a pharmacist! they generally have better knowledge of medications and side effects and risks than doctors do.