Is it a pm doctor that's telling you it's ok to take them together, or a psychiatrist? I'd want at least a second opinion from an expereinced psychiatrist with some pain management background. Sometimes doctors combine medications based on their clinical experience (experience with patients), not necessarily what a drug is created for. I'm not sure if these should be taken together, but I'm not sure they coudn't be in certain circumstances.
Well, that' a big help to you, right! (NOT) If you're not sure see if you can get more than one opinion, and do a little research on the medications yourself. See if the manufacturers say anything about contraindications with other medications. You might also ask the opinion of an experienced pharmacist.
Wish I could help more.
Sorry Jen - we must have been posting at the same time. Looks like you've already done your research. Have you asked your doctor WHY he thinks it necessary and ok to take them together? What's the benefit for you, and what are the risks? I think you're owed an explanation so you can make an informed choice. Good luck!