Can I take my phentermine in the morning and Xanax (alprazolam) at night? I would never take them at the same time, but I was just wondering if this would be safe

Depends. On what you are taking the xanax (alprazolam) for. If it is for generalized anxiety disorder, unless you are on a time-release preparation, Alprazolam is a short-acting drug and will not be working for you if you take it at night. If it is for insomnia, it is not the best medication for sleep. If it is to combat the effects of the Phentermine making you anxious, again i would consider a longer acting drug.