I am guessing that you see two different doctors. One for weight loss and one for your ADHD/anxiety. I say this because
Basically phentermine is a stimulant (works like adderall), but works differently then adderall. I am not sure you should be taking it with adderall. "Phentermine use is containdicated in those who are:
Taking amphetamine (i.e. Adderall, Dexedrine, Vyvanse), in the last 14 days"
This quote is from - http://en.wikipedia.org/wiki/Phentermine
I find it very hard to believe that when Phentermine use is containdicated in those who are taking amphetamine (i.e. Adderall) that your doctor would say that they would not interact.
And Topamax is prescribed for antipsychotic-induced weight gain.
I have a feeling that your weight doctor is only going by a standard recommendation of weight loss meds, with out having a clue about other meds. So talk with your psyc first. While doing so - ADHD does cause weight gain due to impulse eating. It may be that you are underdosed on your Adderall. Switching to something like Vyvanse which lasts a lot longer might be a more effective (and safer way) to lose weight. Check this link to see if your ADHD medication is actually working for you the way it should be. http://www.additudemag.com/slideshow/212/slide-1.html?utm_source=eletter&utm_medium=email&utm_campaign=march
Essentially, I don't think that you can take both together. But, I am not a doctor. Which is why I recommended you talk to a doctor who bothers to read labels. Hope this helps. Best wishes and please feel free to ask if you have any more questions.
I'm not sure that you need all of this medication. I take Vyvanse, which is frequently prescribed for both ADD/ADHD and binge eating disorder. I don't take it for weight loss, but I know that it is often used for that purpose. I agree that the two medications you are on seem like an odd combo. I took Adderall in the past but felt very jittery and anxious. Vyvanse does not give me that feeling. Additionally, although I was not looking for something to help with weight loss, I did lose quite a bit of weight. In other words, there may be 1 medication to solve both issues. Just a thought....