Discussions that mention synthroid

Weight Loss board

I have used phentermine in the past but now I want to take the 15 mg dose but I am on several medications. Synthroid for underactive thyroid, Yasmin (birth control) and Doxycycline which is an antibiotic. My question is: Has anyone ever had any bad drug interactions w/ phentermine? Or know of any? Also, any allergic reactions? Thanks for the help. :D