I take Synthroid. I was on Zoloft. I found out that the Zoloft was causing problems with my TSH. You should talk with your docs about this.
http://www.thyroid.org/patients/brochures/hypothyroidism%20_web_booklet.pdf
Check out this too. It has literature on Zoloft and thyroid.
You should take your Synthroid in the morning on an empty stomach and then wait at least an hour to eat anything.
You should keep most other meds at least four hours away from the Synthroid if you can. I can't.
I don't know if Zoloft will mess with the Synthroid.
Calcium is a big no-no in the morning.
Vitamins should be spaced several hours away, like lunch time.
There are other specifics, too, but I forget.
Sometimes you have to compromise a little.
The key is consistancy. If you do it the same way every day, and there is a conflict that affects Synthroid absorbtion, at least it is the same every day.