The prohibited substances are vaguely enumerated (which is to say by catagory not specific drug) in CFR 391.41(b)(12)
As for depression drugs, they are not prohibited. However, depression may be a disqualifier, depending on a companies interpretation of CFR 391.41(b)(9)
"(b)(9) Has no mental, nervous, organic, or functional disease or psychiatric disorder likely to interfere with his/her ability to drive a commercial motor vehicle safely;"
This is an area where a letter from the treating doctor often comes in handy.
Since you don't suffer from depression, this should be a non issue. However, admitting that you are taking an antidepressant may well send up a red flag. Again, a letter from the treating physcian explaining the reason for the prescription would likely solve any problems.
for a full rundown of medical qulifications, see
http://www.fmcsa.dot.gov/rules-regul...ction_toc=1781