Many antidepressants cause weight gain for some people. As for the detox tea, the problem with it is that as a liver cleanser it will cause the liver to shed toxins. Since most medication is seen as foreign and therefore toxic by the liver to varying degrees, and since the liver is necessary to metabolize antidepressants, it might wash out some of your medication before it has a chance to be absorbed. That could weaken the benefits you're receiving from it, or even throw you into withdrawal theoretically. I say theoretically because most detox teas are very weak liver cleansers, but there you have it.
One treatment of tea won't do anything. To detox, you have to do it for awhile, and they do wash meds from the liver. This is a standard warning.
Oh, and if you're talking about washing illegal drugs from the system to pass a drug test, detox tea won't do that, either. It doesn't act quickly enough. That's usually done with carbohydrate drinks, not mild detox teas.