Zoloft (sertraline) is used for the treatment of depression, Doxycycline monohydrate anxiety, and obsessive-compulsive disorder. Launched in 1992, it has been used in over 10 billion patient days of therapy. Zoloft is a SSRI drug that increases the level of serotonin in the brain by inhibiting its breakdown. So why take Zoloft? Because it's an SSRI drug and Doxycycline monohydrate easier on your liver...