Remeron^® (mirtazapine) is a prescription medication that is approved to treat depression. It is not entirely clear how the medication works, but it is believed to help release more serotonin and norepinephrine (chemicals in the brain) that can become unbalanced. Possible side effects include drowsiness, weight gain, and dizziness. If side effects become too bothersome, or if the medication does not work as well as intended, alternatives to Remeron are available, including other antidepressants and therapy.