Antidepressants are medications used to treat depression and prevent recurrence. They work by increasing levels of serotonin, norepinephrine, and other neurotransmitters through inhibiting reuptake. Tricyclic antidepressants and MAOIs increase neurotransmitter levels by inhibiting reuptake or the enzyme that breaks them down, while SSRIs selectively inhibit serotonin reuptake. Common antidepressants include imipramine, nortriptyline, fluoxetine, and sertaline. They are used to treat endogenous depression, depression with other illnesses, and conditions like anxiety and OCD. Nurses should monitor for side effects and educate patients on safe usage and gradual discontinuation.