Which of the following medications is classified as a selective serotonin reuptake inhibitor (SSRI)?

Celexa is classified as a selective serotonin reuptake inhibitor (SSRI) because it primarily works by increasing the levels of serotonin in the brain by inhibiting its reuptake into the presynaptic cell, thereby enhancing mood and alleviating symptoms of depression and anxiety. SSRIs like Celexa are commonly prescribed due to their effectiveness and generally favorable side effect profile compared to older antidepressants.

In contrast, the other medications listed serve different purposes or belong to different classes of drugs. Elavil is a tricyclic antidepressant, which affects multiple neurotransmitters and is often used for depression and chronic pain. Nardil is a monoamine oxidase inhibitor (MAOI), which works by inhibiting the enzyme that breaks down serotonin, norepinephrine, and dopamine, but is associated with dietary restrictions due to potentially serious interactions. Cymbalta, while it also treats depression, is classified as a serotonin-norepinephrine reuptake inhibitor (SNRI) and works by affecting both serotonin and norepinephrine levels, thus differing from the specific mechanism of SSRIs.