Fluoxetine belongs to which pharmacologic class?

• A. SNRI
• B. MAOI
• C. SSRI
• D. TCA

Answer: (C)

Fluoxetine is a selective serotonin reuptake inhibitor, an SSRI. It works by blocking the serotonin transporter, which reduces the reuptake of serotonin from the synaptic cleft back into the presynaptic neuron. This increases the amount of serotonin available to bind to postsynaptic receptors, helping to improve mood and anxiety symptoms in conditions like major depressive disorder and several anxiety disorders. Compared with other antidepressant classes, SSRIs focus specifically on boosting serotonin with a relatively favorable side-effect profile.

In contrast, monoamine oxidase inhibitors (MAOIs) work by blocking the enzyme that breaks down monoamines, leading to higher levels of several neurotransmitters but with dietary and drug interaction risks. Serotonin-norepinephrine reuptake inhibitors (SNRIs) increase both serotonin and norepinephrine in a similar way to SSRIs but with dual reuptake inhibition. Tricyclic antidepressants (TCAs) block reuptake of norepinephrine and serotonin but have broader side effects due to additional receptor interactions.