Which medication is classified as an SNRI?

Venlafaxine is classified as a serotonin-norepinephrine reuptake inhibitor (SNRI). This class of medications is primarily used to treat major depressive disorder and anxiety disorders. SNRIs work by increasing the levels of serotonin and norepinephrine, two neurotransmitters in the brain that are thought to play a key role in mood regulation.

The effectiveness of SNRIs like venlafaxine stems from their dual action of blocking the reuptake of both serotonin and norepinephrine, which can enhance mood and alleviate anxiety symptoms. This mechanism differentiates SNRIs from other classes of antidepressants, such as SSRIs (selective serotonin reuptake inhibitors), which primarily focus on increasing serotonin levels alone.

In contrast, the other medications listed in the options, such as sertraline (an SSRI), citalopram (an SSRI), and paroxetine (an SSRI), do not have the dual action aspect of SNRIs and primarily affect serotonin levels in the brain. Therefore, the classification of venlafaxine as an SNRI is correct due to its unique pharmacological profile and therapeutic uses.