Which of the following is a well-known TCA?

The correct answer is Imipramine (Tofranil), which is a well-known tricyclic antidepressant (TCA). TCAs are a class of medications that are primarily used to treat major depressive disorder and other mood disorders. Imipramine is one of the earliest and most studied TCAs, renowned for its efficacy in alleviating depressive symptoms. Its mechanism of action involves the inhibition of norepinephrine and serotonin reuptake, which enhances the availability of these neurotransmitters in the synaptic cleft, thereby improving mood.

In contrast, the other medications listed do not fall into the TCA category. Duloxetine (Cymbalta) is a serotonin-norepinephrine reuptake inhibitor (SNRI), which works similarly to TCAs but is a different class of medication. Escitalopram (Lexapro) and Sertraline (Zoloft) are both selective serotonin reuptake inhibitors (SSRIs), which specifically target serotonin reuptake without the broader effects on norepinephrine that is characteristic of TCAs. Each of these other medications has unique indications, mechanisms of action, and side effect profiles, which differentiate them from TCAs like Imipramine.