Name a drug that is a common example of a tricyclic antidepressant (TCA).

Amitriptyline is a classic example of a tricyclic antidepressant (TCA), which is a class of medications primarily used to treat depression. TCAs work by inhibiting the reuptake of neurotransmitters, mainly norepinephrine and serotonin, leading to increased levels of these chemicals in the synaptic cleft. This mechanism is thought to help improve mood and alleviate symptoms of depression.

In contrast to amitriptyline, fluoxetine and sertraline are selective serotonin reuptake inhibitors (SSRIs), which target serotonin specifically without significant effects on norepinephrine. Venlafaxine, on the other hand, is classified as a serotonin-norepinephrine reuptake inhibitor (SNRI), which is a different class altogether. While venlafaxine has some similar effects to TCAs, its mechanism and chemical structure place it outside the definition of traditional tricyclic antidepressants. Thus, amitriptyline stands out clearly as the quintessential example of a TCA.