Final answer:
Tricyclic antidepressants inhibit the reuptake of serotonin and norepinephrine to treat depression, with potential severe side effects and risk of fatal overdose.
Step-by-step explanation:
Tricyclic antidepressants (TCAs) like imipramine and amitriptyline are commonly used to treat major depression. They work by inhibiting the reuptake of neurotransmitters, particularly serotonin and norepinephrine. This action allows these neurotransmitters to remain in the synaptic cleft for a longer period, enhancing their mood-lifting effects. Clinically, besides depression, TCAs have some uses in treating anxiety and certain chronic pain conditions. However, they require careful monitoring due to potential toxicities, such as cardiovascular risks, anticholinergic effects, and a heightened risk of fatal overdose in comparison to newer antidepressants like selective serotonin reuptake inhibitors (SSRIs). Unlike SSRIs, TCAs have a narrow therapeutic index and can be dangerous if used in excess. Additionally, the side effects of TCAs are typically more severe than those of SSRIs and may include dry mouth, blurred vision, constipation, urinary retention, and cognitive disturbances.