Final answer:
Tricyclic antidepressants (TCAs) like imipramine, amitriptyline, and nortriptyline are used for treating depression but carry a risk of toxicity, especially in overdose, leading to serious side effects including cardiac arrhythmias and seizures. They are now less commonly prescribed in favor of medications with safer profiles.
Step-by-step explanation:
TCA Toxicity and Tricyclic Antidepressants
Tricyclic antidepressants (TCAs) are a class of medications primarily used to treat major depression. Some well-known examples of TCAs include imipramine (Tofranil), amitriptyline (Tryptomer), and nortriptyline (Aventyl). These medications work by inhibiting the reuptake of neurotransmitters like epinephrine and serotonin, thereby increasing their levels in the brain and helping to elevate mood.
However, TCAs can be associated with significant toxicity, particularly when taken in overdose or in combination with certain other drugs. Symptoms of TCA toxicity may include drowsiness, confusion, cardiac arrhythmias, and in severe cases, seizures or coma. Due to these potential side effects and the risk of fatal overdose, TCAs are now less commonly used, and alternative treatments such as selective serotonin reuptake inhibitors (SSRIs) or psychotherapy are often preferred.
The chemical structure of TCAs closely resembles that of the phenothiazines; however, their distinct stereochemistry prevents the conjugation of the rings which imparts different pharmacological effects. While TCAs can cause sedation and blood pressure changes when given to non-depressed individuals, their mood-elevating effects become apparent when administered over a longer period to those with depression.