What is a common side effect associated with the use of tertiary amine TCAs?

The correct answer highlights a notable side effect of tertiary amine tricyclic antidepressants (TCAs), which is QT prolongation. QT prolongation refers to an extension of the QT interval on an electrocardiogram (ECG), which can lead to serious heart rhythm abnormalities, including torsades de pointes, a life-threatening arrhythmia. This is particularly relevant for patients taking TCAs, as the potential for cardiac side effects underscores the need for careful monitoring, especially in those with pre-existing cardiac conditions or in combination with other medications that may also affect the QT interval.

While nausea, constipation, and anxiety can also occur as side effects of TCAs, they are not as specifically impactful or clinically significant as QT prolongation. Nausea is a common side effect associated with many medications, constipation is a frequent side effect of TCAs due to their anticholinergic properties, and anxiety may arise in some cases, but it is not typically identified as a primary side effect of these medications. The uniqueness of QT prolongation as a serious cardiovascular concern distinctly positions it as the correct answer in this context.