What is a common side effect associated with excessive doses of Citalopram?

Citalopram, which is a selective serotonin reuptake inhibitor (SSRI) used primarily to treat depression, can lead to QT prolongation when taken in excessive doses. This is significant because QT prolongation can increase the risk of developing a potentially life-threatening cardiac arrhythmia known as Torsades de Pointes. The mechanism behind QT prolongation involves alterations in the cardiac electrical activity due to the drug's effects on ion channels responsible for cardiac repolarization.

This side effect underscores the importance of monitoring patients on Citalopram, especially if they have other risk factors for cardiac issues or are taking other medications that might also prolong the QT interval. In contrast, the other options do not align with the well-documented side effects observed with excessive citalopram usage. Increased appetite and weight loss are generally not associated with the drug’s overdose symptoms, and while insomnia can occur, it is not specifically linked with high doses in the same way that QT prolongation is.