What is a contraindication for the use of venlafaxine?

The use of venlafaxine is contraindicated in patients who are concurrently using monoamine oxidase inhibitors (MAOIs) due to the risk of developing serotonin syndrome. Venlafaxine is classified as a serotonin-norepinephrine reuptake inhibitor (SNRI), and when combined with MAOIs, which also increase serotonin levels, there is a significant potential for an additive effect that can lead to this life-threatening condition. Serotonin syndrome is characterized by symptoms such as confusion, rapid heart rate, dilated pupils, loss of muscle coordination, or muscle rigidity, which can escalate quickly and require emergency treatment.

While there are other considerations for the use of venlafaxine, such as caution in patients with a history of hypertension due to the drug's potential to raise blood pressure, it is the interaction with MAOIs that presents a critical contraindication, as it poses an immediate risk to patient safety.