Which medication is contraindicated for someone taking venlafaxine?

Venlafaxine is a serotonin-norepinephrine reuptake inhibitor (SNRI) commonly used to treat major depressive disorder and anxiety disorders. When considering medications that might be contraindicated for someone taking venlafaxine, it's essential to recognize the risk of serotonin syndrome, a potentially life-threatening condition that can occur with the combination of multiple serotonergic agents.

St. John's Wort is an herbal supplement that is known to have serotonergic properties. When taken concurrently with venlafaxine, it can increase the levels of serotonin in the brain beyond what is considered safe. This increases the risk for serotonin syndrome, which is characterized by symptoms such as agitation, confusion, rapid heart rate, dilated pupils, muscle rigidity, and in severe cases, seizures or even death.

In contrast, the other choices do not present the same risks. Fluoxetine is another antidepressant that impacts serotonin levels but is often monitored when used with venlafaxine, and manageable under medical supervision. Fentanyl is a potent opioid pain medication and doesn’t have significant interactions leading to increased serotonin levels. Amitriptyline is a tricyclic antidepressant that also affects serotonin but, like fluoxetine, may be used judiciously in a clinical setting with appropriate