Medications that affect serotonin levels in the brain have the potential to create a side effect called serotonin syndrome.His condition is caused by a buildup of serotonin in the brain, which leads to severe confusion, agitation, tremors, increased blood pressure, fast heart rate, and coordination loss.Without medical intervention, severe cases of serotonin syndrome can be life-threatening.Serotonin syndrome may be more likely if the drug is mixed with other drugs that affect serotonin levels like other SNRIs or selective serotonin reuptake inhibitors.