Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. It s not safe to take these medications together. Taking Pristiq together with Zoloft can increase the risk of a serious condition called the serotonin syndrome which is characterized by symptoms such as confusion, hallucination, seizures, increased blood pressure and heart rate, fever, excessive sweating, muscle stiffness, tremor, in-coordination, stomach cramp, nausea, vomiting, and diarrhea. In its severe form it cause coma and even death. You should seek immediate medical attention if you experience these symptoms while taking the medications or consult your treating doctor for an alternate effective medication instead of Pristiq. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Mohammed Taher Ali