I take St. John's Wort - the herb supplement - for anxiety/depression and I was reading about it's potential to interact with dextromethorphan - found in cough medicines/syrup. It says it can cause serotonin syndrome. I didn't know about this before I took two teaspoons of Robitussin DM - with dext. being the active ingredient - earlier and now I'm feeling quite strange. Headaches, a little derealised, confused, nauseous, jittery, tingley, sad, weak, slight chest pain every once in a while. It's taking alot of strength just to get up out of this chair. Is this normal or am I experiencing an interaction? Should I be worried? I also take Valerian Root.