The other day I took 40mg of prescribed Escitalopram (although it was several months past its use by date). After a while I started feeling mildly anxious but generally everything was fine. Then later on I was outside and I started feeling very cold and nauseus, and also felt quite paranoid and anxious, with sounds seeming to echo slightly. I got what seemed to be mild hallucinations with visual things appearing odd. When I got home later I felt fuzzy and rather strange and all the lights seemed too bright. I was also yawning a lot. At one point I took my blood pressure and it was 150/90 with a heart rate of around 110. Later it dropped down to 140/80 but remained like this for the next day with the heavy yawning continuing. Even the next day my pupils were extremely DILATED. I have tried some hallucinogens (mushrooms) in the past, only a couple of times, and it was slightly similar to this. I am certain it was a form of serotonin syndrome/toxicity but I cannot understand how such a low dose of a fairly standard antidepressent medication could have brought this on. I am not taking anything else and have not taken anything like MAOI's recently. What do you think was causing this?