I have been prescribed 40mg of Prozac for the past two years but, due to the side effects, my doctor is considering changing to a new generation anti-depressent NSRI which firstly affects neurodrenaline. I am concerned about the 'switching' period because Prozac has such a long half-life. I am also concerned about seretonin sydrome. Can NSRIs be introduced while SSRIs are still int he system?