I have read that they get high and crazy for 20 minutes, then need about half an hour to "reset", wherein they can start the process over again from baseline. (they don't get higher and higher, nor do they need increasing doses to achieve the same affect). Interestingly, Valerian root has the same active ingredient as catnip, as I found out one day when my kitty managed to open the pill container and spill them all over, eating some of them. Then she attacked me.