Yeah, it sounds like you did it backwards schwarcw. Same results though. There are many types of Absinthe. Most are premixed but some that you need to add vodka/spirits too. There is a big difference in the European versions, especially the French brands, as compared to other countries or the USA.
I will disagree with MB a little in that it does have some Hallucinogenic qualities that are equivalent to mild mushrooms. If you take enough you will "trip" slightly but the mental clarity is there. My friends and I have had multiple sessions with it and can attest to that.
Of course if you get the not so great absinthe you will probably end up drunk more then anything. Most absinthe's are supposed to be 100+ proof. But if you have the good stuff like SD has, several drinks, each containing one shot, will give you desired effect.