As sarbanes said before, large doses of Tramadol (like 500mg, I know, I know, risk of seizures), first gives you a very very nice euphoria from the very powerful SSRI effects, until the drug becomes O-Desmethyl in the liver and its then when you have something like I could only describe as a very very long lasting and powerful Oxycodone feeling, plus the "happy" and "calming" and weirdness feeling of something like MDMA.... but it is truth that it doesnt work for every people.
I had 2 seizure in all my life because of mixing Codeine with large doses of Tramadol and it has been 2 years since I havent had any seizure, plus the side effects from withdrawal from Tramadol are not so bad like 3 or 4 years ago. I *always* take benzos with Tramadol, and only take one in the day if feel sleepy at work. Otherwise, there is no way im going to take more than 50mg of Tramadol without a benzo. And the benzo brand must be Roche, and it should be a short acting benzo like Alprazolam together with a long lasting benzo like Clonazepam.
500mg Tramadol, 6mg Alprazolam, 24mg Bromazepam, 50mg Diazepam, a good brand multivitamin while keeping you hydratated (A,B,C,D,E, etc. vitamins, Zinc, Magnesium, Electrolites, etc.) will achieve in some people one of the best highs of their life. I also recommend a little food (but just a little) before taking the pills.
I have taken Oxycodone, Morphine, IV Diazepam, IV Midazolam, Coke, Ketamine, Codeine+LSD, etc. etc. and sorry but nothing compares to a Tramadol combo so far. It lasts so long and its metabolite its so powerful that is really a wonder drug.
BTW, I have been between Tramadol withdrawals and I can compare them to benzo withdrawals. BEWARE.