I am suprised that no-one has mentioned the anti diuretic effect that mdma has (inability to urinate) this can really get quite horrible. Usually happens at higher doses. Iv done a whole g before on a rare occasion and once or twice gone a little higher. Complete waste of good crystal. The euphoric, empathatic nice ecstasy effect seems to wear off after the third dose at around 6hours maybe and from then on you get stimulation, slight trippyness and alot more anxious. Iv only hammered away at it due to tolerance and chasing the high frustration. Its not worth it unless you want brain zaps, sleep paralysis for weeks after.
Anyway back to the anti diuretic effect. I had a particularly nasty experience a while back. Could not urinate for at least 12 hours probably more. It seemed worrying as in the past this effect is usually overcome after a few hours. This time it wasnt and was worried i could get water poisoning. Yes we had done a stupid amount. That is probably why. I asked for help in ED that day, was genuinely worried.
http://www.bluelight.ru/vb/threads/603552-MDMA-urination-problem