^ and has been mentioned in the past potentiating with certain things can increase the neurotoxity (for example altering your urine ph to slow excretion). That said, in the week before rolling it's healthy to pre-load with vitamins, take magnesium to reduce muscle spasms/gurning, and 5-htp (but not within 24 hours of dosing or it'll dull the experience). One thing that does seem to have an effect on the high is piracetam. I haven't tried other nootropics though.
Note: one should never try to potentiate MDMA with DXM or a MAOI.