Dying is possible under an active No-No Rush. On returning from hell, it claims you are still under No-no Effects but you do not get regeneration of either Mood or Energy.
(Died in this case smelting near my total energy limit)
Also, the No-No Rush status remains (beyond initial dosage time) until re-logging. Whereupon reverts back to normal No-No Powder Crash status ( Full mood and energy)