when dancing in a club or rave You can become extremely dehydrated. MDMA causes an increased heat production by muscles and brain PLUS reduces body's ability to maintain core temperature PLUS hides body's thirst and exhaustion responses PLUS constriction of blood vessels near the skin. all of this together, means a complete bodily and psychological inability to know when You is dehydrated. it can lead to hyperthermic syndromes, heat stroke, hyperpyrexia (elevation of body temperature). then continuous hyperpyrexia can lead to rhabuomyolysis (skeletal muscle breakdown). rhabuomyolysis then leads to renal failure(kidney failure) and then death. yea swim knows that rhabuomyolysis is probably mispelled. here we have another problem.. knowing the effects of MDMA can lead to dehydration and knowing that You cannot feel it very well (if at all), You drinks alot of water, and sometimes too much water--- leading to water intoxication which causes hyponatremia (dilation of the blood causing swelling in the brain). sometimes water intoxication isnt always from drinking too much water. The release of vasopressin (i think from the pituitary glands), vasopressin goes to the renal (kidney) tubules. the end result of that leads to water retention.