The main mechanism that can cause loss of fluid in the body would be from sweating and from urinating. Pathological causes that might cause loss of body fluid like diarrhea and bleeding.
Drugs that induce sweating is called diaphoresis. Drugs that induce urine production called diuretic.
If the question is ask for the name of condition where the body loses fluid it can be dehydrated or shock(more severe than dehydrated).
