to distinguish central from DI due to the kidneys. Desmopressin is not effective at treating nephrogenic DI, thus a positive response is generally indicative of central DI. Side effects headaches facial flushing nausea hyponatremia seizures US drug regulators added warning to the nasal sprays after two people died and fifty-nine other people had seizures. This occurred due to hyponatremia, a deficit of the body's sodium levels, and the nasal spray is no longer approved for use in children in the United States. However, US drug regulators have said that desmopressin tablets can still be considered safe for treatment of nocturnal enuresis in children as long as the person is otherwise healthy. Patients must stop taking desmopressin if they develop severe vomiting and diarrhea, fever, the flu, or severe cold. Patients should also be very cautious about taking desmopressin during hot weather conditions or following strenuous exercise, as these conditions can place stress on the body's electrolyte and water balance. A body needs to maintain a balance of water and sodium. If sodium levels become too low (hyponatremia) – either as a result of increased water take-up or reduced salt levels – a person may have seizures and, in extreme cases, may die. Mechanism of action Desmopressin works by limiting the amount of water that is eliminated in the urine; that is, it is an antidiuretic. It works at the level of the renal collecting duct by binding to V2 receptors, which signal for the translocation of aquaporin channels via cytosolic vesicles to the apical membrane of the collecting duct. The presence of these aquaporin channels in the distal nephron causes increasing water reabsorption from the urine, which becomes passively re-distributed from the nephron to systemic circulation by way of basolateral membrane channels. Desmopressin also stimulates release of von Willebrand factor from endothelial cells by acting on the V2 receptor. It also increases endogenous levels of factor VIII, making it useful in the treatment of hemophilia A. Desmopressin is degraded more slowly than recombinant vasopressin, and requires less frequent administration. In addition, it has little effect on blood pressure, while vasopressin may cause arterial hypertension. Vasopressin stimulates the release of ACTH, which indirectly increases responsiveness of alpha-1 receptor in blood vessel smooth muscle, increasing vessel tone and blood pressure. Several studies have shown that Desmopressin does not stimulate ACTH release (except in Cushing's Disease), and therefore does not directly raise blood