<prompt> Enuresis persists, and the patient is placed on desmopressin acetate DDAVP. This medication works which of the following mechanisms?Decrease detrusor muscle toneImproves aleness of the patient during the sleep cycleIncrease external sphincter contractionIncrease water permeability and reabsorption in collecting tubules  <response>: Desmopressin, or DDAVP, can be used intranasally in patients suffering from enuresis. This medication is a long-acting synthetic analogue of vasopressin. The medication acts at V2 receptors, which are found on renal tubule cells, and mediates an anti-diuretic effect by increasing water permeability and water reabsorption in the collecting tubules, leading to decreased urine output. It is effective in 70 of patients with increased nocturnal urine output. Detrusor muscle tone is under control of the parasympathetic system. DDAVP does not affect this system. Some sympathomimetic drugs may cause enough wakefulness so that the child perceives the urge to void . Dextroamphetamine sulfate is one such medication. The external sphincter is under somatic nervous control. This medication does not contribute to this system. Ref: Goldson E., Reynolds A. 2012. Chapter 3. Child Development Behavior. In W.W. Hay, Jr., M.J. Levin, R.R. Deterding, J.J. Ross, J.M. Sondheimer Eds,CURRENT Diagnosis Treatment: Pediatrics, 21e. 