Nephrogenic diabetes insipidus is a physiologic condition in which the kidneys fail to concentrate urine despite adequate amounts of antidiuretic hormone (ADH). Central, or pituitary-dependent, diabetes insipidus develops when there is a lack of ADH production. Animals with central diabetes insipidus can be given desmopressin acetate. The nasal spray formulation can be used, with 1–4 drops administered into the conjunctival sac once or twice daily. Alternatively, the parenteral form can be given at 0.5–2 mcg, SC, once or twice daily. Thiazide diuretics may reduce polyuria by 30%–50% in animals with nephrogenic or central diabetes insipidus. Inhibition of sodium resorption in the ascending loop of Henle leads to decreased total body sodium and contraction of the extracellular fluid volume. The net effect is to increase sodium and water resorption in the proximal renal tubule. Chlorothiazide is given at 20–40 mg/kg, PO, bid.