A primary deficiency of AVP(vasopressin) secretion usually results from agenesis or irreversible destruction of the neurohypophysis. It is referred to variously as neurohypophyseal DI, neurogenic DI, pituitary DI, cranial DI, or central DI. The signs and symptoms of uncomplicated central DI can be eliminated by treatment with desmopressin (DDAVP), a synthetic analogue of AVP. DDAVP acts selectively at V2 receptors to increase urine concentration and decrease urine flow in a dose-dependent manner. It is also more resistant to degradation than is AVP and has a three to fourfold longer duration of action. DDAVP can be given by IV or SC injection, nasal inhalation, or orally by means of a tablet of melt. The doses required to control pituitary DI completely vary widely, depending on the patient and the route of administration. However, among adults, they usually range from 1-2 mg qd or bid by injection, 10-20 mg bid or tid by nasal spray, or 100-400 mg bid or tid orally. Reference : page 2278 Harrison's Principles of Internal Medicine 19th edition