Section II. ANTIDIURETIC AGENTS
The antidiuretic hormone has been discussed in Lesson 6 of this subcourse. As
you will remember, it is a hormone secreted by the pituitary gland. The antidiuretic
hormone (ADH) acts on the distal tubule and collecting ducts to increase water
reabsorption (and thus to decrease urine output). The agents discussed below are
those that work in a manner opposite the diuretics. This process is called antidiuresis.
Antidiuresis is the suppression of urinary secretion. Consequently, an antidiuretic is an
agent that suppresses urine formation as well as the rate of urine formation.
8-6. MECHANISM OF ACTION OF ANTIDIURETICS
Antidiuretics work by increasing the reabsorption of water at the distal tubule and
collecting ducts without significantly modifying the rate of glomerular filtration.
8-7. EXAMPLES OF ANTIDIURETIC AGENTS
Two examples of antidiuretic agents are presented below.
a. Vasopressin (Pitressin). This agent is used for the control or prevention of
the symptoms and complications of diabetes insipidus. For vasopressin injection, the
dose is 5 to 10 units (0.25 to 0.5 milliliters) by intramuscular or subcutaneous injection
as required (usually every 2 to 3 hours as needed). The side effects associated with
this product include abdominal cramps, fluid retention, and increased blood pressure. It
is dispensed for hospital use only and should never be administered intravenously. This
drug is available as a solution containing 20 pressor units per milliliter.
b. Lypressin (Diapid). This agent is also used for the control or prevention of
the symptoms and complications of diabetes insipidus. The usual dosage of this drug is
1 to 2 sprays applied to each nostril four times daily. The side effects associated with
lypressin are abdominal cramps, nasal congestion, fluid retention, and increased bowel
movements. Lypressin is useful in patients suffering from diabetes insipidus who have
become unresponsive to other therapy or who experience allergic or other undesirable
reactions to antidiuretic hormone of animal origin. The product has to be kept
refrigerated. This product has an expiration date of 36 months. It is available as a
nasal spray, 0.185 milligrams of lypressin per milliliter of solution (equivalent to 50 units