Vasopressin
Vasopressin (Pitressin Synthetic)
Vasopressin
(vay-so- PRESS-in)
Pregnancy Category: C Pitressin Synthetic Pressyn (Rx)

Classification: Pituitary (antidiuretic) hormone

Action/Kinetics: Released from the anterior pituitary gland; regulates water conservation by promoting reabsorption of water by increasing the permeability of the collecting ducts in the kidney. Depending on the concentration, the hormone acts on both V ₁ and V ₂ receptors. Also causes vasoconstriction (pressor effect) of the splanchnic and portal vessels (and to a lesser extent of peripheral, cerebral, pulmonary, and coronary vessels). Also increases the smooth muscular activity of the bladder, GI tract, and uterus. IM, SC: Onset, variable; duration, 2-8 hr. t 1/2: 10-20 min. Effective plasma levels: 4.5-6 microunits.

Uses: Neurogenic (central) diabetes insipidus (ineffective when diabetes insipidus is of renal origin--nephrogenic diabetes insipidus). Relief of postoperative intestinal gaseous distention, to dispel gas shadows in abdominal roentgenography. Investigational: Bleeding esophageal varices.

Contraindications: Vascular disease, especially when involving coronary arteries; angina pectoris. Chronic nephritis until reasonable blood nitrogen levels are attained. Never give the tannate IV.

Special Concerns: Pediatric and geriatric clients have an increased risk of hyponatremia and water intoxication. Use caution during lactation and in the presence of asthma, epilepsy, migraine, CAD, and CHF.

Side Effects: GI: N&V;, increased intestinal activity (e.g., belching, cramps, urge to defecate), abdominal cramps, flatus. Miscellaneous: Facial pallor, tremor, sweating, allergic reactions vertigo, skin blanching, bronchoconstriction, anaphylaxis ``pounding'' in head, water intoxication (drowsiness, headache, coma, convulsions).
IV use of vasopressin may result in severe vasoconstriction; local tissue necrosis if extravasation occurs. IM use of tannate may cause pain and sterile abscesses at site of injection.

Overdose Management: Symptoms: Water intoxication. Treatment: Withdraw vasopressin until polyuria occurs. If water intoxication is serious, administration of mannitol (i.e., an osmotic diuretic), hypertonic dextrose, or urea alone (or with furosemide) is indicated.

Drug Interactions: Carbamazepine, chlorpropamide, or clofibrate may antidiuretic effects of vasopressin.

How Supplied: I njection: 20 U/mL.

Dosage
?IM, SC Diabetes insipidus.
Adults: 5-10 U b.i.d.-t.i.d.; pediatric: 2.5-10 U t.i.d.-q.i.d.
Abdominal distention.
Adults, initial: 5 U IM; then, 10 U IM q 3-4 hr; pediatric: individualize the dose (usual: 2.5-5 U).
Abdominal roentgenography.
IM, SC: 2 injections of 10 U each 2 hr and 1/2 hr before X rays are taken.
Esophageal varices.
Initial: 0.2 U/min IV or selective IA; then, 0.4 U/min if bleeding continues. The maximum recommended dose is 0.9 U/min.
?Intranasal (Using Injection Solution) Diabetes insipidus.
Individualize the dose using the injection solution on cotton pledgets, by nasal spray, or by dropper.