IV Dilution &
Medication Reference

Vasopressin (Pitressin ®)

Usual Diluents

Standard Dilutions [Amount of drug] [Infusion volume] [Infusion rate]

ICU - Vasodilatory shock/septic shock
[40 units ] [100 ml ] [0.01 - 0.03 units/minute]
Rates:
0.01 units/minute = 1.5 ml/hr
0.02 units/minute = 3 ml/hr
0.03 units/minute = 4.5 ml/hr

Doses greater than 0.04 units/min may lead to cardiac arrest. Rapid rebound hypotension is a common problem after treatment with vasopressin is stopped. Ideally, vasopressin should be
tapered slowly by 0.01 unit/minute increments before discontinuing. Background info.

Stability / Miscellaneous

"Antidiuretic hormone"

Dosing (adults):
Diabetes insipidus: 5-10u IM/SC 2 to 4 times/day as needed.
Abdominal distention: 5 units IM stat, followed by 10 units q3-4h.

Vasodilatory shock/septic shock: Vasopressin may be used in patients with refractory shock despite adequate fluid resuscitation and the use of high-dose conventional catecholamines such as norepinephrine and dopamine, however, further studies are needed to determine its exact place in therapy. Current evidence does not support the use of vasopressin as a replacement for norepinephrine or dopamine as a first-line agent. The recommended infusion rate for vasopressin in the treatment of shock in adults is 0.01- 0.03 units/min. This dosage range is reported to be effective in about 85% of patients with norepinephrine resistant hypotension. Doses greater than 0.04 units/min may lead to cardiac arrest.

Bleeding esophageal varices and other types of upper GI bleeds:
initially 0.2 u/min, then increase each hour by 0.2 u/min until the hemorrhage is controlled. Doses as high as 2 u/min may be tolerated, but a more prudent dosage limit is 1 u/min. After 12 hours of control of the hemorrhage the dose of vasopressin may be decreased by 50%, then may discontinue in the next 12-24 hrs. Intravenous nitroglycerin should be administered concomitantly to control side effects.

MOA: ADH and pressor activity. Portal blood pressure is significantly decreased. A decrease in porto-systemic collateral flow and an increase in the muscular tone of the lower esophagus reduces blood flow to esophageal varices. The smooth muscle of the GI tract is also effected by large doses and peristaltic activity of the bowel and smooth muscles of the uterus are stimulated.

INDICATIONS
Vasopressin is indicated for prevention and treatment of postoperative abdominal distention, in abdominal roentgenography to dispel interfering gas shadows, and in diabetes insipidus.

DOSAGE AND ADMINISTRATION
Vasopressin may be administered intramuscularly or subcutaneously.

Ten units of vasopressin (0.5mL) will usually elicit full physiologic response in adult patients: 5units will be adequate in many cases. Vasopressin should be given intramuscularly at three-or four-hour intervals as needed. The dosage should be proportionately reduced for children.(For an additional discussion of dosage, consult the sections below.)

When determining the dose of vasopressin for a given case, the following should be kept in mind.

It is particularly desirable to give a dose not much larger than is just sufficient to elicit the desired physiologic response. Excessive doses may cause undesirable side effects - blanching of the skin, abdominal cramps, nausea, which, though not serious, may be alarming to the patient. Spontaneous recovery from such side effects occurs in a few minutes. It has been found that one or two glasses of water given at the time vasopressin is administered reduce such symptoms.

Abdominal Distention: In the average postoperative adult patient, give 5 units (0.25 mL) initially, increase to 10 units (0.5mL) at subsequent injections if necessary. It is recommended that vasopressin be given intramuscularly and that injections be repeated at three-or four-hour intervals as required. Dosage to be reduced proportionately for children.

Vasopressin used in this manner will frequently prevent or relieve postoperative distension. These recommendations apply also to distention complicating pneumonia or other acute toxemias.

Abdominal Roentgenography: For the average case, two injections of 10 units each (0.5 mL) are suggested . These should be given two hours and one-half hour, respectively, before films are exposed. Many roentgenologists advise giving an enema prior to the first dose of vasopressin.

Diabetes Insipidus: Vasopressin may be given by injection or administered intranasally on cotton pledgets, by nasal spray, or by dropper. The dose by injection is 5 to 10 units (0.25 to 0.5mL) repeated two or three times daily as needed. When vasopressin is administered intranasally by spray or on pledgets, the dosage and interval between treatments must be determined for each patient.

Parenteral drug products should be inspected visually for particulate matter and discoloration prior to use, whenever solution and container permit.

HOW SUPPLIED
Vasopressin Injection, USP 20units/L is supplied as follows:

For intramuscular or subcutaneous use:

10 units per 0.5 mL multiple dose vial Boxes of 25
20 units per 1mL multiple dose vial Boxes of 25
200 units per 10 mL multiple dose vial Boxes of 10

Store at controlled room temperature 15°-30° C (59°-86° F).

Source: [package insert]