Vasopressin

Indications

Vasopressin is a hospital medicine used mainly to raise dangerously low blood pressure in adults with vasodilatory shock (such as septic shock) when fluids and other blood pressure medicines (catecholamines) are not enough. It has also been used for central diabetes insipidus and, in some settings, to help control bleeding from enlarged veins in the food pipe (oesophageal varices).

How It Works

Vasopressin is a man-made form of antidiuretic hormone, a natural hormone made by the pituitary gland. It acts on V1 receptors in blood vessel walls, causing the vessels to narrow, which raises blood pressure. It also acts on V2 receptors in the kidneys to help the body keep water and make more concentrated urine.

Dosage and Administration

Vasopressin is given by a doctor or nurse in a hospital, usually in an intensive care unit, as a continuous infusion into a vein through a pump. The dose is adjusted carefully according to blood pressure and the patient's condition and is as prescribed. Blood pressure, heart rhythm, fluid balance and blood sodium are monitored closely.

Interactions

• Other medicines that raise blood pressure (such as Noradrenaline) add to its effect; doses are adjusted together.
• Carbamazepine, Chlorpropamide, Clofibrate and Fludrocortisone may increase its water-retaining effect.
• Lithium, Demeclocycline and Heparin may reduce its kidney effect.
• Medicines that slow the heart can add to a slow heart rate.

Contraindications

• Allergy to Vasopressin or to any ingredient, such as chlorobutanol in some products.
• Use with great care, or avoid, in people with serious coronary artery disease, because narrowing of blood vessels can reduce blood flow to the heart.

Side Effects

Possible side effects include reduced blood flow to the fingers, toes, skin, gut or heart (which may cause pale or cold extremities, abdominal pain or chest pain), slow or irregular heartbeat, low blood sodium from water retention, headache, nausea, abdominal cramps and skin reactions at the infusion site.

Tell the nurse or doctor at once if the patient has chest pain, severe abdominal pain, fingers or toes turning blue or very pale, confusion, a seizure, or signs of an allergic reaction such as swelling or difficulty breathing.

Pregnancy and Lactation

Vasopressin may cause contractions of the womb. In pregnancy it is used only when the benefit clearly outweighs the risk, under specialist care. It is not known whether meaningful amounts pass into breast milk; the treating team will advise on breastfeeding.

Precautions and Warnings

• Given only in hospital with close monitoring.
• Use with care in heart disease, epilepsy, migraine, asthma and kidney disease.
• Fluid intake and blood sodium are watched to avoid water intoxication.
• The infusion is reduced gradually rather than stopped suddenly.

Overdose

Too much Vasopressin can cause very high blood pressure, reduced blood flow to organs and limbs, slow heartbeat and water intoxication (low sodium with confusion or seizures). The infusion is stopped or reduced and supportive treatment is given in hospital.

Therapeutic Class

Vasopressor; antidiuretic hormone analogue.

Storage

Store as directed on the pack, usually in a refrigerator at 2 to 8°C, do not freeze. It is stored and prepared by hospital staff.