Vasopressin (Pitressin®, DDAVP)

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Vasopressin (Pitressin®, DDAVP)

By: Dr. Nicholas Dodman

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Overview

Vasopressin is a hormone formed primarily in the supraoptic nuclei of the hypothalamus in the brain. It is transported from there, in combination with neurophysin, to the posterior pituitary gland where it is stored in nerve endings prior to its release into the blood stream.

Vasopressin acts on the kidneys, specifically the renal tubular epithelium, where it promotes reabsorption of water and causes vasoconstriction throughout the vascular bed.

Vasopressin also increases gastrointestinal motility and tone.

Vasopressin temporarily reverses central (neurogenic) diabetes insipidus (DI) though it is ineffective in nephrogenic DI.

For this reason, it is used to differentiate the two conditions though there are also therapeutic indications.

A long-acting preparation of vasopressin, vasopressin tannate in oil, used to be used for treatment of DI. This preparation is no longer available so clinicians are now using the deamino analog of vasopressin (DDAVP) for this therapy.

Vasopressin is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.

This drug is not approved for use in animals by the Food and Drug Administration but it is prescribed legally by veterinarians as an extra-label drug.

Brand Names and Other Names

This drug is registered for use in humans only.

Human formulations: Pitressin® (Monarch) and generic equivalents.

Veterinary formulations: None

Uses of Vasopressin

Vasopressin is used for the diagnosis of diabetes insipidus.

Precautions and Side Effects

While generally safe and effective when prescribed by a veterinarian, vasopressin can cause side effects in some animals.

Vasopressin should not be used in animals with known hypersensitivity or allergy to it or its components.

Also, unless employed with caution, it may cause water intoxication [with clinical signs ranging from drowsiness to coma and convulsions].

Injections outside of the blood vessel can be very irritating and cause tissue necrosis.

Chronic nephritis with elevated blood nitrogen levels constitutes a contraindication to the use of vasopressin. BUN levels should be brought into a reasonable range first.

Epileptic patients and those with heart failure pose may have their condition exacerbated by vasopressin because of increased water retention.

Adverse reactions to vasopressin include cardiac arrhythmias, heart failure, tremor, ataxia, urticaria, abdominal pain, passage of gas, anaphylaxis, and bronchoconstriction.

It is recommended to monitor the electrocardiogram (ECG) and fluid/electrolyte status during prolonged administration of vasopressin.

Drug Interactions

Vasopressin may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with vasopressin. Such interactions may include:

The following drugs potentiate the antidiuretic effect of vasopressin: carbamazepine, chlorpropamide, urea, fludrocortisone, and tricyclic antidepressants (e.g. clomipramine).

The following drugs may reduce the antidiuretic effect of vasopressin: demeclocycline, norepinephrine, lithium, and heparin.

How Vasopressin is Supplied

The injectable forms include 20 pressor units/mL concentrations available in 0.5 and 1 mL amps and 10 mL vials.

Dosing Information

Medication should never be administered without first consulting your veterinarian.

The dosage prescribed may vary depending on the reason for prescribing.

In dogs, vasopressin may be used as follows for diagnosis of neurogenic DI: Following a water deprivation test, the dog's bladder is emptied and an IV infusion of dilute vasopressin is started while periodically (e.g. @ 30, 60, 90 minutes) monitoring urine specific gravity (bladder must be emptied between measurements). If urine concentration remains low, nephrogenic DI is the most likely diagnosis.

In cats, vasopressin may be used as follows for diagnosis of neurogenic DI: Following a water deprivation test, vasopressin is administered by intramuscular injection. The urine concentration is monitoring at 30, 60, 120 minutes. Inability of the cat to concentrate urine following administration of vasopressin is indicative of neurogenic DI.