VASOPRESSIN

Clinical safety rating: safe

Animal studies have demonstrated safety

How it works

Vasopressin is an antidiuretic hormone that acts on V1 receptors (vascular smooth muscle) to cause vasoconstriction and on V2 receptors (renal collecting ducts) to increase water reabsorption. It also stimulates V1b receptors in the pituitary, modulating ACTH release.

What the body does with it

Metabolism	Primarily hepatic and renal metabolism via peptide hydrolases; small amount excreted unchanged in urine.
Excretion	Primarily hepatic and renal metabolism; <5% excreted unchanged in urine. Biliary/fecal routes minimal.
Half-life	Terminal elimination half-life: IV 10–20 minutes; subcutaneous/intramuscular 30–40 minutes. Clinically, duration of antidiuretic effect is 2–8 hours.
Protein binding	Approximately 30%, primarily to albumin and vasopressin-binding protein (neurophysin).
Volume of Distribution	Approximately 0.1–0.2 L/kg, indicating distribution primarily in extracellular fluid. Clinical significance: low Vd reflects limited tissue penetration.
Bioavailability	Intranasal: 10–20%; subcutaneous/intramuscular: ~85% compared to IV. Oral bioavailability negligible (<1%).
Onset of Action	IV: Immediate (1–2 minutes); subcutaneous/intramuscular: 15–30 minutes; intranasal: 30–60 minutes.
Duration of Action	IV: 30–60 minutes; subcutaneous/intramuscular: 2–8 hours; intranasal: 6–12 hours. Effects on water reabsorption persist longer than vasopressor effects.

Classification & Brands

Dosing & administration

IV: 0.01-0.04 units/min for vasodilatory shock; titrate to effect.

Dosage form	SOLUTION
Renal impairment	No adjustment required for decreased GFR; monitor urine output and electrolytes.
Liver impairment	Child-Pugh A-B: No adjustment; Child-Pugh C: Use with caution due to risk of hyponatremia and fluid overload.
Pediatric use	IV: 0.0003-0.002 units/kg/min for vasodilatory shock; titrate to effect.
Geriatric use	Start at low end of dosing range (0.01 units/min) due to increased sensitivity and risk of hyponatremia.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Other drugs that can cause water intoxication may have additive effects Can cause hyponatremia and tissue necrosis with extravasation.

Breastfeeding

Vasopressin is not likely to be excreted into breast milk in significant amounts due to its high molecular weight and rapid degradation. The milk-to-plasma ratio is unknown. Caution is advised; use only if clearly needed and monitor infant for adverse effects.

Teratogenic Risk

Vasopressin is classified as FDA Pregnancy Category C. Animal reproduction studies have not been conducted. In humans, vasopressin is used in critical care settings and limited data are available. First trimester: No evidence of teratogenicity reported, but risk cannot be excluded. Second and third trimesters: Vasopressin may cause uterine contractions and reduced placental perfusion; use only if clearly needed for maternal indications.

Warnings & precautions

■ FDA Black Box Warning

Ischemic events: Vasopressin can cause severe vasoconstriction leading to ischemia of the heart, brain, and other organs. Patients with vascular disease are at higher risk.

Side Effect Profile

Common Effects	vasodilatory shock
Serious Effects

Absolute Contraindications

Hypersensitivity to vasopressin or its components; caution in patients with pre-existing ischemic heart disease or peripheral vascular disease.

Clinical Precautions

Precautions

Monitor for hyponatremia and fluid overload; use with caution in patients with coronary artery disease, hypertension, and renal impairment; can cause gangrene with extravasation; may cause anaphylaxis.

Clinical Tips & Counseling

Drug interactions

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