Vasopressor · Hormone
Vasopressin (Vasostrict)
Also called Vasostrict
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Indications
- Vasodilatory shock (septic or after cardiac surgery) despite fluids and catecholamines: fixed-dose add-on to norepinephrine
- RV failure or pulmonary hypertension, as a pressor that spares PVR (off-label)
- Refractory hypotension under anesthesia in patients on ACE inhibitors or ARBs (off-label)
- Brain-dead organ donors: diabetes insipidus and vasoplegia (off-label)
- Central diabetes insipidus (off-label; desmopressin is usual)
Dosing
Vasopressin drip card and mL/h converterStart: 0.03 units/min, usually fixed (some start at 0.01)
Mechanism of action
Vasopressin (antidiuretic hormone) is a posterior pituitary nonapeptide. Vascular V1a receptors couple to Gq/11: IP3 releases calcium and the vessel constricts; vasopressin also closes K-ATP channels that acidosis and low ATP open in septic shock, restoring catecholamine responsiveness. Collecting duct V2 receptors couple to Gs: cAMP inserts aquaporin-2 water channels (antidiuresis). Septic shock depletes stored vasopressin, so a low fixed dose works as hormone replacement.
Pharmacology
- Cardiovascular: raises SVR and MAP and spares norepinephrine; heart rate and cardiac output fall slightly; little PVR effect at low doses
- Cardiovascular: patchy constriction, strongest in skin, muscle and gut, with coronary constriction at higher doses
- Renal: V2 concentrates urine and can lower sodium; efferent more than afferent constriction may support GFR (VANISH: less RRT)
- Hematologic: V2 releases von Willebrand factor and factor VIII; V1 aids platelet aggregation
- Other: pituitary V1b receptors release ACTH; high doses can contract the uterus (label)
Pharmacokinetics
| Onset | Minutes IV; peak pressor effect within 15 min (label) |
|---|---|
| Duration | Fades within 20 min of stopping (label) |
| Half-life | 10 min or less (label) |
| Distribution | Vd about 140 mL/kg (label) |
| Metabolism | Liver and kidney peptidases (serine protease, carboxypeptidase, disulfide oxidoreductase) |
| Clearance | 9–25 mL/min/kg in vasodilatory shock (label) |
| Elimination | About 6% unchanged in urine |
| Pregnancy | Placental vasopressinase raises clearance 4–5-fold by the third trimester; doses may need to rise (label) |
Chemistry
- Nonapeptide Cys-Tyr-Phe-Gln-Asn-Cys-Pro-Arg-Gly-NH₂: a Cys1–Cys6 disulfide bridge closes a six-residue ring, leaving a three-residue tail ending in glycinamide; MW 1084
- Arginine at position 8 makes it arginine vasopressin, the human hormone (made synthetically); oxytocin differs only at positions 3 and 8
- Analogues: desmopressin is V2-selective (no pressor effect); terlipressin is a V1-selective lysine vasopressin prodrug
- Dosed in units: 20 units/mL vials (the multidose vial has chlorobutanol 0.5%) and premixed 20 or 40 units/100 mL saline; pH about 3.5–4; store refrigerated
Adverse effects and cautions
In the one-pagers
- Vasopressors and InotropesReceptors and effects: Vasopressin: V1 (V2 in kidney): ↔ or ↓ / ↔ / ↑↑
- Toxidromes and AntidotesCardiotoxic drugs: Local anesthetics: 20% lipid 1.5 mL/kg (up to 100 mL), then infusion: Small epinephrine doses; no vasopressin
- ACLS Algorithms in BriefCPR quality, shocks and drugs: Not routine in arrest: calcium, bicarbonate, magnesium, vasopressin, high-dose epinephrine, pacing. Hyperkalemic arrest: calcium and bicarbonate may be considered (2025: benefit unproven).
- Obstetric EmergenciesSepsis and venous thromboembolism: SMFM #47: antibiotics within 1 h, cultures, lactate, source control, 1–2 L of crystalloid, norepinephrine first, and no delivery for sepsis alone. Vasopressin at a fixed 0.03 units/min is a reasonable second pressor, and stress-dose hydrocortisone is held while antenatal steroids are given (Bauer and Pacheco 2025).
- Prehospital SepsisVasopressors in transport: Second agent: Vasopressin 0.03 units/min, fixed, as norepinephrine climbs
- Pulmonary EmbolismSupporting the failing RV: Norepinephrine first: keeps aortic above RV pressure; vasopressin second
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Sources
- FDA label: Vasostrict (2016)
- FDA label: vasopressin in sodium chloride, Baxter (2024)
- VANISH (Gordon, JAMA 2016)
For education and exam preparation only. Follow your institution’s protocols. Typical adult values for study. Follow your local protocols and medical direction.