VASOPRESSIN
Clinical safety rating: safe
Animal studies have demonstrated safety
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.
| 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. |
| Molecular Weight | 1084.25 |
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. |
| 1st trimester | Associated with decreased uterine blood flow and potential fetal hypoxia; use only if benefit outweighs risk (e.g., hemorrhagic shock). |
| 2nd trimester | Same as T1; may cause uterine contractions and preterm labor. |
| 3rd trimester | Same as T2; risk of hypertension and water intoxication in mother and fetus. |
Clinical note
Other drugs that can cause water intoxication may have additive effects Can cause hyponatremia and tissue necrosis with extravasation.
| Placental transfer | Crosses placenta; limited data, but vasopressin is a peptide that may be degraded by placental enzymes. |
| Breastfeeding | Excreted in breast milk in small amounts; unlikely to affect nursing infant due to rapid degradation in GI tract. |
| Lactation Rating |
■ 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.
| Common Effects | vasodilatory shock |
| Serious Effects |
Hypersensitivity to vasopressin or any componentChronic nephritis with nitrogen retentionCoronary artery disease (avoid in ischemic heart disease)Peripheral vascular diseaseAngina pectoris
| 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. |
| Food/Dietary | No known food interactions. However, fluid intake may need to be monitored, especially in patients with hyponatremia or fluid overload. Alcohol may worsen the underlying condition (e.g., variceal bleeding). |
Loading safety data…
| L1 – Safe |
| 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. |
| Fetal Monitoring | Monitor maternal blood pressure, heart rate, urine output, serum sodium, and fluid status. Fetal heart rate should be monitored for signs of distress if used during pregnancy. Assess for signs of uterine hyperstimulation. |
| Fertility Effects | No specific data on fertility effects in humans. Animal studies have not reported adverse effects on fertility. Vasopressin is used in critical care settings and unlikely to be used routinely in women of reproductive potential for non-life-threatening conditions. |
| Clinical Pearls | Vasopressin is primarily used in vasodilatory shock (e.g., septic shock) as a second-line agent after norepinephrine. It is also used for diabetes insipidus and as a hemostatic agent in variceal bleeding. Do not use in patients with coronary artery disease due to risk of myocardial ischemia. Monitor for hyponatremia and fluid overload. For cardiac arrest, IV/IO dose is 40 units as a single dose, replacing first or second dose of epinephrine. |
| Patient Advice | This medication is given to raise blood pressure in certain types of shock. · You may experience paleness, nausea, or abdominal cramps. · Report any chest pain, difficulty breathing, or severe headache immediately. · For diabetes insipidus, take exactly as prescribed; do not stop suddenly. · Avoid alcohol and limit fluid intake if advised by your doctor. |