Vasopressin

• Vasodilatory Shock (including Septic Shock):
  Adjunctive therapy to increase blood pressure in adult patients with vasodilatory shock refractory to conventional vasopressors such as norepinephrine.
• Diabetes Insipidus (Central):
  Treatment of central diabetes insipidus characterized by deficiency of endogenous antidiuretic hormone (ADH).
• Cardiac Arrest (Advanced Cardiovascular Life Support - ACLS):
  Alternative vasopressor agent during resuscitation for ventricular fibrillation, pulseless ventricular tachycardia, asystole, or pulseless electrical activity.
• Esophageal Variceal Bleeding:
  Used to reduce portal venous pressure and control acute variceal hemorrhage.
• Off-label Uses:
  Management of vasoplegic syndrome following cardiac surgery and prevention of hypotension during anesthesia.

• Route: Intravenous (IV) bolus or continuous infusion; intranasal administration for diabetes insipidus.
• Adults:
• Vasodilatory Shock: Continuous IV infusion at 0.01 to 0.04 units per minute.
• Cardiac Arrest: Single IV/IO bolus of 40 units during resuscitation (may replace first or second dose of epinephrine).
• Diabetes Insipidus (Intranasal): 10 to 40 micrograms per day divided into 2 to 4 doses.
• Pediatrics:
  Dose individualized; intranasal dosing for diabetes insipidus is lower than adults.
• Special Populations:
  Dose adjustment may be necessary in renal impairment. Careful monitoring of fluid balance and electrolytes is essential.

Vasopressin is a synthetic analog of antidiuretic hormone that acts on V1 receptors on vascular smooth muscle cells causing potent vasoconstriction, thereby increasing systemic vascular resistance and arterial blood pressure. It also stimulates V2 receptors in renal collecting ducts, enhancing water reabsorption which reduces urine output and concentrates urine. These combined effects restore vascular tone and fluid homeostasis, improving hemodynamics in shock and reducing polyuria in diabetes insipidus.

• Absorption: Rapid onset following IV administration; intranasal absorption variable but effective for central diabetes insipidus.
• Distribution: Widely distributed with moderate plasma protein binding.
• Metabolism: Metabolized primarily by proteolytic enzymes in the liver and kidneys.
• Elimination: Half-life ranges from 10 to 20 minutes; metabolites excreted mainly via renal route.

• Pregnancy: Category C. Animal studies suggest potential risk; no well-controlled human studies. Use only if benefits outweigh risks.
• Lactation: Excreted in breast milk in low concentrations. Use with caution; monitor infants if administered to nursing mothers.

• Vasopressor and antidiuretic hormone analog.

• Known hypersensitivity to vasopressin or any formulation component.
• Chronic nephritis or other conditions where vasoconstriction could be harmful.
• Patients with ischemic heart disease or severe peripheral vascular disease (relative contraindication; caution advised).

• Use caution in patients with coronary artery disease, peripheral vascular disease, or asthma.
• Risk of ischemic complications such as myocardial infarction, mesenteric ischemia, and limb ischemia due to vasoconstriction.
• Monitor for water intoxication and hyponatremia in diabetes insipidus therapy.
• Overdosage can lead to severe vasoconstriction and organ ischemia.
• Continuous monitoring of blood pressure, heart rate, fluid balance, and serum electrolytes is essential.

• Common: Headache, abdominal cramps, nausea, tremors, facial flushing.
• Cardiovascular: Bradycardia, hypertension, arrhythmias, chest pain, myocardial ischemia.
• Rare but Serious: Ischemic events including myocardial infarction and limb ischemia, anaphylaxis, hyponatremia.

• Potentiation of vasoconstrictive effects with other vasopressors or sympathomimetics.
• Increased risk of hyponatremia with concomitant use of drugs promoting water retention (e.g., carbamazepine, SSRIs).
• May reduce efficacy of vasodilators.
• No significant interactions via cytochrome P450 enzymes.

• Vasopressin is included as an adjunct vasopressor in current guidelines for septic shock management, particularly when norepinephrine alone is insufficient.
• ACLS guidelines allow vasopressin as an alternative to epinephrine in cardiac arrest but do not recommend routine use.
• Increased caution advised due to risks of ischemic complications; dosing recommendations have been refined to minimize adverse effects.

• Store refrigerated between 2°C and 8°C (36°F to 46°F).
• Protect from light.
• Do not freeze.
• After opening, use as per manufacturer’s instructions, generally within limited time to maintain potency.