Vasopressin

# vasopressin ## Overview - **Classification**: Antidiuretic hormone analog, Vasopressor. - **Mechanism**: Acts on V1 receptors in vascular smooth muscle to cause vasoconstriction; acts on V2 receptors in renal tubules to increase water reabsorption. ## Primary Indications 1. **Septic Shock**: Adjunctive therapy to catecholamines to increase mean arterial pressure. 2. **Cardiac Arrest**: Alternative to epinephrine in pulseless VF/VT (though less commonly used per current ACLS). 3. **Diabetes Insipidus**: Treatment of central diabetes insipidus. 4. **Variceal Hemorrhage**: Off-label use to reduce portal pressure in GI bleeding. ## Adult Dosing ### Standard Dosing **Septic Shock (Refractory)** - **Dose**: **0.01-0.07 units/min** (typical initial **0.03 units/min**) - **Frequency**: Continuous IV infusion - **Route**: Intravenous (central line preferred) - **Special Considerations**: Administer with norepinephrine; typically not titrated based on BP. **Cardiac Arrest (Pulseless VF/VT)** - **Dose**: **40 units** - **Frequency**: Single dose - **Route**: IV/IO - **Special Considerations**: Current ACLS guidelines no longer routinely recommend vasopressin; epinephrine is preferred. **Diabetes Insipidus (Central)** - **Dose**: **5-10 units** - **Frequency**: Subcutaneous or Intramuscular every 6-8 hours PRN - **Route**: SC/IM - **Duration**: Adjust based on urine output and serum osmolality. **Variceal Hemorrhage (Off-label)** - **Dose**: **0.2 units/min** initial, then titrate up to **0.8 units/min** - **Frequency**: Continuous IV infusion - **Route**: Intravenous - **Special Considerations**: Administer with intravenous nitroglycerin to reduce coronary vasoconstriction. ### Dose Adjustments - **Renal Impairment**: No specific dose adjustments recommended for acute use. Monitor fluid balance and electrolytes closely. - **Hepatic Impairment**: No specific dose adjustments recommended. Monitor for accumulation and adverse effects. - **Elderly Patients**: Use caution. Monitor closely for cardiovascular effects, fluid overload, and hyponatremia. ## Pediatric Dosing ### Neonates (0-28 days) - **Indication**: Refractory Septic Shock - **Dose**: Start **0.0003 units/kg/min** continuous IV infusion. - **Frequency**: Continuous - **Maximum**: Up to **0.002 units/kg/min**. Higher doses up to **0.005 units/kg/min** with extreme caution. - **Special Notes**: Use is off-label; reserved for refractory shock. Monitor for signs of ischemia (e.g., gut, limb). ### Infants (1-12 months) - **Indication**: Refractory Septic Shock - **Dose**: Start **0.0003 units/kg/min** continuous IV infusion. - **Frequency**: Continuous - **Maximum**: Up to **0.002 units/kg/min**. Higher doses up to **0.005 units/kg/min** with extreme caution. ### Children (1-12 years) - **Indication**: Refractory Septic Shock - **Dose**: Start **0.0003 units/kg/min** continuous IV infusion. - **Frequency**: Continuous - **Maximum**: Up to **0.002 units/kg/min** or **0.07 units/min** (adult max), whichever is lower. Higher doses up to **0.005 units/kg/min** with extreme caution. ### Adolescents (13-18 years) - **Indication**: Refractory Septic Shock - **Dose**: Approach adult dosing. Start **0.01 units/min** continuous IV infusion. - **Frequency**: Continuous - **Maximum**: Up to **0.07 units/min**. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to vasopressin or its components. - **Relative**: Chronic nephritis with nitrogen retention. ### Common Adverse Effects - **Very Common (>10%)**: Fluid retention, hyponatremia (especially with DI use). - **Common (1-10%)**: Ischemic events (myocardial, mesenteric, peripheral), abdominal cramps, nausea, tremor, pallor. - **Serious but Rare**: Myocardial infarction, angina, bradycardia, stroke, severe hyponatremia leading to seizures, anaphylaxis. ### Key Drug Interactions - **Catecholamines (e.g., Epinephrine, Norepinephrine)**: May have additive pressor effects. Monitor blood pressure closely. - **Carbamazepine, Chlorpropamide, TCAs, SSRIs, NSAIDs**: May potentiate vasopressin's antidiuretic effect, increasing hyponatremia risk. - **Lithium, Demeclocycline, Ethanol**: May reduce vasopressin's antidiuretic effect. ## Monitoring & Follow-up - **Before Treatment**: Baseline BP, HR, ECG, serum electrolytes (especially Na+), fluid status. - **During Treatment**: Continuous BP, HR, ECG. Monitor urine output, serum electrolytes (Na+), central venous pressure (CVP), cardiac output, and peripheral perfusion. - **Clinical Signs**: Watch for signs of myocardial, mesenteric, or peripheral ischemia. Monitor for fluid overload and hyponatremia. ## Clinical Pearls - 💡 **Tip 1**: Vasopressin is often used as a **catecholamine-sparing agent** in septic shock, allowing for lower doses of other vasopressors. - 💡 **Tip 2**: For septic shock, vasopressin is usually initiated as a **fixed dose** and not titrated based on BP, unlike catecholamines. - 💡 **Tip 3**: Requires **dilution prior to administration** and should be infused via a central venous catheter if possible to minimize extravasation risk. - 💡 **Tip 4**: Has minimal direct inotropic/chronotropic effects compared to adrenergic vasopressors. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.