Vasopressin

Usage

• Vasopressin is prescribed for the treatment of diabetes insipidus, gastrointestinal bleeding, vasodilatory shock (especially in septic shock), and pulseless cardiac arrest. It is also used off-label for abdominal distension and abdominal roentgenography.
• Pharmacological Classification: Vasopressin is classified as an antidiuretic hormone, vasopressor and endocrine agent.
• Mechanism of Action: Vasopressin exerts its effects by binding to V1 receptors on vascular smooth muscle, causing vasoconstriction and increasing blood pressure. It also binds to V2 receptors in the kidneys, promoting water reabsorption and reducing urine output.

Alternate Names

• Alternate Names: Arginine vasopressin (AVP), antidiuretic hormone (ADH), argipressin.
• Brand Names: Pitressin, Vasostrict.

How It Works

• Pharmacodynamics: Vasopressin increases systemic vascular resistance, increases blood pressure and decreases heart rate. At higher doses, it stimulates V1 receptors in the gastrointestinal tract, leading to smooth muscle contraction. Stimulation of V3 receptors can cause the release of prolactin and ACTH. In the kidneys, it increases water reabsorption and concentrates urine.
• Pharmacokinetics:
  • Absorption: Rapid absorption following intravenous administration.
  • Metabolism: Metabolized in the liver and kidneys.
  • Elimination: Eliminated primarily through renal excretion.
• Mode of Action: Vasopressin binds to G protein-coupled receptors (V1, V2, and V3) on target cells. V1 receptor activation leads to vasoconstriction through the phospholipase C pathway. V2 receptor activation stimulates adenylyl cyclase, leading to increased cAMP and water reabsorption in the kidneys.
• Receptor Binding: Binds to V1, V2, and V3 receptors.
• Elimination Pathways: Primarily renal excretion, with some hepatic metabolism.

Dosage

Standard Dosage

Adults:

• Vasodilatory Shock: Initial dose: 0.01-0.04 units/min IV infusion; titrate to effect. Maximum rate: up to 0.1 units/min.
• Diabetes Insipidus: 5-20 units IM/SC every 4-8 hours as needed.

Children:

• Pediatric dosing is weight-based and should be determined based on the specific indication and clinical status. Consult pediatric dosing guidelines.

Special Cases:

• Elderly Patients: Start with a lower dose and titrate cautiously, monitoring closely for side effects.
• Patients with Renal Impairment: Dose adjustment may be necessary.
• Patients with Hepatic Dysfunction: Dose adjustment may be necessary.
• Patients with Comorbid Conditions: Close monitoring is recommended.

Clinical Use Cases

• Intubation: May be used as a vasopressor to support blood pressure during intubation.
• Surgical Procedures: May be used to control bleeding during surgery, especially in the gastrointestinal tract.
• Mechanical Ventilation: May be used to manage hypotension in mechanically ventilated patients.
• Intensive Care Unit (ICU) Use: Commonly used to manage vasodilatory shock and maintain blood pressure in critically ill patients.
• Emergency Situations:
  • Cardiac Arrest: 40 units IV/IO push as a single dose, may replace the first or second dose of epinephrine.
  • Septic Shock: Initial dose of 0.01-0.03 units/min IV infusion, titrate by 0.005 units/min at 10-15 minute intervals.

Dosage Adjustments:

• Dose adjustments are based on patient response, blood pressure, and other clinical factors.
• Renal and hepatic impairment may necessitate dosage modifications.

Side Effects

Common Side Effects:

• Nausea, vomiting, abdominal cramps, headache, tremor, pallor.

Rare but Serious Side Effects:

• Myocardial ischemia, arrhythmias, hyponatremia, water intoxication.

Long-Term Effects:

• Chronic complications are rare but can include hyponatremia and fluid imbalance with prolonged use.

Adverse Drug Reactions (ADR):

• Severe hyponatremia, myocardial infarction, arrhythmias, anaphylaxis.

Contraindications

• Hypersensitivity to vasopressin, chronic nephritis, vascular disease, angina pectoris.

Drug Interactions

• Carbamazepine, chlorpropamide, clofibrate, fludrocortisone, urea, tricyclic antidepressants: May potentiate the antidiuretic effect of vasopressin.
• Demeclocycline, lithium, norepinephrine, heparin: May diminish the antidiuretic effect of vasopressin.
• Ganglionic blocking agents may produce profound hypotension.

Pregnancy and Breastfeeding

• Pregnancy Safety Category: Consult pregnancy-specific guidelines.
• Vasopressin can cause uterine contractions and should be used with caution during pregnancy.
• It is unknown if vasopressin is excreted in breast milk. Use with caution during breastfeeding.

Drug Profile Summary

• Mechanism of Action: Binds to V1 and V2 receptors, causing vasoconstriction and water reabsorption.
• Side Effects: Nausea, vomiting, abdominal cramps, myocardial ischemia, hyponatremia.
• Contraindications: Hypersensitivity, chronic nephritis, vascular disease, angina pectoris.
• Drug Interactions: See above.
• Pregnancy & Breastfeeding: Consult specific guidelines for use during pregnancy and breastfeeding.
• Dosage: See above.
• Monitoring Parameters: Blood pressure, heart rate, urine output, serum electrolytes.

Popular Combinations

• Norepinephrine and vasopressin are commonly used in combination for the treatment of septic shock.

Precautions

• Use with caution in patients with cardiovascular disease, renal impairment, and asthma.
• Monitor electrolytes, especially sodium.
• Avoid extravasation during IV administration.

FAQs (Frequently Asked Questions)

Q1: What is the recommended dosage for Vasopressin?

A: Dosage varies depending on indication. See detailed dosage guidelines above.

Q2: How should Vasopressin be administered?

A: Vasopressin can be administered intravenously, intramuscularly, or subcutaneously. For IV administration, dilute as per guidelines and administer via an infusion pump.

Q3: What are the common side effects of Vasopressin?

A: Common side effects include nausea, vomiting, abdominal cramps, headache, blanching of the skin.

Q4: What are the serious side effects of Vasopressin?

A: Serious side effects can include myocardial ischemia, arrhythmias, and water intoxication.

Q5: What are the contraindications for using Vasopressin?

A: Contraindications include hypersensitivity to vasopressin, chronic nephritis, and severe vascular disease.

Q6: How does Vasopressin interact with other drugs?

A: Vasopressin can interact with numerous medications, including carbamazepine, chlorpropamide, lithium, norepinephrine, and tricyclic antidepressants. Consult drug interaction resources for details.

Q7: Can Vasopressin be used during pregnancy and breastfeeding?

A: Use with caution during pregnancy and breastfeeding. Consult pregnancy-specific guidelines.

Q8: What monitoring parameters should be considered while administering Vasopressin?

A: Monitor blood pressure, heart rate, urine output, and serum electrolytes.

Q9: What is the difference between the V1 and V2 receptors for Vasopressin?

A: V1 receptors are located on vascular smooth muscle and mediate vasoconstriction, while V2 receptors are located in the kidneys and mediate water reabsorption.

Q10: What is the role of Vasopressin in septic shock?

A: Vasopressin is used as a vasopressor in septic shock to increase blood pressure and improve tissue perfusion, often in combination with norepinephrine. It may reduce the need for high doses of norepinephrine, potentially mitigating some of its adverse effects.

This information is current as of February 17, 2025. Always consult up-to-date resources and guidelines for the most current information.