Chapter 5  ·  Module 2  ·  Visual Summary

Catecholamine Agonists

Epinephrine · Norepinephrine · Dopamine · Dobutamine

Drug Profiles at a Glance

Epinephrine

Full Alpha + Beta Agonist

ReceptorsAlpha-1, Alpha-2, Beta-1, Beta-2, Beta-3
Key usesAnaphylaxis (first-line, intramuscular thigh), cardiac arrest (1 mg intravenous), local anesthetic adjuvant
CautionContraindicated with local anesthetics at end-artery sites (digits, penis, nose tip)

Norepinephrine

Predominant Alpha + Beta-1

ReceptorsAlpha-1, Alpha-2, Beta-1 (minimal Beta-2)
Key usesFirst-line vasopressor for septic shock; neurogenic shock
CautionExtravasation → tissue necrosis; treat with phentolamine infiltration. Central venous access preferred.

Dopamine

Dose-Dependent Receptor Profile

Low doseD1 → renal vasodilation (does NOT protect kidneys)
Mod doseBeta-1 → increased cardiac output
High doseAlpha-1 → vasoconstriction; high arrhythmia risk
NowNot first-line for shock; norepinephrine preferred

Dobutamine

Selective Beta-1 Inotrope

ReceptorsBeta-1 dominant; mild Beta-2 (afterload reduction)
Key usesCardiogenic shock (+ norepinephrine); acute decompensated heart failure; dobutamine stress echocardiography
CautionDoes not raise mean arterial pressure reliably; tachyphylaxis after 72 hours

High-Risk Drug Interactions

Interacting Drug Risk Level Mechanism and Effect Management
Monoamine oxidase inhibitors DANGEROUS Irreversible enzyme inhibition → catecholamine accumulation → hypertensive crisis. Effect persists 2 weeks after stopping. Avoid catecholamines for 2 weeks. Use phenylephrine if vasopressor required.
Tricyclic antidepressants CAUTION Norepinephrine transporter blockade → prolonged catecholamine effect. Indirect agents less effective. Reduce direct catecholamine doses; monitor closely.
Non-selective beta-blockers (anaphylaxis) DANGEROUS Beta-2 blockade → unopposed alpha-1 → paradoxical hypertension + persistent bronchospasm despite epinephrine. Glucagon 1–2 mg intravenous (bypasses blocked receptors via Gs). Add ipratropium.
Cocaine intoxication DANGEROUS Norepinephrine transporter blockade → catecholamine excess. Additional sympathomimetics risk crisis. Beta-blockers contraindicated (unopposed alpha-1). Benzodiazepines; phentolamine for hypertension; nitrates. No beta-blockers.