PH2.{1,3} | PH2.{1,3} | Adrenergic Drugs and Emergency Sympathomimetic Use — SDL Guide — Summary & Reflection

KEY TAKEAWAYS

Adrenergic drugs act on four main receptor families: α1 (vasoconstriction), α2 (presynaptic inhibition), β1 (cardiac inotropy/chronotropy), and β2 (bronchodilation, vasodilation). Agonists include adrenaline (non-selective), noradrenaline (α1/α2/β1), dopamine (dose-dependent D1→β1→α1), dobutamine (selective β1), phenylephrine (selective α1), and salbutamol (selective β2). Antagonists span alpha-blockers (phenoxybenzamine irreversible; phentolamine reversible; prazosin selective α1) and beta-blockers (propranolol non-selective; atenolol/metoprolol/bisoprolol cardioselective β1; carvedilol/labetalol mixed α+β).

In emergencies: anaphylaxis requires adrenaline 0.5 mg IM (lateral thigh); septic shock requires noradrenaline infusion to MAP ≥65 mmHg; cardiac arrest requires adrenaline 1 mg IV every 3–5 min; acute HF uses dobutamine infusion; bradycardia and OPC poisoning use atropine (muscarinic antagonist). The alpha-first rule in phaeochromocytoma is a safety-critical principle. All catecholamines have half-lives of 1–3 minutes, mandating IV infusion for sustained effect. Never give beta-blockers before alpha-blockade in phaeochromocytoma — this causes unopposed α1 vasoconstriction and hypertensive crisis.

REFLECT

Think about the last resuscitation scenario you observed or participated in (or consider the hook case at the start of this guide). How did the pharmacological principles covered here — receptor selectivity, dose-dependence, route of administration — play out in the clinical decisions made? If you had been the prescriber, would you have reached for the right drug, dose, and route without hesitation? What would you need to rehearse to feel confident in that 90-second window of an anaphylaxis call? Identify one pharmacological concept from this SDL that surprised you and note how it changes your thinking about emergency drug selection.