Chapter 18: Adrenergic Drugs

The content covers endogenous catecholamines including epinephrine, norepinephrine, and dopamine, alongside synthetic medications such as dobutamine, phenylephrine, albuterol, and mirabegron. Understanding adrenergic receptor subtypes—alpha1, alpha2, beta1, beta2, and beta3—is essential to predicting clinical outcomes, as each subtype produces distinct physiological responses including vasoconstriction, bronchial smooth muscle relaxation, enhanced cardiac contractility, increased heart rate, and bladder detrusor muscle relaxation. Clinical applications are diverse and critical: epinephrine remains the cornerstone therapy for cardiac arrest and anaphylactic shock, beta2-agonists treat bronchospasm in asthma and chronic obstructive pulmonary disease, alpha1-agonists function as nasal decongestants and ophthalmic mydriatics, and beta3-agonists address overactive bladder conditions. The chapter differentiates between direct-acting agents that bind receptors, indirect-acting agents that enhance endogenous catecholamine release, and mixed-acting drugs combining both mechanisms. Additional emphasis falls on the brief half-life of naturally occurring catecholamines and the pharmacokinetic implications for drug administration. Critical nursing responsibilities include vigilant monitoring for adverse effects such as hypertension, cardiac dysrhythmias, tachycardia, tremor, and central nervous system overstimulation. Intravenous administration requires careful attention to prevent extravasation and tissue necrosis. Patient education must address proper inhaler technique, avoidance of over-the-counter sympathomimetic interactions, and recognition of toxicity symptoms. This chapter synthesizes adrenergic pharmacology essential for emergency medicine, critical care nursing, respiratory therapy, and cardiovascular crisis management.