sympathomimetic

Sympathomimetics are drugs that mimic the effects of the sympathetic nervous system by stimulating adrenergic receptors or by increasing the availability of endogenous catecholamines such as norepinephrine and epinephrine. They are used to modulate cardiovascular, respiratory, nasal, and ocular functions, and some stimulant compounds affect central nervous system activity.

Pharmacologic action can be categorized as direct-acting, indirect-acting, or mixed-acting. Direct-acting agents bind and activate alpha- or beta-adrenergic receptors (for example, phenylephrine targeting alpha1 or albuterol targeting beta2). Indirect-acting agents increase synaptic catecholamines by promoting release or inhibiting reuptake (for example, amphetamine, pseudoephedrine). Mixed-acting agents have both actions (for example, ephedrine). The effects depend on receptor distribution and dose, with clinical outcomes ranging from vasoconstriction and increased heart rate to bronchodilation and mydriasis.

Common medical uses include management of hypotension and shock (epinephrine, norepinephrine, dobutamine), acute asthma or COPD exacerbations (albuterol), nasal congestion (pseudoephedrine, phenylephrine), and ophthalmic procedures requiring pupil dilation (phenylephrine). Epinephrine is also used in anaphylaxis and cardiac arrest, often in emergency settings, while local anesthetic solutions may include vasoconstrictors to reduce systemic absorption.

Adverse effects can include tachycardia, hypertension, arrhythmias, anxiety, tremor, and insomnia. Potential interactions include sensitization or exaggerated responses with monoamine oxidase inhibitors, tricyclic antidepressants, or certain cardiovascular drugs. Contraindications include severe hypertension, tachyarrhythmias, ischemic heart disease, and some states of glaucoma or peripheral vascular disease.