Adrenergic agonists activate alpha or beta receptors directly or increase endogenous catecholamine activity indirectly. They range from emergency vasopressors to inhaled bronchodilators and centrally acting sympatholytics.

Alpha-1 activation causes smooth-muscle contraction; central alpha-2 activation reduces sympathetic outflow. Beta-1 increases cardiac rate and force, beta-2 relaxes bronchial and uterine smooth muscle, and beta-3 relaxes detrusor during bladder filling.

Examples include phenylephrine and midodrine; clonidine, methyldopa and dexmedetomidine; dobutamine; salbutamol and formoterol; mirabegron; and mixed catecholamines such as epinephrine and norepinephrine.

Uses include hypotension and shock, anaphylaxis, bronchospasm, chronic obstructive airway disease, overactive bladder, sedation, ADHD, orthostatic hypotension and selected obstetric or ophthalmic indications.

Adverse effects include hypertension, arrhythmia, tremor, anxiety, ischaemia and hypokalaemia. Central alpha-2 agonists cause sedation, dry mouth and bradycardia, while beta-3 agonists can increase blood pressure.

Avoid indiscriminate use in severe hypertension, unstable arrhythmia or ischaemic heart disease. Long-acting beta-2 agonists in asthma should be used according to controller-therapy guidelines rather than as unsupervised monotherapy.