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Sympathomimetic drugs

Last updated: March 7, 2021

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Sympathomimetics are substances that mimic or modify the actions of endogenous catecholamines of the sympathetic nervous system. Direct agonists directly activate adrenergic receptors while indirect agonists enhance the actions of endogenous catecholamines. Sympathomimetics stimulate alpha-1 adrenergic receptors, beta-adrenergic receptors, and dopamine (D) receptors in various target tissues, such as the eyes, heart, and vascular smooth muscle. The clinical indications for sympathomimetics are broad and include asthma, heart failure, shock, and anaphylaxis. Side effects include hypertension, sinus tachycardia, and skeletal muscle tremor.

Sympathomimetic drugs mimic or enhance the actions of endogenous catecholamines of the sympathetic nervous system (fight-or-flight reaction).

Direct sympathomimetic drugs

Direct sympathomimetics stimulate adrenergic and dopaminergic receptors directly.

Overview of direct sympathomimetics [1][2]
Drugs Action Cardiovascular effects Indications

Albuterol, salmeterol, formeterol, terbutaline

  • β2 > β1

Clonidine, guanfacine

  • α2
  • Lowers blood pressure (BP)
Dobutamine
Dopamine
  • Raises BP (at high doses), HR, CO
Epinephrine
  • Raises BP (at high doses), HR, CO
Fenoldopam
  • Raises CO, HR
  • Lowers BP (through vasodilatation)
Isoproterenol
  • β1 = β2
  • Marginal α effect
  • Raises CO, HR
  • Lowers BP (through vasodilatation)
Methyldopa
  • α2
  • Lowers BP
Midodrine
  • α1
Mirabegron
  • β3
  • Raises BP
Norepinephrine
  • α1 > α2 > β1
Oxymetazoline
  • α1 > α2
  • May raise BP
Phenylephrine
  • α1 > α2

DINED” is the acronym for examples of direct sympathomimetic drugs: Dopamine, Isoproterenol, Norepinephrine, Epinephrine, Dobutamine.

Indirect sympathomimetic drugs

Indirect sympathomimetics increase the synaptic activity of endogenous catecholamines by increasing presynaptic release or inhibiting reuptake.

Overview of indirect sympathomimetics [1][3]
Drugs Action Indications
Indirect general agonist Reuptake inhibitor Releases catecholamines
Amphetamines
  • Yes
  • Yes
  • Yes
Cocaine
  • Yes
  • Yes
  • No
Ephedrine
  • Yes
  • No
  • Yes
Overview of sympathomimetic effects [1][3]
Organ system Receptor Sympathomimetic effect
Eye
  • α1
  • α2
  • β2

Blood vessels

  • α1
  • α2
  • β2

Heart

  • β1
  • ↑ HR
  • ↑ Contractility
  • Automaticity and conduction velocity

Bronchi

  • β2
  • Bronchodilation

Gastrointestinal tract

  • α1
  • Sphincter contraction
  • β2
Liver
  • α1
  • β2
Pancreas
  • α2
  • β2
Kidneys
  • β1
Bladder
  • α1
  • β2
  • β3
Female reproductive organs
  • β2
Male reproductive organs
  • α1

Skeletal muscle

  • β2
  • β3

Adipose tissue

  • α2
  • β1–3

Both alpha-adrenergic and beta-adrenergic agonists are not fully selective at high doses.

Direct sympathomimetics

Side effects of direct sympathomimetics [1]
Drugs Side effects
α1-agonists [5]
α2-agonists
β1-agonists

β2-agonists

Catecholamines (e.g., epinephrine, norepinephrine, isoproterenol, dopamine, dobutamine) should only be administered if monitored by an experienced physician! High-dose catecholamine administration requires intra-arterial blood pressure monitoring.

Indirect sympathomimetics

Side effects of indirect sympathomimetics [1]
Drugs Side effects
Amphetamines
Cocaine
Ephedrine

In case of cocaine intoxication, the concurrent administration of beta-blockers can induce extreme hypertension and coronary vasospasm due to unopposed alpha-1 activation.

We list the most important adverse effects. The selection is not exhaustive.

  1. Katzung BG, Masters S, Trevor A. Basic and Clinical Pharmacology 12/E. McGraw Hill Professional ; 2012
  2. Giovannitti JA, Thoms SM, Crawford JJ. Alpha-2 adrenergic receptor agonists: a review of current clinical applications. Anesth Prog. 2015; 62 (1): p.31-39. doi: 10.2344/0003-3006-62.1.31 . | Open in Read by QxMD
  3. Becker DE. Basic and Clinical Pharmacology of Autonomic Drugs. Anesth Prog. 2012; 59 (4): p.159-169. doi: 10.2344/0003-3006-59.4.159 . | Open in Read by QxMD
  4. Krull KR. Pharmacology of Drugs Used to Treat Attention Deficit Hyperactivity Disorder in Children and Adolescents. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/pharmacology-of-drugs-used-to-treat-attention-deficit-hyperactivity-disorder-in-children-and-adolescents.Last updated: October 16, 2017. Accessed: December 10, 2017.
  5. Katzung B,Trevor A. Basic and Clinical Pharmacology. McGraw-Hill Education ; 2014
  6. Panus P, Katzung B, Jobst E, Tinsley S, Masters S, Trevor A. Pharmacology for the Physical Therapist. McGraw-Hill Education ; 2008