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Sympatholytic drugs

Last updated: March 9, 2021

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Sympatholytic agents inhibit the activity of the sympathetic nervous system, which is mediated by epinephrine and norepinephrine. They act primarily by blocking the postsynaptic adrenergic receptors (alpha and beta receptor antagonism) in target organs or by inhibiting the synthesis and storage of endogenous catecholamines (mainly norepinephrine). A sympatholytic effect can also be achieved via stimulation of the presynaptic alpha-2 receptor with an alpha-2 agonist, which inhibits the release of catecholamines. Sympatholytic drugs are most commonly used in the treatment of ischemic heart disease and hypertension but may also be used for urinary retention secondary to benign prostatic hyperplasia and for psychiatric conditions such as anxiety disorders and posttraumatic stress disorder.

Beta receptor antagonists are discussed in detail in a separate article.

All sympatholytic drugs inhibit the activity of the sympathetic nervous system via one of the following mechanisms:

Sympatholytic drugs
Classification Mechanism of action Main effects Indications
Alpha receptor antagonists Alpha-1 receptor antagonists
Nonselective alpha receptor antagonists
Alpha-2 receptor agonists [1]
Beta receptor antagonists Beta-1 antagonists
Beta-2 antagonists
  • None
Nonselective beta receptor antagonists
Antagonists of alpha receptors and beta receptors
Monoamine-depleting agents/
inhibitors of noradrenaline storage

All drug groups that directly inhibit the sympathetic nervous system (i.e., alpha receptor antagonists, beta receptor antagonists, and drugs that reduce sympathetic tone) are treatment options for arterial hypertension.

Overview of alpha receptor antagonists
Class Drugs Indication Adverse effects [2]
Alpha-1 receptor antagonists Doxazosin
Terazosin
Tamsulosin (blocks alpha-1A/D > alpha-1B receptors)
Alfuzosin
Silodosin
Prazosin
Alpha-2 receptor antagonists Mirtazapine
  • Depression
Nonselective alpha receptor antagonists

Phenoxybenzamine

Phentolamine

Alpha receptor antagonists are usually only second-line drugs for the treatment of hypertension since they do not improve prognosis. They are predominantly used in combination regimens.

Overview of alpha-2 receptor agonists [1]
Drugs Indication Adverse effects

Clonidine [3]

Guanfacine [4]

Methyldopa [5]
Tizanidine [6]
Dexmedetomidine [7]
  • Sedation
Overview of monoamine-depleting agents
Drugs Mechanism of action Indication Adverse effects
Tetrabenazine
Reserpine
  1. 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
  2. Clonidine. https://www.drugs.com/pro/clonidin. Updated: November 1, 2017. Accessed: March 10, 2018.
  3. Guanfacine. https://www.drugs.com/pro/guanfacine.html. Updated: November 1, 2017. Accessed: March 10, 2018.
  4. Methyldopa Side Effects. https://www.drugs.com/sfx/methyldopa-side-effects.html. . Accessed: March 10, 2018.
  5. Tizanidine. https://www.drugs.com/pro/tizanidine.html. Updated: October 1, 2017. Accessed: March 10, 2018.
  6. Dexmedetomidine. https://www.drugs.com/pro/dexmedetomidine-hydrochloride-injection.html. Updated: July 1, 2017. Accessed: March 10, 2018.
  7. Kaplan SA. Side effects of alpha-blocker use: retrograde ejaculation. Rev Urol. 2009; 11 (Suppl 1): p.S14-8.
  8. Dean M, Sung V. Review of deutetrabenazine: a novel treatment for chorea associated with Huntington's disease. Drug Design, Development and Therapy. 2018; Volume 12 : p.313-319. doi: 10.2147/dddt.s138828 . | Open in Read by QxMD
  9. Cheung M, Parmar M. Reserpine. StatPearls. 2021 .
  10. Katzung B,Trevor A. Basic and Clinical Pharmacology. McGraw-Hill Education ; 2014