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Systematic (IUPAC) name
Clinical data
  • C
    Commonly used to treat severe PIH
Routes of
Oral, intravenous
Pharmacokinetic data
Bioavailability 26-55%
Metabolism Hepatic
Biological half-life 2-4 hours
Excretion Renal
CAS Number 86-54-4
ATC code C02DB02 (WHO)
PubChem CID 3637
ChemSpider 3511
Chemical data
Formula C8H8N4
Molar mass 160.176 g/mol[[Script error: No such module "String".]]
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Hydralazine (Apresoline) is a direct-acting smooth muscle relaxant used to treat hypertension by acting as a vasodilator primarily in arteries and arterioles. By relaxing vascular smooth muscle, vasodilators act to decrease peripheral resistance, thereby lowering blood pressure and decreasing afterload.[1]

Mechanism of action

The mechanism of action of hydralazine is not well known. It interferes with the action of the second messenger IP3, limiting calcium release from the sarcoplasmic reticulum of smooth muscle. This results in an arterial and arteriolar relaxation.[2]

It recently has been identified as a nitric oxide donor.[3]

Activation of hypoxia-inducible factors has been suggested as a mechanism.[4]

Clinical Use

Hydralazine is not used as a primary drug for treating hypertension because it elicits a reflex sympathetic stimulation of the heart (the baroreceptor reflex). The sympathetic stimulation may increase heart rate and cardiac output, and may cause angina pectoris or myocardial infarction.[1] Hydralazine may also increase plasma renin concentration, resulting in fluid retention. In order to prevent these undesirable side-effects, hydralazine is usually prescribed in combination with a beta-blocker (e.g., propranolol) and a diuretic.[1]

Hydralazine is used to treat severe hypertension, but again, it is not a first-line therapy for essential hypertension. However, hydralazine is the first-line therapy for hypertension in pregnancy, with methyldopa.[5]

Side effects

Common side-effects include:

Patients given hydralazine over a period of six months may develop a lupus-like syndrome or other immune-related diseases that, in general, are reversible with withdrawal.[1] Hydralazine is differentially acetylated by fast and slow acetylator phenotypes, hence incidence of lupus-like disease in slow acetylators.[citation needed]

See also


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es:Hidralazina fa:هیدرالازین hr:Hidralazin it:Idralazina cloridrato ja:ヒドララジン pl:Hydralazyna

  1. 1.0 1.1 1.2 1.3 Harvey, Richard A., Pamela A. Harvey, and Mark J. Mycek. Lippincott's Illustrated Reviews: Pharmacology. 2nd ed. Philadelphia: Lipincott, Williams & Wilkins, 2000. 190.
  2. Rang, Dale, Ritter and Flower. Pharmacology. 6th Ed, 2007.
  3. "antihtn". Retrieved 2008-10-05. 
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  5. Bhushan, Vikas, Tao T. Lee, and Ali Ozturk. First Aid for the USMLE Step 1. New York: McGraw-Hill Medical, 2007. 251.
  6. Schoonen WM,et al. Do selected drugs increase the risk of lupus? A matched case-control study. Br J Clin Pharmacol. 2010 Oct;70(4):588-96. doi: 10.1111/j.1365-2125.2010.03733.x.
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