IUPAC_name = 1-hydrazinophthalazine

CAS_number = 86-54-4
ATC_prefix = C02
ATC_suffix = DB02
PubChem = 3637
DrugBank =
C=8 | H=8 | N=4
molecular_weight = 160.176 g/mol
bioavailability =
protein_bound =
metabolism = Hepatic
elimination_half-life = 2-4 hours
excretion = Renal
pregnancy_category = C Commonly used to treat severe PIH
legal_status =
routes_of_administration = Oral, intravenous

Hydralazine hydrochloride (1-hydrazinophthalazine monohydrochloride; trade name 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.Harvey, Richard A., Pamela A. Harvey, and Mark J. Mycek. Lippincott's Illustrated Reviews: Pharmacology. 2nd ed. Philadelphia: Lipincott, Williams & Wilkins, 2000. 190.]


The mechanism of action of hydralazine is not well known. It interferes with the action the second messenger inositol triphosphate, limiting calcium release from the sarcoplasmic reticulum of smooth muscle. This results in an arterial and arteriolar relaxation.Rang, Dale, Ritter and Flower. Pharmacology. 6th Ed, 2007.]

An exam revision source declares that hydralazine works through a cGMP-mediated mechanism, resulting in smooth muscle relaxation.Bhushan, Vikas, Tao T. Lee, and Ali Ozturk. First Aid for the USMLE Step 1. New York: McGraw-Hill Medical, 2007. 251.]

It recently has been identified as a nitric oxide donor.cite web |url=http://faculty.swosu.edu/scott.long/phcl/antihtn.htm |title=antihtn |format= |work= |accessdate=2008-10-05]

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. Hydralazine may also increase plasma renin concentration, resulting in fluid retention. In order to prevent these undesirable side effects, hydralazine is generally prescribed in combination with a beta-blocker (e.g., propranolol) and a diuretic.

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.

ide effects

Common side effects include:
* Diarrhea
* Compensatory tachycardia due to baroreceptor reflex
* Headache
* Loss of appetite
* Nausea or vomiting
* Pounding heartbeat
* Drug-Induced Lupus Erythematosus

Patients given hydralazine over a peroid of six months may develop a lupus-like syndrome or other immune related diseases that generally are reversible with withdrawal. Hydralazine is differentially acetylated by fast and slow acetylator phenotypes thus incidence of lupus-like disease in slow acetylators.


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Look at other dictionaries:

  • hydralazine — noun Etymology: hydr + phthalic (acid) + azine Date: 1952 a vasodilator C8H8N4 used in the form of its hydrochloride to treat hypertension …   New Collegiate Dictionary

  • hydralazine — /huy dral euh zeen /, n. Pharm. a white crystalline powder, C8H8N4, that dilates blood vessels and is used in the treatment of hypertension. [1950 55; HYDR 2 + (PHTH)AL(IC) + AZINE] * * * …   Universalium

  • hydralazine — noun A direct acting smooth muscle relaxant used to treat hypertension by acting as a vasodilator primarily in arteries and arterioles …   Wiktionary

  • hydralazine — hy·dral·azine hī dral ə .zēn n an antihypertensive drug that is used in the form of its hydrochloride C8H8N4·HCl and produces peripheral arteriolar dilation by relaxing vascular smooth muscle * * * n. a vasodilator drug used, usually in… …   Medical dictionary

  • hydralazine — n. chemical substance used as a medication for treating high blood pressure …   English contemporary dictionary

  • hydralazine — hy·dral·a·zine …   English syllables

  • hydralazine — n. a vasodilator drug used, usually in conjunction with diuretics, to treat hypertension. It is given by mouth or by injection; side effects, including rapid heart rate, headache, faintness, and digestive upsets, can occur, especially at high… …   The new mediacal dictionary

  • hydralazine — noun an antihypertensive drug (trade name Apresoline) that dilates blood vessels; used (often with a diuretic) to treat hypertension and congestive heart failure • Syn: ↑Apresoline • Hypernyms: ↑antihypertensive, ↑antihypertensive drug,… …   Useful english dictionary

  • hydralazine hydrochloride — A vasodilating antihypertensive agent. * * * [USP] the monohydrochloride salt of hydralazine, used as an antihypertensive; administered orally, intramuscularly, or intravenously. It is also used in combination with nitrates, diuretics, or… …   Medical dictionary

  • Isosorbide dinitrate/hydralazine — is a fixed dose combination drug treatment specifically indicated for black people with congestive heart failure. It is a combination of hydralazine (an antihypertensive) and isosorbide dinitrate (a vasodilator). It is the first race based… …   Wikipedia

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