Hydralazine
2504494
214428339
2008-05-23T14:43:38Z
PipepBot
4984067
robot Adding: [[it:Idralazina cloridrato]]
{{drugbox |
| IUPAC_name = 1-hydrazinophthalazine
| image = Hydralazine.svg
| 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 =
| legal_status =
| routes_of_administration = Oral, [[Intravenous therapy|intravenous]]
}}
'''Hydralazine hydrochloride''' (1-hydrazinophthalazine monohydrochloride; 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.<ref name=Harvey>Harvey, Richard A., Pamela A. Harvey, and Mark J. Mycek. Lippincott's Illustrated Reviews: Pharmacology. 2nd ed. Philadelphia: Lipincott, Williams & Wilkins, 2000. 190.</ref>
==Mechanism==
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.<ref name="Rand and Dale">Rang, Dale, Ritter and Flower. Pharmacology. 6th Ed, 2007.</ref>
An exam revision source declares that hydralazine works through a [[cGMP]]-mediated mechanism, resulting in smooth muscle relaxation.<ref name=Bhushan>Bhushan, Vikas, Tao T. Lee, and Ali Ozturk. First Aid for the USMLE Step 1. New York: McGraw-Hill Medical, 2007. 251.</ref>
==Clinical Use==
Hydralazine is not used as a primary drug for treating hypertension because it elicits a reflex [[Sympathetic nervous system|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]].<ref name=Harvey/> Hydralazine may also increase [[blood plasma|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]].<ref name=Harvey/>
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]].<ref name=Bhushan/>
==Side effects==
Common side effects include:
* [[Diarrhea]]
* Compensatory [[tachycardia]] due to baroreceptor reflex
* [[Headache]]
* [[anorexia (symptom)|Loss of appetite]]
* [[Nausea]] or [[vomiting]]
* [[palpitation|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.<ref name=Harvey/> Hydralazine is differentially acetylated by fast and slow acetylator phenotypes thus incidence of lupus-like disease in slow acetylators.
==References==
<references/>
{{Antihypertensives and diuretics}}
[[Category:Antihypertensive agents]]
[[Category:Hydrazines]]
[[Category:Pyridazines]]
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[[hr:Hidralazin]]
[[it:Idralazina cloridrato]]
[[ja:ヒドララジン]]