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]] <!-- interwiki --> [[hr:Hidralazin]] [[it:Idralazina cloridrato]] [[ja:ヒドララジン]]