Hydralazine

Hydralazine

File:Hydralazine.svg
Systematic (IUPAC) name
1-hydrazinylphthalazine
Clinical data
Pregnancy category	C Commonly used to treat severe PIH
Routes of administration	Oral, intravenous
Pharmacokinetic data
Bioavailability	26-55%
Metabolism	Hepatic
Biological half-life	2-4 hours
Excretion	Renal
Identifiers
CAS Number	86-54-4
ATC code	C02DB02 (WHO)
PubChem	CID 3637
ChemSpider	3511
Chemical data
Formula	C8H8N4
Molar mass	160.176 g/mol[[]]
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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.

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.

It recently has been identified as a nitric oxide donor.

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

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 usually 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.

Side effects

Common side-effects include:

• Diarrhea
• Compensatory tachycardia due to baroreceptor reflex ->Angina
• Headache
• Loss of appetite
• Nausea or vomiting
• Depression
• Pounding heartbeat
• Drug-Induced Lupus Erythematosus

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. Hydralazine is differentially acetylated by fast and slow acetylator phenotypes, hence incidence of lupus-like disease in slow acetylators.

See also

• Cadralazine
• Dihydralazine
• Endralazine

References

de:Hydralazin zh:肼屈嗪