see also:

• vasodilators
• antihypertensives

• rapidly acting antihypertensive agent thought to directly act on peripheral arterioles primarily
• increases renal and cerebral blood flow, increases plasma renin activity and causes sodium and water retention
• reflex tachycardia usually occurswhich may limit its antihypertensive effect and thus an additional agent to block this (eg. beta adrenergic blockers) can provide further efficacy.
• plasma half life 3-7hrs
• duration of action post-dose 3-8hrs
• primarily metabolised by acetylation in the liver, with metabolites excreted in the kidneys
• slow acetylator phenotypes (50% of Caucasians and 20% of Asians) are at risk of toxicity with usual dosing

• hypotension
• concurrent monoamine oxidase inhibitors (MAOIs)
• aortic dissection
• hypersensitivity to hydralazine
• severe tachycardia
• cardiac failure
• systemic lupus erythematosus (SLE)

• slow acetylators
• concurrent antihypertensives may result in severe hypotension
• angina
• cerebral artery disease
• renal impairment
• liver impairment

• diarrhoea
• nausea
• vomiting
• tachycardia
• anorexia
• headache
• facial flushing
• blocked nose
• oedema
• angina
• rash
• peripheral neuritis
• systemic lupus erythematosus (SLE) like syndrome - especially at doses > 100mg/day

• rarely used in the ED
• onset 45min
• peak 1hr
• usual adult dose: 25mg bd increasing as needed to 50-200mg/day

• onset 10-20 minutes
• peak 15-30 minutes
• usual adult dose: 5-10mg iv slowly over 20 minutes, repeated if necessary