Hydralazine is broken

Hydralazine is an erratic arterial vasodilator with unpredictable onset, duration, and blood-pressure response. In ED hypertension management, that matters: outside a true hypertensive emergency, IV blood-pressure lowering has unproven benefit and can create downstream harm, while cause-directed therapy beats reflexive treatment of the number.

Why Hydralazine Falls Apart

• Erratic hemodynamic profile: Hydralazine has a poorly understood mechanism and highly variable kinetics, with a latent onset around 5 to 15 minutes and delayed hypotension reported many hours later.
• Unpredictable pressure drop: A single 10 mg IV dose produced widely scattered blood-pressure responses, making hydralazine essentially a dice roll rather than a titratable ED antihypertensive.
• Reflex sympathetic surge: Direct arterial vasodilation triggers baroreceptor-mediated catecholamine release, so tachycardia and increased cardiac output can worsen the physiology you are trying to stabilize.
• Delayed iatrogenic spiral: Hypotension that appears hours later may be misread as sepsis or decompensation, prompting extra tests, antibiotics, or ICU escalation. We get into that downstream cascade in the episode.
• Frequent adverse effects: Headache, dizziness, and hypotension are common, and one cited series reported hypotension or dizziness in 16%, hardly the profile of a benign PRN medication.

Better Framing for ED Hypertension

• Cause before cuff: True hypertensive emergency management starts with the underlying diagnosis: SCAPE needs nitroglycerin, and aortic dissection needs impulse control with esmolol or labetalol.
• Bad fit emergencies: Hydralazine is a poor choice in myocardial infarction and aortic dissection because reflex tachycardia raises wall stress and myocardial oxygen demand; even the package insert warns against it.
• Asymptomatic pressure elevations: For uncomplicated asymptomatic hypertension, evidence does not show benefit from acute IV lowering in the ED, and aggressive treatment may cause more harm than good.
• Practical safer default: If you truly must lower blood pressure before admission, a one-time labetalol 5 to 10 mg is the headline alternative: generally safer, more predictable, and better tolerated.
• Fix the real issue: Check missed home medications and treat pain or nausea before blaming the blood pressure itself. That bedside reframing is worth hearing in the chapter.

Pregnancy and Inpatient Practice

• Pregnancy evidence signal: In severe hypertension of pregnancy, meta-analysis linked hydralazine to more maternal side effects, reflex tachycardia, delayed maternal hypotension, and more fetal bradycardia than alternatives.
• No outcome advantage: Despite its long hospital habit, hydralazine did not show better blood-pressure control than labetalol or nifedipine in pregnancy, undercutting the argument for routine use.
• Culture of reflex dosing: Hydralazine remains a common inpatient go-to, but one study found only 7.5% of physicians evaluated the patient before ordering it, a telling marker of number-chasing over diagnosis.
• Missed long-term management: In that same practice pattern, only 25% of patients had their chronic antihypertensive regimen adjusted, so acute PRN treatment often substitutes for actual blood-pressure care.

References:

1. Briggs, Blake MD. Clinical Controversies: Hydralazine is Broken (No Need to Fix It). Emergency Medicine News 44(2):p 14, February 2022. 
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9. Magee LA, Cham C, Waterman EJ, Ohlsson A, von Dadelszen P. Hydralazine for treatment of severe hypertension in pregnancy: meta-analysis. BMJ. 2003;327(7421):955-960. PMID: 14576246
10. Chobanian AV, Bakris GL, Black HR, et al. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 report [published correction appears in JAMA. 2003 Jul 9;290(2):197]. JAMA. 2003;289(19):2560-2572. PMID: 12748199