When is hydrazine contraindicated in a patient?

Contraindications for Hydralazine Administration

Hydralazine is contraindicated in patients with concurrent beta-blocker therapy, bradycardia, decompensated heart failure, reactive airways disease, chronic obstructive pulmonary disease, second or third-degree heart block, and in patients with advanced aortic stenosis. 1

Primary Contraindications

• Concurrent beta-blocker therapy - combined use can lead to severe hypotension and cardiovascular complications 1
• Bradycardia - hydralazine can cause reflex tachycardia which may worsen cardiac conditions in patients with pre-existing bradycardia 2
• Decompensated heart failure - hydralazine may further compromise cardiac function 1
• Reactive airways disease or chronic obstructive pulmonary disease (COPD) - can worsen respiratory function 1
• Second or third-degree heart block - hydralazine can further compromise cardiac conduction 1
• Advanced aortic stenosis - can dangerously reduce cardiac output 1

Additional Contraindications and Precautions

• Pregnancy - hydralazine should be used with caution, particularly in hypertensive emergencies of pregnancy where specific dosing protocols are recommended 3
• Hepatic impairment - hydralazine can cause hepatotoxicity, with case reports of fatal hepatorenal failure 4
  • Animal studies have demonstrated significant liver damage with hydrazine (a component of hydralazine), including marked hepatic necrosis, macrovesicular degeneration, and steatosis 5
  • Liver damage can begin within hours of exposure 6
• Renal impairment - hydralazine can affect renal function and has been associated with renal failure when used inappropriately 4
• Patients at risk of increased intraocular pressure (glaucoma) - can worsen this condition 1
• Patients at risk of increased intracranial pressure - can exacerbate this dangerous condition 1
• Patients with sulfite allergy - due to potential cross-reactivity 1

Clinical Considerations When Using Hydralazine

• Hydralazine has an unpredictable response and prolonged duration of action (2-4 hours), making it less desirable as a first-line agent for acute treatment in most patients 1, 3
• Blood pressure begins to decrease within 10-30 minutes after administration, and the effect lasts 2-4 hours 1
• The unpredictability of response makes hydralazine particularly problematic in acute settings 2
• Careful monitoring is essential as the blood pressure response can be variable 3
• For patients with normal or low blood pressure (e.g., 139/57 mmHg), hydralazine should be withheld to prevent hypotension 7

Alternative Agents to Consider

• For hypertensive emergencies with specific comorbidities, other agents may be preferred:
  • Acute aortic dissection: esmolol or labetalol 1
  • Acute pulmonary edema: clevidipine, nitroglycerin, or nitroprusside 1
  • Acute coronary syndromes: esmolol, labetalol, nicardipine, or nitroglycerin 1
  • For patients with bradycardia and hypertension: nicardipine or clevidipine may be more appropriate 2

Monitoring and Safety Concerns

• Monitor for reflex tachycardia, which is a common side effect 1
• Monitor hepatic function, as hydralazine has been associated with liver damage 5, 4
• Monitor renal function, particularly in patients with pre-existing renal impairment 4
• Intra-arterial blood pressure monitoring is recommended to prevent "overshoot" hypotension 1