What is the recommended dose and administration of IV (intravenous) hydralazine for acute hypertension?

IV Hydralazine Dosing for Acute Hypertension

The recommended dose of IV hydralazine for acute hypertension is 10-20 mg administered as a slow IV bolus injection, which may be repeated as necessary with careful blood pressure monitoring. 1

Dosing and Administration Guidelines

• The FDA-approved dose for IV hydralazine is 20 to 40 mg, repeated as necessary, with lower doses recommended for patients with marked renal damage 1
• For preeclampsia specifically, a more conservative dosing regimen is recommended: 5 mg IV bolus initially, then 10 mg every 20 to 30 minutes to a maximum of 25 mg, repeated in several hours as necessary 2
• Blood pressure should be checked frequently as it may begin to fall within minutes after injection, with maximal decrease typically occurring between 10 to 80 minutes post-administration 1
• IV hydralazine should be administered directly into the vein as a bolus injection rather than added to infusion solutions 1
• The medication should be used immediately after opening the vial, and discolored solutions should be discarded 1

Clinical Considerations and Limitations

• IV 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 2
• Blood pressure begins to decrease within 10-30 minutes after administration, and the hypotensive effect typically lasts 2-4 hours 2
• Hydralazine can cause reflex tachycardia, which may be problematic in certain patient populations 3
• In patients with increased intracranial pressure, lowering blood pressure with hydralazine may increase cerebral ischemia 1
• Most patients can be transferred to oral hydralazine within 24 to 48 hours 1

Alternative Agents to Consider

• For hypertensive emergencies with specific comorbidities, other agents may be preferred:
  • Acute aortic dissection: esmolol or labetalol are preferred for rapid lowering of SBP to ≤120 mm Hg 2
  • Acute pulmonary edema: clevidipine, nitroglycerin, or nitroprusside are preferred 2
  • Acute coronary syndromes: esmolol, labetalol, nicardipine, or nitroglycerin are recommended 2

Monitoring and Safety Concerns

• A retrospective study found that IV hydralazine is commonly prescribed for non-urgent cases of hypertension in hospitalized patients, with changes in systolic BP being highly variable and sometimes associated with hypotension 4
• In one study, 11 out of 94 patients experienced hypotension as an adverse event following IV hydralazine administration 4
• Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration 1
• Careful monitoring is essential as the blood pressure response to hydralazine can be variable and unpredictable 2, 4

Clinical Pitfalls to Avoid

• Avoid using IV hydralazine in patients with increased intracranial pressure due to risk of cerebral ischemia 1
• Be cautious about overtreatment of asymptomatic hypertension in hospitalized patients, as one study found that 36% of PRN antihypertensive administrations were given for SBP <180 mmHg and DBP <110 mmHg (below the threshold for acute severe hypertension) 5
• Remember that many hospitalized patients receiving PRN antihypertensive medications are not continued on their home antihypertensive regimens during hospitalization (40.8% in one study), which may contribute to blood pressure management issues 5