What is the recommended dosing and administration of hydralazine (hydralazine) infusion for managing severe hypertension?

Hydralazine Infusion Dosing and Administration for Severe Hypertension

For severe hypertension management, intravenous hydralazine should be administered as a 20-40 mg dose, repeated as necessary, with careful blood pressure monitoring as effects may begin within minutes and reach maximum effect in 10-80 minutes. 1

Dosing Recommendations

• The FDA-approved dosing for IV hydralazine is 20-40 mg, repeated as necessary, with lower doses recommended for patients with marked renal damage 1
• For obstetrical patients with severe hypertension, a more conservative dosing regimen is recommended: 5-10 mg IV bolus initially, with subsequent doses of 5-10 mg IV every 20-30 minutes as needed 2
• IV hydralazine should be administered as a direct bolus injection rather than added to infusion solutions 1
• Blood pressure typically begins to decrease within 10-30 minutes after administration, with maximum effect occurring in 10-80 minutes 3, 1
• The duration of action is typically 1-4 hours for IV administration 2

Administration Considerations

• Hydralazine should be used only when oral administration is not possible 1
• The medication should be used immediately after opening the vial 1
• Solutions that have discolored upon contact with metal should be discarded 1
• Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration 1
• Most patients can be transferred to oral hydralazine within 24-48 hours 1

Monitoring and Safety

• Blood pressure should be checked frequently after administration, as the response can be variable and unpredictable 4, 1
• Hydralazine has an unpredictable response and prolonged duration of action, making it less desirable as a first-line agent for acute treatment in most patients 5, 4
• In cases of increased intracranial pressure, lowering blood pressure with hydralazine may increase cerebral ischemia 1
• Common adverse effects include reflex tachycardia, headache, flushing, and vomiting 2
• Hypotension is a significant concern, occurring in approximately 11% of patients in one study 6

Clinical Context and Indications

• Hydralazine is specifically indicated for hypertensive emergencies in eclampsia 2
• For most other hypertensive emergencies, agents with more predictable responses such as sodium nitroprusside, nicardipine, or labetalol are preferred 2, 5
• The Society for Maternal-Fetal Medicine considers hydralazine (5 or 10 mg IV) a standard antihypertensive agent for severe hypertension in obstetrical patients 2
• Treatment should be initiated within 60 minutes of the onset of severe hypertension in obstetrical patients 2

Alternative Agents to Consider

• For non-obstetrical hypertensive emergencies, other agents may be more appropriate:
  • Sodium nitroprusside (0.25–10 μg/kg/min as IV infusion) for most hypertensive emergencies 2
  • Nicardipine (5–15 mg/h IV) for most hypertensive emergencies except acute heart failure 2
  • Labetalol (20–80 mg IV bolus every 10 min) for most hypertensive emergencies except acute heart failure 2, 5

Practical Application

• For severe hypertension requiring immediate intervention, administer hydralazine as a direct IV bolus 1
• Start with 20 mg for non-obstetrical patients or 5-10 mg for obstetrical patients 2, 1
• Monitor blood pressure every 5-15 minutes during initial treatment 5
• If blood pressure remains elevated after 20-30 minutes, administer an additional dose 2
• If hydralazine fails to adequately control blood pressure, consider switching to an alternative agent such as labetalol or nicardipine 5