What are some IV (intravenous) ACE (angiotensin-converting enzyme) inhibitors for acute elevated blood pressure?

IV ACE Inhibitor for Acute Elevated Blood Pressure

Enalaprilat is the only IV ACE inhibitor available for acute elevated blood pressure, administered at 0.625–1.25 mg IV, with onset of action in 5–15 minutes and duration of 4–6 hours. 1, 2

Available IV ACE Inhibitor

Enalaprilat is the sole intravenous ACE inhibitor option:

• Dosing: 0.625–1.25 mg IV bolus 1
• Onset: 5–15 minutes 1
• Duration: 4–6 hours 1
• Mechanism: Active metabolite of oral enalapril; inhibits angiotensin-converting enzyme, reducing angiotensin II and aldosterone secretion 2

Clinical Context and Limitations

When Enalaprilat May Be Considered

Enalaprilat has limited and specific indications in hypertensive emergencies:

• Malignant hypertension with high renin activity: ACE inhibitors are mentioned as an option by some teams, but must be started at very low doses to prevent sudden BP drops 1
• Acute renal failure: Listed as an alternative agent in some guidelines 1
• Volume-depleted patients: Requires extreme caution; IV saline should be available to correct precipitous BP falls 1

Critical Warnings

Enalaprilat is NOT first-line therapy for most hypertensive emergencies due to several important limitations:

• Unpredictable BP response: Particularly in malignant hypertension where renin-angiotensin system activation is highly variable 1
• Risk of precipitous hypotension: Especially dangerous in volume-depleted patients (common due to pressure natriuresis) 1
• Relatively slow onset: 15-minute onset is slower than preferred agents like nitroprusside (immediate) or labetalol (5–10 minutes) 1
• Dose not easily adjusted: Unlike continuous infusions, bolus dosing limits titratability 1

Preferred First-Line Alternatives

For most hypertensive emergencies, labetalol or nicardipine are preferred over enalaprilat:

• Labetalol: 0.25–0.5 mg/kg IV bolus or 2–4 mg/min continuous infusion; first-line for most emergencies 1
• Nicardipine: 5–15 mg/h continuous infusion; equally effective and widely available 1
• Nitroprusside: 0.3–10 μg/kg/min for acute pulmonary edema or aortic dissection (with beta-blocker) 1

Absolute Contraindications to Enalaprilat

• Pregnancy/eclampsia: ACE inhibitors are absolutely contraindicated 1
• History of angioedema with ACE inhibitors 1
• Bilateral renal artery stenosis or stenosis of solitary kidney 1
• Acute myocardial infarction: IV ACE inhibitors are contraindicated in the first 24 hours due to hypotension risk 1

Practical Considerations

If enalaprilat is used despite limitations:

• Start with 0.625 mg (lower dose) rather than 1.25 mg to assess response 1, 3
• Have IV saline readily available for precipitous BP drops 1
• Monitor for hyperkalemia, particularly with renal insufficiency 2
• Adjust dosing in renal impairment (GFR ≤30 mL/min requires dose reduction) 2
• Recognize that response is more predictable in high-renin states 4, 3

Bottom line: While enalaprilat exists as an IV ACE inhibitor option, it should rarely be chosen over labetalol, nicardipine, or other preferred agents for acute hypertensive emergencies given its unpredictable response, risk of precipitous hypotension, and slower onset. 1