Can I use enalaprilat (Angiotensin-Converting Enzyme inhibitor) as an alternative to manage hypertension in a patient with severe hypertension, bradycardia, and an allergy to hydralazine, who is currently on amlodipine?

Enalaprilat as an Alternative for Severe Hypertension with Bradycardia

Yes, enalaprilat is an appropriate alternative for managing severe hypertension in this patient with bradycardia and hydralazine allergy, as it effectively lowers blood pressure without causing reflex tachycardia or worsening bradycardia. 1

Why Enalaprilat is Suitable for This Clinical Scenario

Enalaprilat does not cause bradycardia or negative inotropic effects, making it safe for patients with a baseline heart rate of 55 bpm. 2 The drug works by inhibiting angiotensin-converting enzyme, leading to decreased vasopressor activity and aldosterone secretion without affecting heart rate. 1

Pharmacodynamic Profile Supporting Use in Bradycardia

• Enalaprilat provides predictable blood pressure reduction with onset within 15 minutes and maximum effect at 1-4 hours. 1
• Unlike hydralazine, enalaprilat does not cause reflex tachycardia, which paradoxically makes it safer in bradycardic patients who cannot tolerate further autonomic stress. 2, 1
• The duration of action is approximately 6 hours for recommended doses, allowing for controlled titration. 1

Contraindicated Alternatives in This Patient

Several other antihypertensive options must be avoided given the clinical context:

• Hydralazine is absolutely contraindicated due to documented allergy. 2
• Non-dihydropyridine calcium channel blockers (diltiazem, verapamil) would worsen bradycardia through negative chronotropic effects. 3, 2
• Beta-blockers would further reduce heart rate below the already concerning rate of 55 bpm. 2
• Moxonidine is associated with increased mortality in heart failure patients. 3, 2

Practical Dosing Algorithm for Enalaprilat

Initial Assessment

• Verify the patient's current blood pressure is ≥140/90 mmHg and requires intervention. 4
• Ensure diastolic blood pressure is >60 mmHg before administering any antihypertensive to prevent coronary hypoperfusion. 2, 4
• Check baseline renal function and serum potassium. 1

Dosing Strategy

• Initial dose: 0.625-1.25 mg IV over 5 minutes for patients already on amlodipine. 1
• Repeat dosing every 6 hours as needed based on blood pressure response. 1
• Target blood pressure <140/90 mmHg, but avoid diastolic BP <60 mmHg. 2, 4

Critical Monitoring Parameters

• Monitor blood pressure every 15-30 minutes initially after IV administration. 2
• Continuously monitor heart rate, maintaining target >50 bpm. 2
• Check for symptomatic hypotension, especially in the first 1-4 hours when maximum effect occurs. 1

Important Safety Considerations

Risk of Excessive Hypotension

Enalaprilat carries risk of excessive hypotension, particularly in volume-depleted patients or those on high-dose diuretics. 1 Given that this patient is already on amlodipine, start with the lower end of the dosing range (0.625 mg) to avoid additive hypotensive effects. 1

Renal Function Monitoring

• Enalaprilat is primarily renally excreted (>90% unchanged in urine within 24 hours). 1
• If glomerular filtration rate is ≤30 mL/min, the effective half-life is prolonged and dose adjustment is required. 1
• Monitor serum creatinine and potassium within 1 week of initiation. 3

Angioedema Risk

Angioedema can occur at any time during ACE inhibitor therapy and may involve the face, extremities, lips, tongue, glottis, or larynx. 1 If laryngeal edema occurs, immediately discontinue enalaprilat and administer subcutaneous epinephrine 1:1000 (0.3-0.5 mL). 1

Transition to Oral Therapy

Once blood pressure is controlled and the patient can take oral medications:

• Continue amlodipine as the calcium channel blocker component. 2
• Consider adding an oral ACE inhibitor (enalapril) or ARB for long-term management. 3
• The combination of ACE inhibitor and calcium channel blocker is guideline-recommended for hypertension management. 3

Common Pitfalls to Avoid

• Do not administer enalaprilat if diastolic BP is already <60 mmHg, as this increases risk of coronary hypoperfusion. 2, 4
• Avoid combining enalaprilat with potassium-sparing diuretics or aldosterone antagonists without close potassium monitoring, as hyperkalemia risk increases. 3, 1
• Do not use in patients with bilateral renal artery stenosis, as this can precipitate acute renal failure. 1
• Monitor for hypotension more closely in patients on concurrent diuretics, as the combination increases risk of excessive blood pressure reduction. 1