From the FDA Drug Label
The dose for patients being converted to enalaprilat injection, USP from oral therapy for hypertension with enalapril maleate is 1.25 mg every six hours.
- Conversion from oral to IV is possible, but the label does not specifically address the scenario of a patient already on lisinopril.
- The label does provide guidance on converting from enalapril maleate (an oral form of enalapril) to enalaprilat (the IV form).
- However, lisinopril is a different medication, although it is also an ACE inhibitor like enalapril.
- Given the lack of direct information on converting from lisinopril to enalaprilat IV, a conservative approach would be to exercise caution and consider the potential risks of switching between these two medications 1.
From the Research
No, enalapril IV should not be given to a patient already taking lisinopril, as both medications are angiotensin-converting enzyme (ACE) inhibitors and administering them together would constitute duplicate therapy, potentially leading to enhanced side effects including severe hypotension, hyperkalemia, and acute kidney injury 2.
Reasoning
The primary concern with administering enalapril IV to a patient already taking lisinopril is the risk of additive effects, which could lead to severe hypotension, hyperkalemia, and acute kidney injury. This is because both enalapril and lisinopril work by blocking the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor. By inhibiting this conversion, both drugs decrease blood pressure and increase renal blood flow, but when used together, these effects can be excessive.
Alternative Approach
If IV ACE inhibitor therapy is needed for a patient on lisinopril, the oral lisinopril should be discontinued first. The healthcare provider should then determine an appropriate dosing of IV enalapril based on the patient's condition, blood pressure, and kidney function. Alternatively, if urgent blood pressure control is needed in a patient on lisinopril, other IV antihypertensive classes such as calcium channel blockers, beta-blockers, or vasodilators would be more appropriate choices, as they do not share the same mechanism of action as ACE inhibitors and thus do not pose the same risk of additive effects.
Key Considerations
- Duplicate Therapy: Administering enalapril IV to a patient already on lisinopril constitutes duplicate therapy, which is unnecessary and potentially harmful.
- Additive Effects: The combined use of enalapril and lisinopril can lead to excessive blood pressure lowering, hyperkalemia, and renal impairment due to their shared mechanism of action.
- Alternative Therapies: Other classes of antihypertensive drugs can be used in emergencies without the risk of duplicate therapy or additive harmful effects.