Are Lisinopril 40 mg and Benazepril 40 mg Interchangeable?
No, lisinopril 40 mg and benazepril 40 mg are not dose-for-dose interchangeable; benazepril 40 mg is approximately equivalent to lisinopril 20 mg based on a 2:1 conversion ratio. 1
Conversion Ratio
- The American College of Cardiology recommends a 2:1 conversion ratio between benazepril and lisinopril, meaning 40 mg of benazepril equals approximately 20 mg of lisinopril. 1
- This conversion accounts for differences in relative potencies at equivalent blood pressure-lowering effects, even though both drugs share the same maximum daily dose of 40 mg. 1
Dosing Equivalence Table
| Benazepril Dose | Lisinopril Equivalent |
|---|---|
| 10 mg | 5 mg |
| 20 mg | 10 mg |
| 40 mg | 20 mg |
Clinical Implications
- If converting from benazepril 40 mg to lisinopril: Start with lisinopril 20 mg once daily, not 40 mg, to avoid underdosing. 1
- If converting from lisinopril 40 mg to benazepril: The maximum allowable benazepril dose is 40 mg daily, which theoretically corresponds to lisinopril 20 mg based on the conversion ratio—this creates a practical ceiling that may result in less blood pressure control. 1
- When blood pressure remains uncontrolled on benazepril 40 mg (the maximum dose), add hydrochlorothiazide 12.5–25 mg rather than attempting to exceed the benazepril ceiling. 1
Monitoring After Conversion
- Check blood pressure within 1–2 weeks after conversion to ensure adequate control without excessive hypotension. 1
- Monitor serum creatinine and potassium levels within 1–2 weeks of conversion, as both ACE inhibitors can affect renal function and electrolyte balance. 1
- Watch for hypotension, especially in volume-depleted patients or those on diuretics, and monitor for hyperkalemia, particularly in patients with renal dysfunction or those taking potassium supplements. 1
Pharmacokinetic Differences
- Both medications are dosed once daily, making conversion straightforward from a dosing frequency perspective. 1
- Lisinopril has a bioavailability of approximately 25% and reaches peak concentrations at 6–8 hours, with effects lasting at least 24 hours. 2
- Benazepril is a prodrug rapidly converted to benazeprilat in the liver, with peak concentrations occurring earlier than lisinopril. 3
Common Pitfall to Avoid
Do not assume that because both drugs have a 40 mg maximum dose, they are interchangeable at that dose. The 2:1 conversion ratio means benazepril 40 mg provides roughly half the ACE inhibition of lisinopril 40 mg. 1 Failing to account for this difference will result in either underdosing (if switching from lisinopril 40 mg to benazepril 40 mg) or potential overdosing (if switching from benazepril 40 mg to lisinopril 40 mg without adjusting the dose).