Benazepril
Benazepril is an **Angiotensin-Converting Enzyme (ACE) inhibitor** widely used in veterinary medicine for the management of heart failure, systemic hypertension, chronic renal failure, and protein-losing glomerulonephropathies in dogs and cats. **Clinical Pearls:** * Unlike enalapril, which is almost exclusively cleared by the kidneys, benazepril's active metabolite (benazeprilat) is cleared via **both hepatic (55%) and renal (45%) routes** in dogs. This dual-excretion pathway makes it a preferred ACE inhibitor in patients with concurrent renal impairment. * It is particularly beneficial in reducing intraglomerular hypertension, thereby decreasing proteinuria in chronic kidney disease. * Because it lacks a sulfhydryl group (unlike captopril), it has a lower tendency to cause immune-mediated adverse reactions.
Mechanism: Benazepril is a **prodrug** that is hydrolyzed in the liver to its active metabolite, **benazeprilat**. It competitively inhibits **Angiotensin-Converting Enzyme (ACE)**. * **Pathway:** Angiotensin I โ (blocked by ACE) โ **Angiotensin II** * **Hemodynamic Effects:** By preventing the formation of Angiotensin II (a potent vasoconstrictor), benazepril promotes vasodilation, reducing both preload and afterload in heart failure patients. * **Renal Effects:** It dilates the efferent arterioles of the glomerulus more than the afferent arterioles, reducing intraglomerular capillary pressure and subsequently decreasing proteinuria. * **Endocrine Effects:** Decreased Angiotensin II leads to reduced secretion of **aldosterone** from the adrenal cortex, minimizing sodium and water retention.
Dosing by species
- Adjunctive treatment of heart failure ยท 0.25-0.5 mg/kg PO once daily ยท PO ยท q24h
- Adjunctive treatment of heart failure ยท 0.25-0.5 mg/kg PO once to twice daily ยท PO ยท q12-24h
- Adjunctive treatment of hypertension and/or proteinuria (first step) ยท 0.5 mg/kg q12h ยท PO ยท q12h ยท As a first step drug for systolic hypertension >160 mmHg, diastolic >120 mmHg
- Adjunctive treatment of hypertension and/or proteinuria ยท 0.25-0.5 mg/kg q12-24h ยท PO ยท q12-24h ยท Co-administration with a calcium channel antagonist may lower blood pressure when monotherapy is not sufficient.
- Hypertension associated with protein-losing renal disease ยท 0.5 mg/kg PO once daily (q24h) ยท PO ยท q24h
- Proteinuria, hypertension ยท 0.25-1 mg/kg PO q12-24h ยท PO ยท q12-24h ยท Potentially could worsen preexisting azotemia; lower dose and monitoring recommended.
- Heart failure ยท 0.25-0.5 mg/kg ยท PO ยท q24h ยท Long-term ยท Adjunctive treatment. Often used in conjunction with diuretics, pimobendan, spironolactone, or digoxin.
- Adjunctive treatment of hypertension/proteinuria ยท 0.25-0.5 mg/kg ยท PO ยท q12-24h ยท Long-term ยท May reduce blood pressure; more potent in dogs than cats.
- Adjunctive treatment of heart failure ยท 0.25-0.5 mg/kg PO once daily ยท PO ยท q24h
Routes of administration
Contraindications
- Known hypersensitivity to ACE inhibitors
Adverse effects
- Anorexia
- Vomiting
- Diarrhea
- Hypotension
- Renal dysfunction (worsening azotemia)
- Hyperkalemia
Drug interactions
- Aspirin ยท May potentially negate the decrease in systemic vascular resistance induced by ACE inhibitors (though low-dose aspirin may not significantly affect hemodynamics).
- Antidiabetic Agents (insulin, oral agents) ยท Possible increased risk for hypoglycemia; enhanced monitoring recommended.
- Diuretics (e.g., furosemide, hydrochlorothiazide) ยท Potential for increased hypotensive effects. Reducing furosemide doses by 25-50% is often recommended when initiating ACE inhibitors for heart failure.
- Potassium-Sparing Diuretics (e.g., spironolactone, triamterene) ยท Increased risk of hyperkalemia; enhanced monitoring of serum potassium is required.
- Lithium ยท Possible increased serum lithium levels; increased monitoring required.
- Potassium Supplements ยท Increased risk for hyperkalemia. ยท major
- Spironolactone ยท Potential for hyperkalemia due to additive potassium-sparing effects, though concurrent use is generally safe in practice. ยท moderate
- NSAIDs ยท Increased risk of nephrotoxicity and decreased clinical efficacy of benazepril. ยท major
- Diuretics (e.g., Furosemide) ยท Increased risk of hypotension and prerenal azotemia. ยท moderate
- Vasodilators (e.g., Amlodipine, Anesthetic agents) ยท Additive hypotensive effects. ยท moderate
- Beta-blockers ยท Increased risk of hypotension due to negative inotropic effects. ยท moderate
Monitoring
- Clinical signs of Congestive Heart Failure (CHF)
- Serum electrolytes (especially potassium)
- Renal panel (Creatinine, BUN)
- Urine protein (UPC ratio)
- Blood pressure (especially if treating hypertension or if signs of hypotension arise)
Overdose
In overdose situations, the primary concern is **hypotension**. * **Treatment:** Supportive treatment with volume expansion using normal saline is recommended to correct blood pressure. * **Monitoring:** Because of the drug's long duration of action, prolonged monitoring and treatment may be required. * **Decontamination:** Recent massive overdoses should be managed using standard gut-emptying protocols (emesis, activated charcoal) as appropriate.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.