Imidapril
**Imidapril** is an **angiotensin-converting enzyme (ACE) inhibitor** primarily used in veterinary medicine for the management of **congestive heart failure (CHF)** caused by mitral valve regurgitation or dilated cardiomyopathy in dogs. It is often used in conjunction with diuretics, pimobendan, or spironolactone for maximum efficacy. Additionally, it is utilized to manage **proteinuria** associated with chronic renal insufficiency, glomerular disorders, and protein-losing nephropathies, and may help reduce blood pressure in cases of **hypertension**. > **Clinical Warning:** ACE inhibitors are more likely to cause or exacerbate prerenal azotemia in hypotensive animals and those with poor renal perfusion (e.g., acute, oliguric renal failure). Use with extreme caution if hypotension, hyponatremia, or outflow tract obstruction are present. **Clinical Pearl:** While primarily licensed for dogs, the use of ACE inhibitors in cats with cardiac disease stems from extrapolation of theoretical benefits and studies in other species.
Mechanism: Imidapril acts by competitively inhibiting the **angiotensin-converting enzyme (ACE)**. * **Angiotensin I** → (ACE inhibition) → Decreased **Angiotensin II** production. * Inhibits the breakdown of **bradykinin** (a potent vasodilator). The overall cardiovascular effect is a reduction in preload and afterload via **venodilation and arteriodilation**, decreased salt and water retention via reduced **aldosterone** production, and inhibition of angiotensin-aldosterone-mediated cardiac and vascular remodeling. In the kidneys, it causes **efferent arteriolar dilation**, which reduces intraglomerular pressure and glomerular filtration, thereby decreasing **proteinuria**.
Dosing by species
- Congestive heart failure, proteinuria, or hypertension · 0.25 mg/kg · PO · q24h · For dogs weighing >4 kg.
- Cardiac disease or proteinuria · 0.5 mg/kg · PO · q24h · Anecdotal dose; no data available.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Acute renal failure
- Congenital heart disease
- Hemodynamically relevant stenoses (e.g., aortic stenosis)
- Obstructive hypertrophic cardiomyopathy
- Hypovolemia
- Breeding, pregnant, or lactating bitches
- Dogs weighing < 4 kg (safety not established)
Adverse effects
- Hypotension
- Hyperkalemia
- Azotemia
- Anorexia (rare)
- Vomiting (rare)
- Diarrhea (rare)
Drug interactions
- Spironolactone · Could result in hyperkalemia, though in practice, spironolactone and ACE inhibitors appear safe to use concurrently. · moderate
- Potassium supplements · Increased risk of hyperkalemia. · moderate
- NSAIDs · Increased risk of nephrotoxicity and decreased clinical efficacy of the ACE inhibitor. · major
- Diuretics · Increased risk of hypotension. · moderate
- Vasodilators (e.g., anesthetic agents, antihypertensives) · Increased risk of hypotension. · moderate
- Beta-blockers · Increased risk of hypotension when combined with negative inotropes. · moderate
Monitoring
- Blood pressure
- Serum creatinine and BUN
- Serum electrolytes (especially potassium and sodium)
- Clinical signs of hypotension (weakness, syncope)
Overdose
Doses of up to **5 mg/kg/day** have been well tolerated in healthy dogs. If overdosage occurs, monitor closely for signs of **hypotension** (weakness, lethargy, disorientation). If hypotension occurs, supportive care including intravenous fluids may be required.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.