You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Angiotensin-converting enzyme (ACE) inhibitors 

ACE inhibitors block the conversion of angiotensin I to angiotensin II which 

• is a potent vasoconstrictor
• causes myocardial remodelling
• stimulates aldosterone production which contributes to oedema through water retention

So, ACE inhibitors :

• Cause vasodilation - due to reduced vasoconstriction and also increased bradykinin concentrations
• Lower blood pressure 
• Reduce volume overload on the heart
• Decrease aldosterone secretion - resulting in decreased sodium and water retention

In human medicine ACE inhibitors are routinely used in patients with congestive heart failure following myocardial infarction and they are widely used in veterinary medicine.

Side effects and contra-indications reported in humans include :

• Dry cough
• Altered taste
• Skin rash
• Fever
• Hypotension - leading to syncope -especially after the first dose
• Hyperkalaemia
• Angioedema (potentially fatal)
• Renal failure (reversible) 
• They are contraindicated in pregnancy
• The concurrent use of potassium-sparing diuretics (spironolactone) is not advised

In veterinary data sheets :

• Tiredness or dizziness are reported to be rare side-effects
• Transient, mild azotaemia may occur
• Hypotension may occur
• Incoordination may occur 
• They are contraindicated in aortic stenosis where there is reduced cardiac output
• The concurrent use of potassium-sparing diuretics (spironolactone) is not advised

In one study* use of the ACE inhibitor benazepril in dogs with congestive heart failure produced the following findings :

• 70% of dogs had improved according to the New York Heart Association classification for grades of heart failure
• Exercise tolerance improved
• The cardiogenic cough improved
• Heart rate decreased significantly

Side-effects reported

• 5/40 dogs developed syncope at the beginning of the study
• 2/40 dogs were inappetant during the first few weeks of the study

The authors concluded that benazepril was an effective and well-tolerated therapeutic agent for the treatment of congestive heart failure in dogs.

(* Wien Tierarztl Mschr (1999) 86 :289-300.)

Updated January 2016