The active ingredient in Fortekor is Benazepril hydrochloride. It is classified as the first of a second generation of Angiotensin Converting Enzyme (ACE) inhibitors. Benazepril hydrochloride was discovered by CIBA-GEIGY (now Novartis Animal Health) Pharmaceuticals in the USA. It has been used in man for the last 15 years for the treatment of hypertension (high blood pressure) and for congestive heart failure. Benazepril is what is called a pro-drug. This means that it is not in itself the active drug in the body. The body changes an oral Benazepril tablet in the liver, to the active substance Benazeprilat.
Much of the early development work with humans involved dogs. When it was realized that there was a veterinary potential for ACE inhibitors, Novartis Animal Health used their data and information to compile a registration dossier for the product we now know as Fortekor.
Estimates vary, but heart disease affects approximately 7% of all dogs in Canada. Severity ranges from a murmur to full blown heart failure (classified in "grades" where Grade 1 is mild and Grade 4 is severe). There are two classification systems for heart failure:
- ISACHC: Class 1, 2, 3; or
- NYHA: Grade I, II, III, IV.
The two main types of heart failure that affect dogs are cardiomyopathy (where the heart muscle undergoes general failure) and endocardiosis (where the valves or internal structure of the heart is faulty). Cardiomyopathy generally affects larger breeds of dog (about 30% of heart cases) and endocardiosis is seen in smaller breeds to make up about 70% of cardiac patients. Common symptoms for heart failure are coughing, exercise intolerance, weight loss, and possibly a buildup of fluid in the abdomen called ascites. Symptoms, drugs, treatments and drug interactions are far too varied and complicated to summarize here. If you are at all concerned about the health of your dog for any reason, your veterinarian should be consulted as they will be able to provide more detail about heart failure and which specific type is affecting your dog.
When dogs suffer from heart failure, vital organs such as the kidneys, begin a cycle called the Renin-Angiotensin-Aldosterone (or RAA) system.
This system is designed to react to a drop in blood supply by producing a vasoconstrictor to affect the peripheral blood vessels of the body, which in turn increases blood pressure and blood flow, and allows more blood to be supplied to these vital organs. A triggering of the RAA system also causes the body to increase its absorption of salt and water, to increase blood volume and supply more blood to the kidney. In the short term, this is a good thing for the kidneys as it replenishes the drop in blood supply. But in the long term this added pressure increases the workload for the heart. If the heart is failing (which caused the RAA system to be activated in the first place) an added workload will ultimately hasten the disease process, further compromising the diseased heart.
The end result of heart disease is more work for the failing heart to do.
Mode of Action
Benazepril acts to inhibit the RAA system, reducing blood pressure back to normal levels, and reducing the amount of work the failing heart has to do. Fortekor prevents the body from harmful vasoconstriction and complicating heart disease. By interfering with the RAA system Fortekor also prevents the absorption of salt and water by preventing the release of a hormone called ALDOSTERONE. All these actions ultimately relieve the symptoms of heart disease and lengthen the life span of the dog. Dogs suffering from heart failure must be monitored by the veterinarian periodically to monitor the progress of the disease in case treatments need to be altered. Your veterinarian will examine your dog and will make the necessary changes based on test results and clinical signs. Dosing instructions are always supplied and monitored by the prescribing veterinarian.
In pre-clinical trials there were no serious reactions when the drug was given at 200x the label dosage. Some ACE inhibitors are excreted almost completely by the kidney, which can adversely affect an already compromised pet (which is common in dogs with heart failure). Fortekor helps your dog's heart and is kind to the kidneys. There are no contraindications with any other medications your dog might currently be on. In a large percentage of cases the effectiveness of Fortekor is enough to allow other medications to be reduced by your veterinarian. If you are at all concerned about a reaction with a Novartis product please see your veterinarian. (In the same way that some humans are unable to tolerate a relatively mild drug like ASA, some pets may be sensitive to a component of Fortekor and may get the equivalent of an upset stomach). Ensuring the dose is given after the full meal is one way to relieve this (although it is not necessary for the dose to be effective). Sometimes direct dosing of a dog with a tablet (forcing it directly down the throat) can stimulate the gag reflex and cause vomiting, which is unrelated to the drug itself. If this occurs repeatedly, you will need to alter your dosing method, such as mixing the dose with a meal.
In the days after the dose is started, it is not unusual for the dog to suffer an increased need to urinate. The action of Fortekor on the RAA system causes the body to stop its absorption of salt and water that was previously caused by the heart disease. If applicable, reducing the dose of a concomitant diuretic, under the recommendation and supervision of a veterinarian, may clear up this effect. If the dog is not on any other drugs it should clear up within a few days as the body normalizes its water and sodium retention after the cardiac output is improved.
Although more rare than in dogs, heart disease does occur in cats. (Using Fortekor in cats is considered off label and should be sought only at the recommendation of a veterinarian, but there is data to show that is effective in inhibiting ACE). Your veterinarian will be able to provide you with more information.
All ACE inhibitors have similar pharmacodynamic properties with certain differences in elimination of the drug. Older ACE inhibitors excrete 95% of the drug through the kidney, which may further complicate a dog suffering from renal failure. Stricter monitoring properties are needed for the older ACEI’s. No dosage adjustment is necessary with Fortekor in dogs with impaired renal function.
Fortekor has not been tested on pregnant dogs. Its use in such dogs must be decided on by a risk/benefit ratio by the veterinarian.
As a prescription drug, Fortekor is only available through your veterinarian. All suggested dosage information and recommendations must come from the veterinarian. Any change in dosage, or any problems encountered by the owner when treating with Fortekor should be reported to your veterinarian immediately.
Thanks to its dual excretion and single daily dosing, convenience and safety are the primary benefits Fortekor offers to you and your dog. Which means you are able to spend more quality time with your dog, with less worry, and your dog will lead a longer, happier life.