The Efficacy, Tolerance and Safety of the Angiotensin Converting Enzyme Inhibitor Ramipril in Cats With Cardiomyopathy with or without Hypertension
*Tierärztliche Klinik J.-F. und A.-U. Schille
Angiotensin converting enzyme (ACE) inhibitors have long been recognized as an effective treatment for heart insufficiency in human and canine medicine and for human hypertension. However, only a few studies have been carried out to date on the use of ACE inhibitors in cats. This group of drugs was administered to hypertensive and normotensive cats suffering from hypertrophic cardiomyopathy (HCM) in the present study. The aim of this study was to evaluate the effectiveness, tolerance levels and safety of the ACE inhibitor ramipril in cats.
Fifty-four cats suffering from heart disorders were monitored and the course of their illness was documented for periods ranging from 2 months to 2 years. The cats were treated either with ramipril (Vasotop®, Intervet International) alone or in combination with the loop diuretic furosemide. Ramipril treatment was administered at the dose rate recommended for use in dogs (0.125 mg/kg bodyweight once daily).
Initially a general examination, followed by specific cardiological examinations including blood pressure monitoring, radiological examinations, electrocardiograms and echocardiograms and blood screening were carried out. An overview of the clinical signs, obtained from the cardiological examinations, in these cats with heart disorders is presented. Secondly, the clinical findings from the initial examinations are compared with the results of control examinations and thus the effectiveness of ramipril is documented. Various blood values and the blood pressure were monitored in order to detect possible side effects of ramipril.
Twenty-six of the 54 cats (48%) treated were diagnosed as having hypertension (systolic blood pressure: 180-300 mmHg) and myocardial hypertrophy (Group A). Twenty-two cats (41%) were normotensive but suffered from HCM (Group B). Four of the remaining 6 cats (7%) showed signs of hyperthyroidism and 2 cats (4%) had dilated cardiomyopathy (Group C). Only one of these cats had concomitant hypertension.
Thirteen cats (24%) were treated with ramipril only while the majority (n=41, 76%) received combined therapy (ramipril plus a loop diuretic). The clinical signs in the cats improved with treatment. While normotensive cats did not show a significant blood pressure decrease, a decrease in blood pressure could be measured in the hypertensive cases. Regression of existing cardiomyopathy could not be evaluated statistically. However, one of the echocardiographic parameters improved in 54.1% of cats in the present study.
There was no consistent trend in the serum chemistry parameters relating to renal function: these increased in some cats and decreased in others. Due to the infrequent occurrence of side effects, ramipril treatment did not have to be discontinued in any of the cases in the present study.
Ramipril treatment was combined with thyrostatic treatment (carbimazole) in cats suffering from hyperthyroidism, and both drugs proved to be effective and did not produce side effects. This also applied to the combination of ramipril and ß-methyldigoxin in cats with dilated cardiomyopathy.
The dose rate of ramipril recommended for dogs (0.125 mg ramipril/kg once daily) proved to be adequate in most cases and improved the clinical signs in the cats in the present study. In the present study, side effects occurred infrequently in the cats and did not require ACE inhibitor treatment to be stopped on any occasion. Ramipril treatment not only appeared to be safe in combination with the loop diuretic furosemide but also with the thyrostatic drug carbimazole and with ß-methyldigoxin in the cats in the present study.