Comparative palatability of a new formulation and two commercial formulations of benazepril

Comparative palatability of a new formulation and two commercial formulations of benazepril in dogs C. ZEMIRLINE 1 *, J. BERANGER 1, S.GOBBI 2 and E. CISSAY 3 1 SOGEVAL Laboratories, Research and Development Department, Parc Technopole, BP 96105, Avenue Pierre de Coubertin, 53061 Laval Cedex 9, FRANCE. 2 SOGEVAL Laboratories, Pet Business Unit, BP 2227, 200 avenue de Mayenne, 53061 Laval Cedex 9, FRANCE. 3 BIO 2M, Domaine des Souches, 89130 Mézilles, FRANCE. *Corresponding author: claudine.zemirline@sogeval.fr SUMMARY Poor compliance in long-term treatments may be a major obstacle to therapeutic success even when using the most effective of drugs. In the case of oral medication, palatability plays a significant role in dosing compliance. NELIO 20 tablets is a new benazepril formulation indicated for the long-term treatment of heart failure in dogs, and the authors considered it important to evaluate its palatability in comparison with two commercial formulations already available on the market: FORTEKOR 20 tablets and BENAKOR 20 tablets. Acceptance and preference tests were therefore performed in 20 dogs to compare the voluntary acceptance, preference and consumption of the three products. The acceptance tests showed a spontaneous prehension rate of 100% for NELIO 20 and FORTEKOR 20, and 90% for BENAKOR 20. Full consumption after prehension took place in 90% of the tests with NELIO 20 compared to 95% of those with FORTEKOR 20 (p > 0.05) and 50% of those with BENAKOR 20 (p < 0.02). No preference was observed between NELIO 20 and FORTEKOR 20 (p > 0.05) while 63% of the dogs chose NELIO 20 instead of BENAKOR 20 (p < 0.02). These results suggest that NELIO 20 could be an interesting alternative that may improve dosing compliance and therefore the therapeutic effects in the longterm treatment of heart failure. Keywords: Palatability, compliance, treatment of heart failure, benazepril, dog. RÉSUMÉ Comparaisons d appétence entre une nouvelle formulation et deux formulations commerciales de benazepril chez le chien Indépendamment de l'efficacité du produit utilisé, la non-observance des traitements à long terme peut être un obstacle majeur au succès thérapeutique. En cas d'administration orale d'un médicament, l'appétence joue un rôle significatif dans l'observance thérapeutique. Etant donné que NELIO 20 comprimés est une nouvelle formulation de bénazépril indiquée pour le traitement au long cours de l'insuffisance cardiaque chez les chiens, les auteurs ont jugé important d'évaluer son appétence par rapport à celle de deux formulations commerciales déjà disponibles sur le marché, FORTEKOR 20 comprimés et BENAKOR 20 comprimés. Des tests d'acceptabilité et de préférence ont été menés chez 20 chiens afin de comparer l'acceptabilité, la préférence et la consommation volontaires des trois produits. Dans les tests d'acceptabilité, le taux de prise spontanée a été de 100 % pour NELIO 20 et FORTEKOR 20, et de 90 % pour BENAKOR 20. Après la prise, une consommation complète a été observée dans 90 % des tests pour NELIO 20, par rapport à 95 % des tests pour FORTEKOR 20 (p > 0,05) et à 50 % des tests pour BENAKOR 20 (p < 0,02). Aucune préférence n a été observée entre NELIO 20 et FORTEKOR 20 (p > 0,05) alors que 63 % des chiens ont choisi NELIO 20 plutôt que BENAKOR 20 (p < 0,02). Ces résultats tendent à démontrer que NELIO 20 devrait être une alternative intéressante pour améliorer l'observance thérapeutique, et par conséquent les effets thérapeutiques attendus dans le traitement à long terme de l'insuffisance cardiaque. Mots clés : Appétence, observance, traitement de l insuffisance cardiaque, benazepril, chien. Introduction The clinical benefits of angiotensin-converting enzyme (ACE) inhibitors in heart failure have been well documented in canine studies. In general, ACE inhibitors improve clinical signs and improve quality of life in dogs with heart failure due to diverse causes [4]. The clinical effects observed with such drugs are clearly due to their mechanism of action as their inhibition of ACE decreases blood levels of angiotensin II and aldosterone. As a result, ACE inhibitors cause arterial vasodilatation, and decrease systemic blood pressure, increase cardiac output and reduce heart rate [2]. Of the five different ACE inhibitors that have been used in dogs, benazepril is considered to offer the longest duration of action [4]. Indeed, repeated dose pharmacokinetic studies have shown that benazepril continues to exert 85% inhibition on ACE activity 24 hours after administration in dogs [6]. This pharmacokinetic profile allows doses of 0.23 mg/kg of benazepril to be administered only once daily. Due to the severity of their dog s condition and the possible dramatic outcome if no care is provided, owners are acutely aware of the need for treatment in early-diagnosed heart failure. However, such a treatment will often be life-long. Therefore, besides owner motivation, ease of administration should also be taken into consideration to ensure dosing compliance. Benazepril is only available for oral administration. This underlines the advantages of palatable tablets which facilitate daily administrations in the long-term treatment of heart failure.

276 ZEMIRLINE (C.) AND COLLABORATORS Since no guidelines for palatability studies are available, and in order to provide as much accurate information as possible regarding animal behaviour when products are offered either separately or simultaneously, the design and procedures of the studies reported in this paper were derived from those used in the pet food industry [10]. Similar methodologies were described in a recent paper reporting on the palatability of NSAIDs [7, 8]. The aim of this study was to compare the palatability of a new formulation of benazepril with those of two commercially available formulations of the same compound. Materials and Methods The palatability of NELIO 20 (18.42 mg benazepril per tablet, Sogeval) was compared with that of FORTEKOR 20 (18.42 mg benazepril per tablet, Novartis Animal Health) and BENAKOR 20 (18.42 mg benazepril per tablet, Virbac) by means of acceptance and preference tests for each comparison. In all tests, each dog was offered a half tablet of each product, whether separately (in acceptance tests) or simultaneously (in preference tests) and independently of animal weight. Here it was considered more relevant to test the palatability of the same dosing unit for all products (i.e. half a tablet) even if some dogs received a higher dose than that recommended for therapy (the mean (± SD) dose was 0.61 (± 0.28) mg/kg with a minimum of 0.27 mg/kg and a maximum of 1.02 mg/kg). Since up to 200-fold overdosing with benazepril in the normal dog is asymptomatic, the overdoses administered in these studies, i.e. up to 4 fold the recommended therapeutic dose, were therefore well within the safety margin [1]. The preference tests were performed first over a six-day period followed by the acceptance tests over a three-day period, with a four-day washout period between the two. Temperature and hygrometry were measured daily, but were not controlled throughout the study. STUDY SITE DESCRIPTION All the acceptance and preference tests reported in this paper were conducted at the same private laboratory. The animals were housed in individual pens on dust-free woodshaving litter in approved facilities by the French Ministry of Agriculture and Fisheries. The dogs were fed ad libitum with a complete and balanced diet for dogs (Moppy kibbles 24/10) and had unrestricted access to drinking water. The dogs were acclimatized before the start of the study. receive any treatments in the course of the studies which could have interfered with the appetite of the animals. PREFERENCE TESTS Each of the 20 dogs was simultaneously offered a pair of products, i.e. NELIO 20 and FORTEKOR 20 or NELIO 20 and BENAKOR 20, once a day on six separate days between D0 and D5. Each product pair was offered on three occasions to each dog according to the randomised allocation plan given in Table I. The randomization was done using a table of random permutations of 9 numbers [3]. The tests were blinded since the products could not be identified by the operator. In all 120 preference tests one half tablet of each assigned product pair was placed on the floor inside the animal s pen either in a bowl or - for dogs afraid of the bowl or likely to play with it- directly on the ground after having pushed the litter away. The two products in each preference test were randomly assigned to the right and left bowls, or to the right and left sides of the technician when the products were placed directly on the ground. The distance between the bowls was approximately the same (20 cm) in each test. When the products were on the ground, the technician drew the dog s attention to the half tablets, stepped back and started a timer. As soon as the first product entered the dog s mouth, the timer was stopped and the prehension time, i.e. the time elapsed between the dog first noticing the two products and taking one of the products into its mouth, was recorded. If after 60 seconds the dog had not taken either of the products or if it had taken one of the products then partially or totally spat it out, the two products were again offered simultaneously in the hollow of, or with the fingers of, the right or left hand, depending to the previous allocation of each product in the bowl or on the ground. A further 60 seconds were allowed for the dog to take one of the two products into its mouth. If after these further 60 seconds the dog had taken neither of the products, the test was terminated. Each time a product entered the dog s mouth, consumption was assessed as full if the dog fully swallowed the half tablet, partial if the dog partially swallowed the half tablet and spat some out, and none if the dog completely spat out the half tablet. All preference tests were performed by the same experienced technician between 8 and 10 a.m. every day. The products were handled with different tweezers. When possible, the dog was not permitted to take the second product after the first product had been taken. Between the tests, the bowl was cleaned with kitchen wipes and the technician's hands were washed with water. ANIMALS Twenty adult healthy dogs (10 Beagles and 10 Golden Retriever crosses provided by BIO 2M) of either sex and familiar with the procedures of palatability tests run with tablets of pharmaceutical products, were used. The mean ± SD body weight of the dogs at study initiation was 18.9 (± 8.96) kg ranging from 9.0 to 34.2 kg, and mean age was 1.9 (± 0.92) years ranging from 0.77 to 3.94 years. All had been vaccinated and wormed prior to study start, and did not ACCEPTANCE TESTS The 20 dogs were offered one half tablet of NELIO 20, FORTEKOR 20 or BENAKOR 20, once a day on three separate days: D0, D1 and D2. Each product was offered on only one occasion to each dog according to a randomised allocation plan which is detailed in Table II. The randomization was done using a table of random permutations of 9 numbers [3]. The tests were blinded since the products could not be identified by the operator.

PALATABILITY OF BENAZEPRIL FORMULATIONS 277 Treatment* Dogs Day 0 Day 1 Day 2 Day 3 Day 4 Day 5 Right Left Right Left Right Left Right Left Right Left Right Left ** ** ** ** ** ** ** ** ** ** ** ** 1 A B C A B A A C A B C A 2 C A A B A C B A C A A B 3 C A B A A C A B C A B A 4 B A A C A B C A B A A C 5 A B C A B A A C A B C A 6 A C A B C A B A A C A B 7 A B A C B A C A A B A C 8 C A A B A C B A C A A B 9 B A C A A B A C B A C A 10 A C A B C A B A A C A B 11 A C B A C A A B A C B A 12 A B A C B A C A A B A C 13 B A A C A B C A B A A C 14 A C B A C A A B A C B A 15 B A C A A B A C B A C A 16 C A A B A C B A C A A B 17 B A A C A B C A B A A C 18 C A B A A C A B C A B A 19 A B A C B A C A A B A C 20 A C B A C A A B A C B A * Treatment A: NELIO 20, Treatment B: FORTEKOR 20, Treatment C: BENAKOR 20 ** Right: product randomly assigned to the right bowl; Left: product randomly assigned to the left bowl TABLE I: Study design and randomised allocation plan for the preference tests. Each of the 20 dogs was simultaneously offered a pair of products, i.e. NELIO 20 and FORTEKOR 20 or NELIO 20 and BENAKOR 20, once a day on six separate days between Day 0 and Day 5. Each product pair was offered on three occasions to each dog according to the randomised allocation plan above. Treatment* Dogs Day 0 Day 1 Day 2 1 A B C 2 B C A 3 C A B 4 B A C 5 A C B 6 C B A 7 C A B 8 B C A 9 A B C 10 B A C 11 A C B 12 C B A 13 C A B 14 A B C 15 B C A 16 C B A 17 A C B 18 B A C 19 A B C 20 C A B * Treatment A: NELIO 20, Treatment B: FORTEKOR 20, Treatment C: BENAKOR 20 TABLE II: Study design and randomised allocation plan for the acceptance tests. The 20 dogs were offered one half tablet of NELIO 20, FORTEKOR 20 or BENAKOR 20, once a day on three separate days: Day 0, Day 1 and Day 2. Each product was offered on only one occasion to each dog according to the randomised allocation plan above.

278 ZEMIRLINE (C.) AND COLLABORATORS The procedures were similar as those used for preference tests except that only one tested formulation was offered. All acceptance tests were performed by the same experienced technician at about 8.30 a.m., every day. Statistical analysis The dog was considered as the experimental unit in all statistical analyses. Mean prehension time was determined for each product in both the acceptance and preference tests. Analysis of the data was performed using Statgraphics Plus 5.1 and Excel (Microsoft) computer programs. PREFERENCE TESTS The preferred product was determined for each dog as follows: if the dog chose product A more times than product B, it was said to have expressed a preference for product A and vice versa. If the dog chose each product an equal number of times, it was said to have expressed no preference. The number and percentage of dogs (100*(the number of dogs preferring product A or B / the total number of dogs showing a preference)) preferring each product was calculated and a Chi-Square test was performed to compare the percentage of dogs preferring NELIO 20 versus FORTEKOR 20 and NELIO 20 versus BENAKOR 20 at the 5% level of statistical significance. The number and percentage of tablets swallowed was also determined for each product. ACCEPTANCE TESTS The number and percentage of dogs that took and swallowed the product was determined for each product. McNemar s test was used to detect any differences in full consumption between NELIO 20 and FORTEKOR 20 and between NELIO 20 and BENAKOR 20 at the 5% level of statistical significance. Results No abnormal behaviour or health problems were reported during the studies except for three dogs that showed soft faeces or diarrheoa (two dogs on D1 in the acceptance tests and one dog on D4 in the preference tests). No relation between these clinical signs and test procedures or product was established. Under uncontrolled environmental conditions, temperature varied from 8.2 C to 24.3 C, and hygrometry varied from 23% to 83% throughout the studies. PREFERENCE TESTS NELIO 20 versus FORTEKOR 20 Out of the 60 preference tests performed, NELIO 20 was chosen 27 times (45%), FORTEKOR 20 was chosen 26 times (43%) and no choice was made in 7 tests (12%) (Figure 1a). In all the tests where the products were taken into the mouth, this occurred from the bowl or from the ground. In the 7 tests where no choice was made, the two products were offered to the dogs by hand, but were not taken. Nineteen dogs out of 20 expressed a preference for one of the two products: 11 dogs (58%) preferred NELIO 20 and 8 dogs (42%) preferred FORTEKOR 20. This difference was not statistically significant. Out of the 27 tests where NELIO 20 was taken, it was fully consumed on 24 occasions (89%) and not consumed on 3 occasions (11%). FORTEKOR 20 was in all cases fully consumed when taken (Figure 1b). In the three tests where NELIO 20 was taken then completely spat out, the two products were offered again to the dogs by hand, but neither of the two products was taken. Mean prehension time was 4.81 (± 5.09) seconds and 5.12 (± 5.46) seconds for NELIO 20 and FORTE- KOR 20, respectively. There was no statistically significant difference between the two mean prehension times. NELIO 20 versus BENAKOR 20 Out of the 60 preference tests performed, NELIO 20 was chosen 30 times (50%), BENAKOR 20 was chosen 22 times (37%) and no choice was made in 8 tests (13%) (Figure 2a). In all the tests where the products were taken into the mouth, this occurred from the bowl or from the ground. In the 8 tests where no choice was made, the two products were offered to the dogs by hand, but were not taken. Sixteen dogs out of 20 expressed a preference for one of the two products: 10 dogs (63%) preferred NELIO 20 and 6 dogs (38%) preferred BENAKOR 20. This difference was statistically significant (p < 0.02). Out of the 30 tests where NELIO 20 was taken, it was fully consumed on 26 occasions (87%) and not consumed on 4 occasions (13%). Out of the 22 tests where BENAKOR 20 was taken, it was fully consumed on 8 occasions (36%), partially consumed on one occasion (5%) and not consumed on 13 occasions (59%) (Figure 2b). In the 4 tests where NELIO 20 was taken then completely spat out, the two products were offered again to the dogs by hand, but neither of the two products was taken. In the 13 tests where BENAKOR 20 was taken then completely spat out, the two products were offered again to the dogs by hand. NELIO 20 was then chosen and taken from the hand and totally consumed in 4 of these 13 tests. Mean prehension time was 3.33 (± 12.23) seconds and 3.27 (± 7.35) seconds for NELIO 20 and BENAKOR 20, respectively. There was no statistically significant difference between the two mean prehension times. ACCEPTANCE TESTS A total of 60 acceptance tests were therefore conducted over three consecutive days. Out of the 20 dogs, 20 (100%) took NELIO 20 from the bowl or from the ground, 20 (100%) took FORTEKOR 20 from the bowl or from the ground, and 18 (90%) took BENAKOR 20 (17 (85%) from the bowl or from the ground and 1 (5%) from the hand) (Figure 3a). Of the 20 dogs that took one half tablet of NELIO 20, 18 (90%) fully consumed the product and 2 (10%) did not consume the product. Of the 20 dogs that took

PALATABILITY OF BENAZEPRIL FORMULATIONS 279 one half tablet of FORTEKOR 20, 19 (95%) fully consumed the product and 1 (5%) did not consume the product. Of the 20 dogs that took one half tablet of BENAKOR 20, 9 (50%) fully consumed the product, 2 (11%) partially consumed the product and 7 (39%) did not consume the product (Figure 3b). Full consumption was not statistically significant between NELIO 20 and FORTEKOR 20, but was statistically significant between NELIO 20 and BENAKOR 20 (p < 0.02). Mean prehension time was 2.55 (± 2.26) seconds, 5.20 (± 8.13), and 2.83 (± 2.71) seconds for NELIO 20, FORTEKOR 20 and BENAKOR 20, respectively. There were no statistically significant differences for mean prehension time between NELIO 20 and FORTEKOR 20, or between NELIO 20 and BENAKOR 20. Considering all products together, out of the dogs that partially or totally spat out the half tablet after having taken it from the bowl or from the ground, only 3 took the product again from the hand, and only one totally consumed the product. These latter observations all concerned BENAKOR 20. FIGURE 1A: NELIO 20 vs FORTEKOR 20 palatability comparison in preference tests Choice of products. FIGURE 1B: NELIO 20 vs FORTEKOR 20 palatability comparison in preference tests - Consumption of prehended products. FIGURE 2A: NELIO 20 vs BENAKOR 20 palatability comparison in preference tests Choice of products. FIGURE 2B: NELIO 20 vs BENAKOR 20 palatability comparison in preference tests - Consumption of prehended products. FIGURE 3A: NELIO 20 vs FORTEKOR 20 and BENAKOR 20 palatability comparison in acceptance tests Prehension of products. FIGURE 3B: NELIO 20 vs FORTEKOR 20 and BENAKOR 20 palatability comparison in acceptance tests - Consumption of prehended products.

280 ZEMIRLINE (C.) AND COLLABORATORS Discussion In the acceptance tests, all three products were spontaneously taken from the bowl or from the ground by over 90% of the dogs, and except for one case, concerning BENAKOR 20, it was not necessary to offer the products by hand. NELIO 20 gave good prehension and consumption results in all the palatability tests. None of the dogs refused NELIO 20 in the acceptance tests, and no preference (p>0.05) was observed between NELIO 20 and FORTEKOR 20. However, NELIO 20 was preferred over BENAKOR 20 in 63% of the dogs (p<0.02). The full consumption rate for NELIO 20 was identical and high (around 90%) in both the acceptance and preference tests. Although the tests were performed on a small number of animals and under experimental conditions, the results tend to suggest that NELIO 20 should be easy to administer since the dogs should voluntary take it and fully consume it in most cases. The results of these tests show that the palatability of NELIO 20 is similar to that of FORTEKOR 20, with no refusals in the acceptance tests and a full consumption percentage exceeding 90% in all tests. BENAKOR 20 showed the poorest palatability in these tests. Even if the percentage of dogs taking the product was high in the acceptance tests, its full consumption rate was low, ranging from 36% to 50% in all tests. So in real conditions, the dogs should readily take the product but swallow it in less than 50% of cases. There was no statistically significant difference for mean prehension time between NELIO 20 and the two other products. But, even if the speed with which an animal accepts a product is sometimes considered as a measure of the palatability of pharmaceutical products, full consumption should be considered to be of primary importance since it is a direct measure of compliance [11]. Since the aim of this study was to compare the palatability of the new formulation of benazepril (NELIO 20) with those of two commercially available formulations of the same compound (FORTEKOR 20 and BENAKOR 20), the 2x2 cross-over design used in the preference tests did not include the pair comparison FORTEKOR 20 versus BENAKOR 20. In the acceptance tests, the number of dogs for a sequence of administration (ABC or BCA or CBA) was not the same, and even if the sequence of product administration was randomized, a potential sequence effect may have been possible. This kind of effect was however not taken into account in the statistical model. The environmental conditions were not strictly controlled throughout the study and it is not possible to discard that their variations may have affected the result between testing periods. In dogs used to run palatability tests with tablets of pharmaceutical products, as those used in these studies, an overestimation of the actual overall acceptance rate for the tested products seems to be a low risk. Indeed, it has been described that dogs used to flavour changes show more stable preferences [5]. Furthermore, even if the acceptance tests may be closer to the owner concern, it has been demonstrated that preference tests are more sensitive since the animals can exercise their choice [10]. For the same reasons, and since all three products were tested on the same way, the order in which the tests were run (in our studies, the preference tests were performed before the acceptance tests), as well as the duration of the wash-out period may have a low incidence on the results. The breed model used in these studies is not conventional as most of palatability studies are performed with Beagles. However, by now, no standard or widely recognised procedures have been described for assessing the palatability of pharmaceutical products. Even in the pet food industry, no breed recommendations have been made. The studies presented in this paper were run with Beagles and Golden Retriever crosses, and allow taking into consideration two different species instead of only one. In our studies, the option was made to run acceptance and preference tests on the same dogs, instead of using separate groups of dogs. Recent published papers [7, 8] report similar studies including also acceptance and preference tests run on the same dogs. Since the aim of these studies was to evaluate the palatability of one unique experimental unit, the same for all three tested products (i.e. one half tablet), it would not have been relevant to compare different dosages between tested products. Indeed, it has been established that the form, the size and the texture of the tablet may have an impact on palatability in dogs. Therefore, the recommended dose level was not respected for all dogs. The term palatability is usually employed to describe how well a dog likes the taste of a pharmaceutical product, but in the same manner as for pet foods, other characteristics such as its appearance, aroma, flavour and texture certainly also play a role. The tests reported in this paper did not intend to explain the reasons and mechanisms behind the behaviour of the animals, but only to provide a rigorous evaluation of the prehension, preference and consumption of NELIO 20 and two other benazepril formulations. Both acceptance and preference tests were performed to gather as much accurate information as possible since they provide complementary data. Whereas in one-pan intake tests, the animal s response to a given product was being tested, in the two bowls test, the animal s choice was forced, and the preference for one product over another was evaluated. Also, since it had been demonstrated in previous studies that some animals may show a side preference, the bowls were randomly rotated on a daily basis in the preference tests, so that product A was on the left side on day 1 but on the right side on day 2 [9]. The preference tests assessed individual dog preferences rather than the average preference for all dogs as it has frequently been observed in such tests that some dogs are quite different in terms of their preferences from the majority of the dogs in the panel [12]. Finally, 20 dogs and at least two days were reported in previous publications to be sufficient when determining palatability differences between any two food samples with sufficient accuracy and efficiency [12]. In conclusion, even if it is recognised that palatability involves an interaction between the pet, the product and the environment, and that assessing an animal s behaviour towards a product in their own home should typically follow kennel tests and represent a final stage in product evaluation, these tests pro-

PALATABILITY OF BENAZEPRIL FORMULATIONS 281 vide a fair evaluation of palatability under experimental conditions. Conclusion These acceptance and preference tests showed that NELIO 20, a new formulation of benazepril, was as palatable as FORTEKOR 20 and more palatable than BENA- KOR 20. NELIO 20 was systematically taken into the mouth by the dogs, and totally consumed in 90% of cases. No preference (p>0.05) was observed between NELIO 20 and FORTEKOR 20, but NELIO 20 was more often preferred by the dogs than BENAKOR 20 (p<0.02). In diseases that require long-term treatment, e.g. heart failure, the chosen drug should be efficient and safe. But, it is also of primary importance that it be easy and convenient to administer, thereby ensuring dosing compliance. NELIO 20 is therefore an interesting formulation to improve owner s compliance in the management of dogs with congestive heart failure. References 1. - ANONYMOUS. Fortekor 20: Summary of Product Characteristics (UK) In: Veterinary Medicines Directorate, ed. London: Co-ordination Group for Mutual Recognition and Decentralised Procedures - Veterinary (CMD(v)), 2004,1-2, 72 (Website: www.vmd.gov.uk/espcsite/documents/124047.doc) 2. - BOOTHE D.: Therapy of cardiovascular diseases. In: R. KERSEY, D. KILMER (ed): Small animal clinical pharmacology and therapeutics, 1 st ed. Philadelphia, W.B. Saunders company, 2001, 565-566. 3. - COCHRAN W., COX G.: Experimental designs. Wiley, New York, 1957. 4. - GORDON S., KITTLESON M.: Drugs used in the management of heart disease and cardiac arrhythmias. In: MADDISON J., PAGE S.W., CHURCH D.B. (ed): Small animal clinical pharmacology, second edition ed. Philadelphia, Elsevier, 2008, 412-418. 5. - GRIFFIN R.W., SCOTT G. C., CANTE C.J.: Food preferences of dogs housed in testing-kennels and in consumers homes: some comparisons. Neurosci. Behav. Rev., 1984, 8, 253-259. 6. - KING J.N., MAURER M., MORRISON C.A., MAURON C., KAISER G.: Pharmacokinetics of the angiotensin-converting-enzyme inhibitor benazepril, and its active metabolite, benazeprilat, in dog. Xenobiotica, 1997, 27, 819-829. 7. - PAYNE-JOHNSON M., MAITLAND T.P., BULLARD J., GOSSELLIN J.: Comparative palatability of three commercial formulations of carprofen and one commercial formulation of firocoxib in dogs. Revue Méd. Vét., 2006, 157, 1-10. 8. - PAYNE-JOHNSON M., MAITLAND T.P., TILT N., GOSSELLIN J.: An evaluation of the relative palatability of two commercial oral tablet formulations of carprofen and meloxicam in dogs using acceptance and preference tests. Revue Méd. Vét., 2007, 158, 519-524. 9. - ROFE P.C., ANDERSON R.S.: Food preference in domestic pets. Proc. Nutr. Soc., Cambridge University Press, 1970, 29, 330-335. 10. - THOMBRE A.G.: Canine acceptability of flavoured placebo tablets. 29. Proc. Int. Symp. Control. Release Bioact. Mater., 2002, 116. 11. - THOMBRE A.G.: Oral delivery of medications to companion animals: palatability considerations. Adv. Drug Delivery Rev., 2004, 56, 1399-1413. 12. - WATERHOUSE H.N., FRITSCH C.W.: Dog food palatability tests and sources of potential bias. Lab. Anim. Care, 1967, 17, 93-102.