Effects of Dexamethasone, Metoclopramide or Acepromazine on Emesis in Cats Sedated with Xylazine Hydrochloride

Topal A. , N. Y. Gül: Effects of Dexamethasone, Metoclopramide or Acepromazine on Emesis in Cats Sedated with Xylazine Hydrochloride. Acta Vet. Brno 2006, 75: 299-303. This study was designed to determine antiemetic efficacy of prophylactic administration of dexamethasone, metoclopramide or acepromazine and their influence on sedation in cats sedated with xylazine hydrochloride. Ten healthy adult cats (5 males and 5 females) were used. The prophylactic antiemetic effects of dexamethasone (4 mg/kg of body weight, IM), metoclopramide (0.4 mg/kg of body weight, IM), acepromazine (0.1 mg/kg of body weight, IM) or saline (0.9% NaCI) solution (0.1 ml/kg, IM) administered 1 hour before administration of xylazine hydrochloride (2 mg/kg, IM) was evaluated. Initially, the cats were given saline treatment (day 0); sequentially they were given dexamethasone, metoclopramide or acepromazine at 1 week intervals. After a xylazine injection, all cats were observed for 90 minutes for the assesment of frequency of emesis, and the time until the onset of the first emetic episode, and the determination of xylazine-induced sedation time. Prior treatment with 4 mg/kg of dexamethasone significantly reduced the frequency of emetic episodes but no alteration was observed in the time until the onset of the first emetic episode after the xylazine injection. Metoclopramide and acepromazine did not alter the frequency of emetic episodes but metoclopramide significantly prolonged the onset of the first emetic episode. Dexamethasone (4 mg/kg, IM) significantly decreased the frequency of emetic episodes without affecting the time until the onset of the first emetic episode, xylazine-induced sedation in cats. Antiemetic drugs, antiemetic effects, emetic episodes, sedation Xylazine hydrochloride is widely used in biological and veterinary medical research as a sedative analgesic restraining agent. It is known that xylazine induces vomiting within a few minutes of systemic injection in cats and dogs (Ho et al. 2001; Hikasa et al. 1986; Hikasa et al. 1992a; Hikasa et al. 1992b; Colby et al. 1981). Xylazine has been shown to evoke vomiting through its actions on the emetic chemoreceptor trigger zone (CTZ) of the area postrema in cats (Colby et al. 1981; Hikasa et al.1992a; McCarthy and Borison 1984) and dogs (Hikasa et al. 1986). It has been shown that, both in cats (Colby et al. 1981; Hikasa et al. 1989; Hikasa et al.1992a) and dogs (Hikasa et al.1986; Hikasa et al.1992b), the emetic action of xylazine injected intramuscularly is mediated through α2-adrenoceptors, because this effect of xylazine is prevented only by α2-adrenoceptor antagonists, such as yohimbine, tolazoline, and phentolamine (Hikasa et al. 1989; Hikasa et al. 1992a). On the other hand, recent studies have suggested that glucocorticoids, such as dexamethasone, may be involved in the control of vomiting induced by xylazine acting on the area postrema (Ho et al. 2001). Dexamethasone is a glucocorticoid that is effective in preventing chemotherapy-induced emesis in humans (Jones et al.1991; Spector et al. 1998; Wang et al.1999), cats (Rudd et al. 2000), dogs (Fukui and Yamamoto 1999), ferrets (Hawthorn and Cunningham 1990; Rudd and Naylor 1996), and pigeons (Tanihata et al. 2000). ACTA VET. BRNO 2006, 75: 299–303 Address for correspondence: Assoc. prof. Dr. Ayse Topal Department of Surgery Faculty of Veterinary Medicine, Uludag University 16190 Bursa, Turkey Phone: + 90 224 2 347 655 Fax : + 90 224 2 346 395 E-mail: [email protected] http://www.vfu.cz/acta-vet/actavet.htm Other studies have reported the antiemetic potential of phenothiazine in cats (McCarthy and Borison 1984) and metoclopramide in dogs (Hikasa et al. 1986). Xylazine has been widely used as a sedative in animals prior to performing many procedures, such as radiography, catheterization, and ultrasonography. However, emesis is frequently reported after xylazine administration in cats, which may distress the animal and also increase the risk of aspiration pneumonia. Centrally acting drugs are more effective than peripherally acting drugs. Phenothiazine derivates (e.g. acepromazine) and metoclopramide inhibits the chemoreceptor trigger zone and increases gastric tone and peristalsis, both of which inhibit emesis (Hikasa et al. 1992a). On the other hand, only one study reported that pre-treatment with dexamethasone (4 or 8 mg/kg, IM) decreased the number of emesis and prolonged latency of xylazine induced emesis in cats (Ho et al. 2001). The present study was conducted on cats to determine which of these three drugs have an antiemetic effect on xylazine-induced emesis. Materials and Methods Animals Healthy adult mixed-breed cats (5 males and 5 females) weighing from 2.3 to 4.5 kg (median, 3.8 ± 0.5 kg) were used for the study. Prior to the experiment they were sheltered individually in stainless-steel cages in an airconditioned room controlled at 22 ± 2 °C. All cats in each experiment were fed commercial dry food and water ad libitum and fasted for 12 h before the emetic experiment. All experiments were conducted in accordance with the Animal Research Ethics Committee of the Uludag University of Turkey. Experimental per iods Adminis t rat ion of drugs The antiemetic effects of dexamethasone, metoclopramide or acepromazine and saline (0.9% NaCI) solution given IM 1 hour before IM administration of xylazine were evaluated. Antiemetic drugs were injected in the semitendinous muscle of one leg. All cats were subjected to the same procedures, and each treatment was performed at a 1 week interval. On the first day, the cats were given saline solution (0.1 ml/kg of body weight, IM), and on days 7, 14 and 21, they were given dexamethasone (4 mg/kg, IM), metoclopramide (0.4 mg/kg, IM), and acepromazine (0.1mg/kg, IM). Immediately after these injections, the cats were fed 100150 g commercially produced dry food. One hour later, each cat was administered xylazine (2 mg/kg, IM) in the semitendinous muscle of the other leg. The dosage was chosen on the basis of the effective dose to induce sedation on cats. The cats were observed until the end of the sedative effect, according to Lerche et al. (2002). During this period, the time until the onset of the first emetic episode, the frequency of emesis, and the time until the onset of the sedative effect and sedation period were determined. The effects of these drugs on xylazine-induced sedation were evaluated. Drugs Used The drugs used and their sources were as follows; xylazine HCI (Rompun®, 2%, Bayer Company, Leverkusen, Germany), dexamethasone sodium phosphate (Onadron®, 4 mg/ml, I.E.Ulagay Company, Istanbul, Turkey), metoclopramide HCI ( Metpamid®, 1 mg/ml, Sifar Company, Istanbul, Turkey), acepromazine (Vetranquil®, 1%, Sanofi, Paris, France). All doses were calculated on the basis of the drug base weight. All drugs were used as undiluted solution. Emetic response Emesis was scored as an “all or none” response; separate episodes of emesis were considered when the interval between bouts of vomiting exceeded 10 seconds. During the observation period after the injection of xylazine, the number of emetic episodes was counted. The time until the onset of the first emetic episode was recorded. The beginning of a sedative response was recorded when the cat assumed sternal or lateral recumbency and was unable to stand. The time until the onset of sedation after administration of xylazine was recorded. Also the end of the sedative effect was recorded when the cat was able to stand and walk without aid. Stat is t ical Analysis All data were reported as mean ± SD. Data for the time until the onset of sedation and the sedation period, latency of emesis, frequency of emesis, after treatment with dexamethasone, metoclopramide or acepromazine were analyzed using the Wilcoxon signed-rank test. Values of p ≤ 0.05 were considered significant. 300