EFFICACY OF TOLAZOLINE AND VATINOXAN IN REDUCING ADVERSE EFFECTS OF BUTORPHANOL-AZAPERONE-MEDETOMIDINE IMMOBILIZATION IN ROCKY MOUNTAIN ELK (CERVUS CANADENSIS).

A mixture of butorphanol, azaperone, and medetomidine (BAM) is frequently used for immobilization of North American hoofstock. Common adverse effects include respiratory depression, hypoxemia, and bradycardia. In this nonblinded crossover study the efficacy of two a-2 adrenergic antagonists, tolazoline and vatinoxan, were evaluated in alleviating adverse effects of BAM in Rocky Mountain elk (Cervus canadensis). Early administration of these antagonists was hypothesized to cause an increase in heart rate, respiratory rate, partial pressure of oxygen (PaO2) and hemoglobin oxygen saturation (SpO2), as well as reduction in mean arterial blood pressure without affecting sedation levels. Eight captive adult female elk were immobilized on three separate occasions at least 14 d apart with 0.15 mg/kg butorphanol, 0.05 mg/kg azaperone, and 0.06 mg/kg medetomidine. Tolazoline (2 mg/kg IM), vatinoxan (3 mg/mg medetomidine IV) or sterile saline (2 ml IM) were administered 20 min postinduction. The BAM caused hypoxemia, bradycardia, and moderate hypertension, and because of the severe hypoxemia observed, all animals received intratracheal oxygen throughout immobilization. Heart rate, respiratory rate, rectal temperature, SpO2, PaO2, and systolic, diastolic, and mean arterial blood pressure were monitored every 5 min throughout the immobilization. Intramuscular tolazoline caused a brief but significant drop in mean arterial pressure compared with controls and a brief but nonsignificant increase in heart rate. Vatinoxan caused a significant drop in blood pressure and a brief significant increase in heart rate. Changes in respiratory rates and PaO2 were not observed with either antagonist; however, all animals received oxygen, which may have influenced this result. The depth of sedation was unchanged after administration of either drug.

Muscle tremors observed in white rhinoceroses immobilised with either etorphine-azaperone or etorphine-midazolam: An initial study.

Etorphine-azaperone is the most commonly used drug combination for chemical immobilisation of free-ranging white rhinoceroses, but causes several profound physiological disturbances, including muscle tremors. The addition of benzodiazepine sedatives, such as midazolam, has been proposed to reduce the muscular rigidity and tremors in immobilised rhinoceroses. Twenty-three free-ranging, sub-adult white rhinoceros bulls were darted and captured using a combination of etorphine plus either azaperone or midazolam. Skeletal muscle tremors were visually evaluated and scored by an experienced veterinarian, and tremor scores and distance run were compared between groups using the Wilcoxon rank sum test. No statistical differences were observed in tremor scores (p = 0.435) or distance run (p = 0.711) between the two groups, and no correlation between these variables was detected (r = -0.628; p = 0.807). Etorphine-midazolam was as effective as etorphine-azaperone at immobilising rhinoceroses, with animals running similar distances. Although the addition of midazolam to the etorphine did not reduce tremor scores compared to azaperone, it might have other beneficial immobilising effects in rhinoceroses, and further investigation is necessary to elucidate possible methods of reducing muscle tremoring during chemical immobilisation of rhinoceroses.

EVALUATION OF TWO ANESTHETIC COMBINATIONS IN LOWLAND NYALA (TRAGELAPHUS ANGASII).

Fourteen lowland nyala (Tragelaphus angasii) in managed care were successfully anesthetized for a total of 17 anesthetic events using either a combination of butorphanol (0.75 ± 0.15 mg/kg), azaperone (0.25 ± 0.05 mg/kg), and medetomidine (0.30 ± 0.06 mg/kg) (BAM) or medetomidine (0.17 ± 0.01 mg/kg), azaperone (0.22 ± 0.02 mg/kg), and alfaxalone (0.52 ± 0.08 mg/kg) (MAA) delivered intramuscularly via dart. Mean time to initial effect, sternal recumbency, lateral recumbency, handling, and intubation were recorded. The nyala were maintained in sternal recumbency with supplemental oxygenation until 60 min after initial injection. Cardiopulmonary effects were recorded every 5 min after handling until reversal. Arterial blood samples were collected every 15 min for analysis. Level of sedation and quality of recovery were scored. Anesthesia was antagonized with atipamezole (at 5 mg per mg of medetomidine) for both protocols and naltrexone (at 2 mg per mg of butorphanol) for the BAM protocol delivered intramuscularly via hand injection. Mean time to extubation, head control, and standing post reversal were recorded. No hyperthermia, acidemia, apnea, or tachycardia occurred; however, animals did display hypoxemia. Two animals in the BAM cohort required supplementation to facilitate handling. These drug combinations provided satisfactory levels of sedation in most cases for safe handling and minor procedures in lowland nyala under managed care.

Compared to etorphine-azaperone, the ketamine-butorphanol-medetomidine combination is also effective at immobilizing zebra (Equus zebra).

OBJECTIVE: To compare immobilization efficacy of a nonpotent opioid drug combination, ketamine-butorphanol-medetomidine (KBM) to the preferred etorphine-azaperone (EA) combination in zebras. STUDY DESIGN: Randomized crossover trial. ANIMALS: A group of ten adult zebra (six females and four male). METHODS: KBM and EA were administered once to the zebras in random order by dart, 3 weeks apart. Once a zebra was recumbent and instrumented, physiological parameters were measured and recorded at 5-minute intervals until 20 minutes. Antagonist drugs were administered at 25 minutes. KBM was antagonised using atipamezole (7.5 mg mg-1 medetomidine dose) and naltrexone (2 mg mg-1 butorphanol dose). EA was antagonized using naltrexone (20 mg mg-1 etorphine dose). Induction and recovery (following antagonist administration) times were recorded. Physiological parameters, including invasive blood pressure and blood gas analysis, were compared between combinations using a general linear mixed model. Data are reported as mean ± standard deviation or median (interquartile range). RESULTS: The doses of KBM and EA administered were 3.30 ± 0.18, 0.40 ± 0.02 and 0.16 ± 0.01 mg kg-1; and 0.02 ± 0.001 and 0.20 ± 0.01 mg kg-1, respectively. KBM and EA induction times were 420 (282-564) and 240 (204-294) seconds, respectively (p = 0.03). Zebras remained recumbent throughout the study procedures. Systolic blood pressure (226 ± 42 and 167 ± 42 mmHg) and oxygen partial pressure (64 ± 12 and 47 ± 13 mmHg) were higher for KBM compared to EA (p < 0.01). Recovery time, after administering antagonists, was 92 (34-1337) and 26 (22-32) seconds for KBM and EA, respectively (p = 0.03). CONCLUSIONS AND CLINICAL RELEVANCE: Compared to EA, KBM also immobilized zebras effectively. Systemic hypertension and moderate hypoxaemia are clinical concerns of KBM and severe hypoxaemia is a concern of EA. This occurrence of hypoxaemia highlights the importance of oxygen administration during immobilization.

EVALUATION OF CHEMICAL IMMOBILIZATION IN CAPTIVE BLACK BEARS ( URSUS AMERICANUS) RECEIVING A COMBINATION OF NALBUPHINE, MEDETOMIDINE, AND AZAPERONE.

To assess potential seasonal differences in responses to immobilization, we sedated eight orphaned yearling black bears ( Ursus americanus) being held for rehabilitation at a wildlife facility in Colorado, US, using a premixed combination of nalbuphine (40 mg/mL), azaperone (10 mg/mL), and medetomidine (10 mg/mL; NalMed-A) in October (autumn) prior to hibernation and again after emergence in May (spring) prior to their release. We dosed all bears at 1 mL NalMed-A per estimated 45 kg body mass (1 mL NalMed-A/45 kg), delivered by intramuscular injection using a pole syringe, to facilitate routine examination and ear tagging. Arterial blood gases were measured to assess oxygenation and acid-base status of bears both pre and post oxygen supplementation. The mean (SE) dose calculated post hoc was 0.9 (0.04) mg nalbuphine/kg, 0.2 (0.01) mg azaperone/kg, and 0.2 (0.01) mg medetomidine/kg. The mean induction time was 8 (1) min for six of the bears in October and 6 (1) min for eight bears in May. The NalMed-A combination provided good sedation in captive yearling black bears in autumn and spring and was effectively antagonized with a combination of naltrexone and atipamezole. Mild hypoxemia (PaO2: 53.5-54.4 mmHg) was the most significant side effect and was corrected (PaO2: 68.4-150.1 mmHg) with supplemental oxygen administered at 2-5 L/min for 5 min (point of sampling).

Cardiopulmonary Effects of a Partial Intravenous Anesthesia Technique for Laboratory Swine.

Various anesthetic protocols are used in laboratory swine, each with specific advantages and disadvantages. Partial intravenous anesthetic techniques (PIVA) help minimize dose-dependent cardiopulmonary effects of inhalant drugs. The aim of this study was to determine the cardiopulmonary effects of a PIVA in laboratory swine. In a prospective, nonrandomized clinical study, 8 healthy juvenile Landrace-White pigs were premedicated with azaperone (0.20 ± 0.20 mg/kg IM), dexmedetomidine (0.02 ± 0.002 mg/kg IM), and alfaxalone (2.0 ± 0.20 mg/kg IM), and anesthesia was induced with intravenous alfaxalone. Anesthesia was maintained by using constant-rate infusion of dexmedetomidine (2 µg/kg/h) and alfaxalone (25 µg/kg/min) in combination with isoflurane. After the fraction of expired isoflurane was adjusted to 1.1% to 1.5%, respiratory rate, heart rate, systemic and pulmonary arterial pressure, central venous pressure, cardiac output, bispectral index, systemic vascular resistance, and arterial and mixed venous blood gases were recorded every 10 min for 60 min. Statistical analysis consisted of repeated-measures one-way ANOVA. Significant decreases occurred in heart rate, pulmonary mean arterial pressure, pulmonary diastolic pressure, partial pressure of arterial oxygen, partial pressure of venous oxygen; significant increases occurred in respiratory rate, minute volume index, diastolic arterial blood pressure, systemic vascular resistance, and arterial pH over time. We consider that the observed statistically significant cardiopulmonary changes were clinically important and that the PIVA protocol provided hemodynamic and respiratory stability for short-term anesthesia of laboratory swine.

Tremors in white rhinoceroses (Ceratotherium simum) during etorphine-azaperone immobilisation.

Little is known about the mechanisms causing tremors during immobilisation of rhinoceros and whether cardiorespiratory supportive interventions alter their intensity. Therefore, we set out to determine the possible mechanisms that lead to muscle tremors and ascertain whether cardiorespiratory supportive interventions affect tremor intensity. We studied tremors and physiological responses during etorphine-azaperone immobilisation in eight boma-held and 14 free-living white rhinoceroses. Repeated measures analysis of variance and a Friedman test were used to determine differences in variables over time and between interventions. Spearman and Pearson correlations were used to test for associations between variables. Tremor intensity measured objectively by activity loggers correlated well (p < 0.0001; r2 = 0.9) with visual observations. Tremor intensity was greatest when animals were severely hypoxaemic and acidaemic. Tremor intensity correlated strongly and negatively with partial pressure of oxygen (PaO2 ) (p = 0.0003; r2 = 0.9995) and potential of hydrogen (pH) (p = 0.02, r2 = 0.97). It correlated strongly and positively with adrenaline concentrations (p = 0.003; r2 = 0.96), and adrenaline correlated strongly and negatively with PaO2 (p = 0.03; r2 = 0.95) and pH (p = 0.03; r2 = 0.94). Therefore, hypoxaemia and acidaemia were likely associated with the intensity of tremors through their activation of the release of tremorgenic levels of adrenaline. Tremors can be reduced if circulating adrenaline is reduced, and this can be achieved by the administration of butorphanol plus oxygen insufflation. Furthermore, to assist with reducing the risks associated with rhinoceros immobilisation, tremor intensity could be used as a clinical indicator of respiratory and metabolic compromise.

Butorphanol with oxygen insufflation improves cardiorespiratory function in field-immobilised white rhinoceros (Ceratotherium simum).

Opioid-induced immobilisation results in severe respiratory compromise in the white rhinoceros (Ceratotherium simum). The effectiveness of oxygen insufflation combined with butorphanol in alleviating respiratory depression in free-ranging chemically immobilised white rhinoceroses was investigated. In this prospective intervention study 14 free-ranging white rhinoceroses were immobilised with a combination of etorphine, azaperone and hyaluronidase. Six minutes (min) after the animals became recumbent, intravenous butorphanol was administered and oxygen insufflation was initiated. Previous boma trial results were used for comparison, using repeated measures two-way analysis of variance. The initial immobilisation-induced hypoxaemia in free-ranging rhinoceroses (arterial partial pressure of oxygen [PaO2] 35.4 mmHg ± 6.6 mmHg) was similar to that observed in boma-confined rhinoceroses (PaO2 31 mmHg ± 6 mmHg, n = 8). Although the initial hypercapnia (PaCO2 63.0 mmHg ± 7.5 mmHg) was not as severe as that in animals in the boma trial (79 mmHg ± 7 mmHg), the field-immobilised rhinoceroses were more acidaemic (pH 7.10 ± 0.14) at the beginning of the immobilisation compared with boma-immobilised rhinoceroses (pH 7.28 ± 0.04). Compared with pre-intervention values, butorphanol with oxygen insufflation improved the PaO2 (81.2 mmHg ± 23.7 mmHg, p < 0.001, 5 min vs 20 min), arterial partial pressure of carbon dioxide (55.3 mmHg ± 5.2 mmHg, p < 0.01, 5 min vs 20 min), pH (7.17 ± 0.11, p < 0.001, 5 min vs 20 min), heart rate (78 breaths/min ± 20 breaths/min, p < 0.001, 5 min vs 20 min) and mean arterial blood pressure (105 mmHg ± 14 mmHg, p < 0.01, 5 min vs 20 min). Oxygen insufflation combined with a single intravenous dose of butorphanol improved oxygenation and reduced hypercapnia and acidaemia in immobilised free-ranging white rhinoceroses.

[Perioperative intensive-medical investigations regarding compatibility of the ketamine-azaperone-general anesthesia in pigs]. / Perioperative intensivmedizinische Untersuchungen zur Verträglichkeit der Ketamin-Azaperon-AIIgemeinanästhesie beim Schwein.

was observed. Perioperatively oxygen saturation was persistently high and mean arterial pressure was steady, too. An additional Ketamine administration caused a short tachycardia during operation. After restoration of total mobility, respiratory and heart rate stayed within the reference ranges again. All EMG values in between those caused by pain stimuli were significantly below the borderline of a muscle activity in conformity with a clinically visible complete muscle relaxation. Cortisol increased simultaneously with Ketamine and Azaperone before operation, but it remained at this level until the end of the determinations, parallel to the course of Norketamine, close to the maximum before anesthesia. The complex intensive-medical monitoring confirms that under real surgical conditions the counter-regulatory effects of both drugs equalize the respective cardiovascular and respiratory side effects. It is concluded also that the increase of cortisol is likely to be more a side effect of Ketamine/Norketamine than the expression of distress by surgical interventions or by wake-up reactions, and that an intoxication by additional Ketamine dosage or motoric disorders (i.e., catalepsis) can be excluded as undesired side effects of both drugs.

Impact of general injection anaesthesia and analgesia on post-castration behaviour and teat order of piglets.

Injection anaesthesia with a combination of ketamine and azaperone (K/A) is discussed as a painless alternative to commonly used non-anaesthetized castration. To protect anaesthetized piglets from being crushed, they have to be separated from the sow for 3 h following castration. The aim of this study was to test if this separation and the different treatments would affect short-term behaviour after castration (3 to 6 h after castration) as well as weight gain. Piglets were 5 to 7 days old. Treatment Group 1 received a combination of anaesthesia and analgesia (n = 29, ketamine: 25 mg/kg BW; azaperone: 2 mg/kg BW; meloxicam: 0.4 mg/kg BW), Group 2 received only analgesia (n = 24) and Group 3 received no medication (n = 29). Behaviour and suckling order were compared for a 3 h period the day before castration and after castration. A significantly higher number of teats used by anaesthetized piglets (P = 0.004) suggests a decrease in suckling order stability. There were significant treatment effects between all three groups in the time spent at the sow's teat, with an increase in Group 2 (+69%), decrease in Group 1 (-28%), whereas the control Group 3 (+2%) almost remained unchanged. The anaesthetized piglets showed an increase in the time spent active away from the sow after castration of almost 200% (Groups 2 and 3: ∼50%, P < 0.001). However, no significant treatment effect was seen for weight gain. The results suggest that analgesia has an effect on behaviour, perhaps due to less post-castration pain. This advantage is not apparent for animals receiving additional anaesthesia, probably because of impaired coordination. Although the behavioural changes did not affect weight gain significantly, a decrease in suckling order stability indicates a certain degree of stress due to fighting over teat positions as a consequence of separation. Thus, post-castration behaviour must be taken into account when evaluating alternative castration methods.

Acid-base balance and ventilation during sternal and lateral recumbency in field immobilized black rhinoceros (Diceros bicornis) receiving oxygen insufflation: a preliminary report.

Posture, ventilation, and acid-base balance using auricular venous blood values (pH, lactate, base excess [BE], HCO(3)(-), PO(2), SO(2), and PCO(2)), oxygen saturation of hemoglobin (SpO(2)), and end-tidal carbon dioxide (P(ET)CO(2)) were compared between sternal (STE) and lateral (LAT) recumbency in free-ranging black rhinoceros (Diceros bicornis bicornis) receiving oxygen insufflation. Data are reported as median, minimum, and maximum (median [minimum, maximum]). Thirty-six desert-adapted black rhinoceros (20 male, 16 female; age 8 [1.5, 33] yr) were immobilized in Namibia in March and April of 2008, from a helicopter, by remote intramuscular injection with etorphine HCl, azaperone, and hyaluronidase. Time from darting to recumbency was 6.0 (3, 15.5) min. Data were organized into two sampling periods: sample period 1 (P1, collected within 0-20 min postdarting; 13 [6.5, 19] min) and sample period 2 (P2, collected between 20-40 min postdarting; 32 [22.3, 39] min). All animals were acidemic (pH 7.24 [7.07, 7.32]) and hypoxemic (PO(2) 51 [38, 95.2]; SO(2) 78 [64, 96] mmHg) after capture. Lactate at P1 was 7.2 (3.2, 16.8) mmol/l and decreased (P=0.01) to 4.6 (1.2, 10.9) mmol/l at P2. At P2, lactate was less (P=0.06) in LAT 3.5 (1.2, 8.6) mmol/l than in STE posture 7.4 (3.1, 10.9) mmol/l. In P2, PO(2), SO(2), and SpO(2) were higher (P=0.02, 0.10, and 0.01, respectively) in STE than in LAT. End-tidal carbon dioxide in LAT was 38 (26, 47) mmHg and increased (P<0.001) rapidly to 48 (37, 55) mmHg when animals were moved into STE; no corresponding change in PCO(2) was observed. These preliminary findings suggest that STE posture in recumbent black rhinoceros reduces dead-space ventilation and improves oxygenation. Lateral posture was associated with lower blood lactate, quicker lactate recovery, or both. It is possible that the posture of recumbent rhinoceros after capture affects lactate accumulation and clearance, or both, and procedures should consider positioning in order to enhance perfusion.

Butorphanol-azaperone-medetomidine for immobilization of captive white-tailed deer.

Drug combinations are commonly used to immobilize white-tailed deer (Odocoileus virginianus) for capture or handling. Although efficacy of various compatible and complementary drugs has been tested in clinical trials with deer, extensive negative side effects, impractical drug volume, and slow recovery from immobilization sometimes make these combinations less than ideal for routine field use. We hypothesized that a combination of butorphanol, azaperone, and medetomidine (BAM) would provide safe and effective immobilization of captive white-tailed deer while minimizing these complicating factors. We tested two dosages of this drug combination (BAM-1 and BAM-2) and two dosages of a naltrexone, tolazoline, and atipamezole antagonist combination (NTA-1 and NTA-2) with captive white-tailed deer. We characterized efficacy of drug for immobilization, quality of drug induction, and recovery after drug reversal, and we compared our findings with those of previous drug trials. Complete immobilization and excellent induction quality was achieved with a low volume dosage of BAM-2. Time to drug induction and deer recumbency for BAM-2 compared favorably with results from previous trials involving xylaxine/ ketamine and medetomidine/ketamine but without risk of hyperthermia. We found no differences in time to deer recovery for NTA-1 and NTA-2, with deer treated with either combination standing by 30 min postinjection. Regardless of immobilizing drugs used, we suggest practitioners monitor for signs of circulatory deficiency in deer and provide supplemental oxygen when needed.

Severe hypoxaemia in field-anaesthetised white rhinoceros (Ceratotherium simum) and effects of using tracheal insufflation of oxygen.

White rhinoceros anaesthetised with etorphine and azaperone combination develop adverse physiological changes including hypoxia, hypercapnia, acidosis, tachycardia and hypertension. These changes are more marked in field-anaesthetised rhinoceros. This study was designed to develop a technique to improve safety for field-anaesthetised white rhinoceros by tracheal intubation and oxygen insufflation. Twenty-five free-ranging white rhinoceros were anaesthetised with an etorphine and azaperone combination for translocation or placing microchips in their horns. Once anaesthetised the rhinoceros were monitored prior to crating for transportation or during microchip placement. Physiological measurements included heart and respiratory rate, blood pressure and arterial blood gas samples. Eighteen rhinoceros were intubated using an equine nasogastric tube passed nasally into the trachea and monitored before and after tracheal insufflation with oxygen. Seven rhinoceros were not intubated or insufflated with oxygen and served as controls. All anaesthetised rhinoceros were initially hypoxaemic (percentage arterial haemoglobin oxygen saturation (%O2Sa) = 49% +/- 16 (mean +/- SD) and PaO2 = 4.666 +/- 1.200 kPa (35 +/- 9 mm Hg)), hypercapnic (PaCO2 = 8.265 +/- 1.600 kPa (62 +/- 12 mm Hg)) and acidaemic (pHa = 7.171 +/- 0.073 ). Base excess was -6.7 +/- 3.9 mmol/l, indicating a mild to moderate metabolic acidosis. The rhinoceros were also hypertensive (systolic blood pressure = 21.861 +/- 5.465 kPa (164 +/- 41 mm Hg)) and tachycardic (HR = 107 +/- 31/min). Following nasal tracheal intubation and insufflation, the %O2Sa and PaO2 increased while blood pHa and PaCO2 remained unchanged. Tracheal intubation via the nose is not difficult, and when oxygen is insufflated, the PaO2 and the %O2Sa increases, markedly improving the safety of anaesthesia, but this technique does not correct the hypercapnoea or acidosis. After regaining their feet following reversal of the anaesthesia, the animals' blood gas values return towards normality.

Comparative study of the sedative and antinociceptive effects of levomepromazine, azaperone and midazolam in laboratory animals

Os efeitos sedativos e antinociceptivos da levomepromazina, azaperone e midazolam foram avaliados utilizando-se três testes de comportamento em ratos e camundongos. No teste da atividade locomotora espontânea em campo aberto observou-se que tanto o comportamento exploratório como a atividade locomotora espontânea foram significativamente diminuídos quando se utilizou levomepromazina e azaperone. O efeito causado pelo azaperone foi menos prolongado quando comparado ao da levomepromazina. O midazolam causou diminuição do comportamento exploratório sem alterar a atividade locomotora espontânea. Quando se avaliou o efeito antinociceptivo por meio da latência para o reflexo da retirada da cauda em ratos após estímulo doloroso, as drogas não apresentaram nenhum efeito antinociceptivo observável. No teste das contorções em camundongos, os fármacos foram capazes de abolir as contorções quando comparados ao efeito do grupo-controle. Levomepromazina, azaperone e midazolam nas doses utilizadas foram capazes de inibir o comportamento exploratório de ratos, comprovando seus efeitos sedativos. Com relação aos efeitos antinociceptivos para dor visceral, eles foram capazes de inibir as contorções.

Chemical anesthesia of northern sea otters (Enhydra lutris): results of past field studies.

Between 1987 and 1997, we chemically immobilized 597 wild sea otters (Enhydra lutris) in Alaska for the collection of biological samples or for surgical instrumentation. One drug-related sea otter fatality occurred during this time. Fentanyl in combination with diazepam produced consistent, smooth inductions with minimal need for supplemental anesthetics during procedures lasting 30-40 min. Antagonism with naltrexone or naloxone was rapid and complete, although we observed narcotic recycling in sea otters treated with naloxone. For surgical procedures, we recommend a fentanyl target dose of 0.33 mg/kg of body mass and diazepam at 0.11 mg/kg. For nonsurgical biological sample collection procedures, we recommend fentanyl at 0.22 mg/kg and diazepam at 0.07 mg/kg. We advise the use of the opioid antagonist naltrexone at a ratio of 2:1 to the total fentanyl administered during processing.

Paradoxical excitement following the intravenous administration of azaperone in the horse.

The rapid intravenous administration of the butyrophenone tranquilliser, azaperone, at a dose rate of 0.29-0.57 mg/kg body weight resulted in the immediate onset of excitement and ataxia of varying degree in over half the animals. The severity of the reaction appeared to be related to the size of the animal. Other side effects such as salivation, sweating, muscle tremor and vocalisation were also observed. The possible causes of this paradoxical reaction to the tranquilliser are discussed.