Sedative and antinociceptive effects of dexmedetomidine and buprenorphine after oral transmucosal or intramuscular administration in cats

The Effect of a Subsequent Dose of Dexmedetomidine or Other Sedatives following an Initial Dose of Dexmedetomidine on Electrolytes, Acid-Base Balance, Creatinine, Glucose, and Cardiac Troponin I in Cats: Part II

The administered dose of dexmedetomidine may occasionally fail to produce the anticipated sedative effects. Therefore, a subsequent dose or administration of another sedative may enhance sedation; however, patient safety may be affected. The safety of seven different drugs administered at the following time point after an insufficient dose of dexmedetomidine was evaluated in a crossover, blind, experimental study that included six healthy adult cats. All cats received an initial dose of dexmedetomidine and a subsequent dose of either dexmedetomidine (Group DD), NS 0.9% (DC), tramadol (DT), butorphanol (DBT), buprenorphine (DBP), ketamine (DK), or midazolam (DM). Animal safety was assessed using repeated blood gas analysis and measurement of electrolytes, glucose, cardiac troponin I, and creatinine to evaluate cardiac, respiratory, and renal function. The median values of creatinine, cardiac troponin I, pH, partial pressure of carbon dioxide, potassium, and sodium did not change significantly throughout the study. Heart rate was significantly decreased in all groups after administration of the drug combinations, except for in the DK group. Respiratory rate decreased significantly after administration of the initial dose of dexmedetomidine and in the DBP and DM groups. The partial pressure of oxygen, although normal, decreased significantly after the administration of dexmedetomidine, whereas the median concentration of glucose increased significantly following the administration of dexmedetomidine. The results of our study suggest that the drug combinations used did not alter the blood parameters above normal limits, while cardiac and renal function were not compromised. Therefore, a safe level of sedation was achieved. However, the administration of dexmedetomidine reduced the partial pressure of oxygen; thus, oxygen supplementation during sedation may be advantageous. Additionally, the increase in glucose concentration indicates that dexmedetomidine should not be used in cats with hyperglycaemia, whereas the decrease in haematocrit suggests that dexmedetomidine is not recommended in anaemic cats.

A Comparison of the Intrarectal and Intramuscular Effects of a Dexmedetomidine, Ketamine and Midazolam Mixture on Tear Production in Cats: A Randomized Controlled Trial

Cats are often easily stressed and uncooperative. The use of sedative agents in the feline species is widely used to perform even minor clinical and diagnostic procedures. The aim of this study is to assess the impact on tear film production of the intrarectal route (IR) administration of a mixture of dexmedetomidine, ketamine and midazolam in comparison with the intramuscular (IM) one. A group of twenty cats were involved in a randomized and blinded clinical trial. A clinical and ophthalmological examination was conducted on the cats. The IR group received dexmedetomidine 0.003 mg kg-1, ketamine 4 mg kg-1 and midazolam 0.4 mg kg-1; the IM group received dexmedetomidine 0.003 mg kg-1, ketamine 2 mg kg-1 and midazolam 0.2 mg kg-1. A Shirmer tear test I (STT- I) was conducted 1 h before sedation and 2', 10', 20', 30', 40', and 80' post drug administration. The reaction to STT-I administration was also evaluated. The IM group has a lower mean tear production than the IR group for all time points evaluated. Cats in the IM group showed less reaction to STT-I administration. This study may suggest that the effect of sedative agents administered by the IR route has a lower incidence on tear production than the IM one. The use of eye lubricant is recommended in any case.

Multiple uses of dexmedetomidine in small animals: a mini review

Dexmedetomidine is an alpha-2 adrenergic agonist, which use had an exponential increase in human and veterinary medicine in the last 10 years. The aim of this mini review is to summarize the various uses of dexmedetomidine underlining its new applications and capabilities in the small animals' clinical activity. While this drug was born as sedative in veterinary medicine, some studies demonstrated to be effective as an analgesic both in single administration and in continuous infusion. Recent studies have also shown the role of dexmedetomidine as an adjuvant during locoregional anesthesia, increasing the duration of the sensitive block and consequently decreasing the demand for systemic analgesics. The various analgesic properties make dexmedetomidine an interesting drug for opioid-free analgesia. Some studies highlighted a potential neuroprotective, cardioprotective and vasculoprotective role of dexmedetomidine, thus conferring it a place in critical care medicine, such as trauma and septic patients. Dexmedetomidine has demonstrated to be a multitasking molecule and it is ready to face new challenges.

Euthanasia of dogs and cats by veterinarians in New Zealand: protocols, procedures and experiences

AIMS

To collect data on protocols used by New Zealand veterinarians to perform euthanasia of dogs and cats, and to explore opinions towards the training they received in euthanasia during veterinary school.

METHODS

A cross-sectional survey was administered to all veterinarians registered with the Veterinary Council of New Zealand. The survey asked respondents about their practices' policies for euthanasia; protocols for performing euthanasia of dogs and cats; opinions towards euthanasia training received in veterinary school; and subsequent experiences with euthanasia in practice. Descriptive statistics were provided for all quantitative study variables and thematic analysis was performed on the free-text comments.

RESULTS

The survey was completed by 361/1,448 (24.9%) veterinarians in companion or mixed animal practice. The mean number of dogs and cats euthanised each month were 7.2 (median 5; min 0; max 60) and 7.9 (median 5; min 0; max 60), respectively. Fewer than half of respondents reported that their clinic had a standard protocol for euthanising dogs (147/361; 40.7%) and cats (157/361; 43.5%). For euthanasia of dogs, 119/361 (32.9%) always used sedation while 71/361 (19.7%) indicated that they would not use sedation. For euthanasia of cats, 170/361 (47.1%) always used sedation while 53/361 (14.7%) indicated that they would not use sedation. Placement of IV catheters, methods for patient restraint, preferences towards the presence of owners during euthanasia, services provided with euthanasia, and discussions with owners were also highly variable and handled case-by-case depending on the client, patient, and clinical scenario. When asked about the euthanasia training received at veterinary school, it was generally ranked as below satisfactory, with approximately one third of respondents indicating that they received no training in dealing with emotional clients (113/361; 31.3%), sedation protocols for euthanasia (107/361; 29.6%), or managing compassion fatigue (132/361; 36.6%). Most respondents (268/361; 74.2%) received no formal training in euthanasia after graduation and learned from experience or discussions with colleagues. Providing animals and owners with a good experience during the euthanasia process was highlighted as important for managing compassion fatigue.

CONCLUSIONS

Euthanasia is a common procedure in companion animal practice and there is considerable variation in how veterinarians approach both the technical and non-technical elements. Training provided during veterinary school was generally considered below satisfactory, particularly regarding managing compassion fatigue and clients' emotional needs.

CLINICAL RELEVANCE

Providing veterinarians with additional training on adapting their euthanasia protocols to different clinical scenarios may improve the experience for patients, owners and veterinary staff.

Comparison of Certain Intrarectal versus Intramuscular Pharmacodynamic Effects of Ketamine, Dexmedetomidine and Midazolam in Cats

The aim of this clinical trial was to evaluate the impacts of administration via the intrarectal route (IR) in cats on their heart and respiratory rates, blood pressure, body temperature, and sedation quality compared to the intramuscular route (IM). The intramuscular group (IMG) received 0.003 mg kg−1 dexmedetomidine, 2 mg kg−1 ketamine, and 0.2 mg kg−1 midazolam while the intrarectal group (IRG) protocol was 0.003 mg kg−1 dexmedetomidine, 4 mg kg−1 ketamine, and 0.4 mg kg−1 midazolam. Cardiorespiratory values, temperature, and sedation score were measured 2 min after administration and then every 5 min up to the 40th minute. Cats belonging to IRG reacted less strongly to the drug, as opposed to those receiving intramuscular administration (2/10 in IRG vs. 8/10 in IMG). Average time between drug administration and standing position was 44.9 ± 5.79 in IRG and 57 ± 9.88 min in IMG. In IRG, maintenance of SpO₂ values is >95% at each time point. Median and range peak of sedation {7 (5)} in IMG occurs at 20th, 25th, and 30th minutes post drug administration while was lower in IRG. Cardiorespiratory values were slightly lower in IMG than in IRG, but always constant in both treatments. Temperature did not differ between groups. At this dosage, although sedation score was higher in IMG, intrarectal route could be efficacious for performing minimally invasive clinical and diagnostic procedures in cats.

The impact of a stress-reducing protocol on the quality of pre-anaesthesia in cats

INTRODUCTION

Transport to the clinic is a major source of stress for cats. The process involves being put into a carrier, driven in a car and handled. Cats are therefore removed from the safe-haven of their territory and experience many stressful stimuli and interactions.

METHODS

In the present study, 31 cats were transported to the clinic following a low-stress transport protocol and compared with a control group of 36 cats whose owners did not follow the protocol. This protocol involved preparing a cat carrier basket with F3 pheromone and keeping it covered and stable during the car journey from the home to the clinic. Pre-anaesthesia information was recorded for cardiac rate, respiratory rate, tolerance to handling, time for sedation to be achieved and dose of propofol required for induction and endotracheal intubation.

RESULTS

The group exposed to the low-stress transport protocol took less time to reach sedation and needed a lower dose of propofol for induction than the control group.

CONCLUSION

These results suggest that, in cats, pre-anaesthetic and induction requirements are influenced by lower-stress transport and handling.

Pharmacokinetics, sedation and hemodynamic changes following the administration of oral transmucosal detomidine gel in cats

OBJECTIVES

The aim of this study was to describe the pharmacokinetics of oral transmucosal (OTM) detomidine gel in healthy cats and assess its effects on sedation and hemodynamic variables.

METHODS

Eight adult cats weighing 4.12 kg ± 0.72 received 4 mg/m2 detomidine gel onto the buccal mucosa. Level of sedation, heart rate (HR), blood pressure (BP) and respiratory rate (f R) were assessed at predetermined intervals following administration. Blood samples for plasma detomidine concentrations and venous blood gas variables were collected from a medial saphenous catheter. Plasma detomidine concentrations were analyzed using ultra-high-pressure liquid chromatography with mass spectrometry detection, and pharmacokinetic estimates were obtained with compartmental methods. Data were analyzed using ANOVA and paired t-test or appropriate non-parametric tests.

RESULTS

Sedation occurred in all cats, and was increased from baseline at 30 mins (P <0.001). Decreases in HR occurred from 15-60 mins, ranging from 140 to 165 beats per min (P <0.001). Blood glucose increased from 101 ± 12 mg/dl to 168 ± 27.3 mg/dl at 60 mins (P = 0.004). Systolic blood pressure decreased from baseline (139 ± 14.8 mmHg) to 103 ± 23.0 mmHg at 60 mins (P = 0.023). All changes abated by 120 mins. Emesis occurred in 7/7 cats within 2 mins of gel administration. Geometric mean (coefficient of variation) for clearance was 220.7 ml/min/kg (35.3 ml/min/kg), volume of distribution was 14.9 l/kg (39.9 l/kg) (both a function of bioavailability) and elimination half-life was 46.9 mins (16.0 mins). Maximum plasma concentrations of 10.5 ng/ml (35.5 ng/ml) detomidine occurred at 36.9 mins (21.5 mins).

CONCLUSIONS AND RELEVANCE

OTM detomidine gel produced moderate sedation with minimal undesirable side effects in healthy cats, although emesis occurred in all cats. The pharmacokinetic profile supports short-term, minimally invasive sedation in this species. Further studies are warranted to assess its safety and feasibility for use in debilitated cats, or prior to general anesthesia.

2020 AAHA Anesthesia and Monitoring Guidelines for Dogs and Cats

Risk for complications and even death is inherent to anesthesia. However, the use of guidelines, checklists, and training can decrease the risk of anesthesia-related adverse events. These tools should be used not only during the time the patient is unconscious but also before and after this phase. The framework for safe anesthesia delivered as a continuum of care from home to hospital and back to home is presented in these guidelines. The critical importance of client communication and staff training have been highlighted. The role of perioperative analgesia, anxiolytics, and proper handling of fractious/fearful/aggressive patients as components of anesthetic safety are stressed. Anesthesia equipment selection and care is detailed. The objective of these guidelines is to make the anesthesia period as safe as possible for dogs and cats while providing a practical framework for delivering anesthesia care. To meet this goal, tables, algorithms, figures, and "tip" boxes with critical information are included in the manuscript and an in-depth online resource center is available at aaha.org/anesthesia.

Oral Transmucosal or Intramuscular Administration of Dexmedetomidine-Methadone Combination in Dogs: Sedative and Physiological Effects

Simple Summary

During the last decade, new alternative non-invasive administration routes for drug delivery have gained interest in veterinary medicine. The administration of drugs via the oral transmucosal route is non-invasive, painless, easy to perform, and generally well tolerated. Furthermore, it avoids gastric acid degradation typical of oral administration. All these characteristics contribute to make this administration route very attractive, especially for veterinary patients who are difficult to inject, fearful, or anxious. In contrast, intramuscular injection is associated with pain and requires more invasive restraint, potentially incrementing patients’ discomfort. The aim of this study was to assess and compare the sedative and clinical effects of a dexmedetomidine–methadone combination following either oral transmucosal and intramuscular administration in healthy dogs and to record any possible adverse effects following each administration route. The present study suggests that oral transmucosal administration of dexmedetomidine and methadone combination provided a satisfactory level of sedation, allowing safe handling of the patients with less pronounced cardiorespiratory effects. Indeed, thanks to the lesser impact on the cardiac function, it could be considered as a useful option for those patients difficult to restrain in which cardiovascular stability should be preserved.

Abstract

The aim of this study was to compare the sedative and physiological effects following either oral transmucosal (OTM) or intramuscular administration of dexmedetomidine–methadone combination in healthy dogs. Thirty dogs were randomly assigned to receive a dexmedetomidine–methadone combination either by the OTM (n = 15) or intramuscular (n = 15) route. Sedation was scored 10, 20, and 30 min after drugs administration. Heart rate (HR), non-invasive blood pressure (NIBP), respiratory rate (f_R), and body rectal temperature were recorded before drugs administration and then every 10 min for 30 min. Propofol dose required for orotracheal intubation was recorded. Sedation scores increased over time within both groups with higher values in intramuscular group (p < 0.05). Within each group, HR decreased significantly compared with baseline (p < 0.001) and was significantly lower in intramuscular group compared with the OTM group (p < 0.001). In both groups, NIBP increased significantly compared with baseline (p < 0.05). In the intramuscular group, f_R was lower compared with the OTM group at all the observational time points (p < 0.001). Propofol dose was lower in the intramuscular group (p < 0.05). Compared to intramuscular dexmedetomidine–methadone, OTM combination produced lower but effective sedation in healthy dogs.

Feline procedural sedation and analgesia: When, why and how

PRACTICAL RELEVANCE

Procedural sedation and analgesia (PSA) describes the process of depressing a patient's conscious state to perform unpleasant, minimally invasive procedures, and is part of the daily routine in feline medicine. Maintaining cardiopulmonary stability is critical while peforming PSA.

CLINICAL CHALLENGES

Decision-making with respect to drug choice and dosage regimen, taking into consideration the cat's health status, behavior, any concomitant diseases and the need for analgesia, represents an everyday challenge in feline practice. While PSA is commonly perceived to be an uneventful procedure, complications may arise, especially when cats that were meant to be sedated are actually anesthetized.

AIMS

This clinical article reviews key aspects of PSA in cats while exploring the literature and discussing complications and risk factors. Recommendations are given for patient assessment and preparation, clinical monitoring and fasting protocols, and there is discussion of how PSA protocols may change blood results and diagnostic tests. An overview of, and rationale for, building a PSA protocol, and the advantages and disadvantages of different classes of sedatives and anesthetics, is presented in a clinical context. Finally, injectable drug protocols are reported, supported by an evidence-based approach and clinical experience.

Efeitos cardiovasculares da medetomidina e cetamina em Puma concolor e tempo de recuperação após aplicação de ioimbina ou atipamezole

RESUMO O objetivo deste estudo foi avaliar as alterações cardiorrespiratórias causadas pela medetomidina associada à cetamina, e o tempo de recuperação após aplicação intramuscular de atipamezole ou ioimbina em Puma concolor. Para isso, foi realizada a aplicação de medetomidina (100µg/kg) associada à cetamina (5mg/kg) em 11 onças-pardas, sendo os parâmetros cardiorrespiratórios registrados a cada 15 minutos, durante 90 minutos de avaliação. Em seguida, a anestesia foi revertida com aplicação intramuscular de ioimbina (0,4mg/kg; n=5) ou atipamezole (0,25mg/kg; n=6), sendo analisado o tempo até a recuperação. Dos parâmetros cardiorrespiratórios avaliados, houve diferença apenas na frequência respiratória (entre os momentos 60 e 90 minutos), estando esta, todavia, dentro do intervalo de referência para a espécie. Além disso, verificou-se tempo para decúbito esternal significativamente menor nos animais do grupo atipamezole (18±7 minutos), quando comparado ao grupo ioimbina (36±17 minutos), entretanto o tempo de recuperação completa foi estatisticamente igual entre os dois reversores analisados. Assim, a associação anestésica promoveu anestesia eficiente, segura e de rápida indução em onças-pardas, permitindo a imobilização dos animais durante os 90 minutos de avaliação, sem a ocorrência de complicações. Ao se comparar a reversão anestésica com atipamezole e ioimbina, observou-se equivalência dos fármacos no tempo de recuperação completa dos animais.

Use of nociceptive threshold testing in cats in experimental and clinical settings: a qualitative review

OBJECTIVE

The objective of this study was to review the scientific articles on the use of nociceptive threshold testing (NTT) in cats and to summarize the clinical and experimental applications in this species.

DATABASES USED

Pertinent literature was searched with PubMed, Scopus, Web of Science, Universitätsbibliothek Basel (swissbib Basel Bern) and Google Scholar. The search was then refined manually based first on article titles and abstracts, and subsequently on full texts.

CONCLUSIONS

Of the four classical acute nociceptive models used for NTT, thermal and mechanical are most commonly used in cats. Thermal stimulation is applicable in experimental settings and has been used in pharmacodynamics studies assessing feline antinociception. Although mechanical stimulation is currently less used in cats, in the future it might play a role in the evaluation of clinical feline pain. However, the low response reliability after stimulus repetition within a narrow time interval represents a major limitation for the clinical use of mechanical thresholds in this species. Challenges remain when thermal thresholds are used to investigate analgesics that have the potential to affect skin temperature, such as opioids and α2-adrenergic agonists, and when a model of inflammatory pain is reproduced in experimental cats with the purpose of evaluating non-steroidal anti-inflammatory drugs as analgesics.

Pharmacologic Methods: An Update on Optimal Presedation and Euthanasia Solution Administration

Pre-euthanasia sedation or anesthesia offers many benefits. It allows the owners to spend time with their pet before euthanasia, improves safety for the person performing euthanasia and others who are present, decreases stress for the patient, reduces or eliminates the need for physical restraint for intravenous injection. Under anesthesia, non-intravenous routes may be used for administration of euthanasia solutions. Some drugs that do not require injection; the oral transmucosal route is noninvasive and suitable for several drugs or drug combinations. The oral route also is feasible, but there are fewer data available on suitable drugs and doses.

Pharmacokinetics and pharmacodynamic effects of oral transmucosal and intravenous administration of dexmedetomidine in dogs

OBJECTIVE

To determine pharmacokinetic and pharmacodynamic properties of the injectable formulation of dexmedetomidine administered via the oral transmucosal (OTM) route to healthy dogs.

ANIMALS

6 healthy dogs.

PROCEDURES

Injectable dexmedetomidine was administered IV (5 μg/kg) or via the OTM route (20 μg/kg) in a blinded, single-observer, randomized crossover study. Dogs received dexmedetomidine and a sham treatment at each administration. Serial blood samples were collected from a catheter in a saphenous vein. Heart rate, respiratory rate, and subjective sedation score were assessed for 24 hours after administration. Plasma samples were analyzed for dexmedetomidine concentrations by use of ultraperformance liquid chromatography-tandem mass spectrometry.

RESULTS

For the OTM route, the mean ± SD maximum plasma concentration was 3.8 ± 1.3 ng/mL, which was detected 73 ± 33 minutes after administration. The mean maximum concentration for the IV dose, when extrapolated to the time of administration, was 18.6 ± 3.3 ng/mL. The mean terminal-phase half-life was 152 ± 146 minutes and 36 ± 6 minutes for OTM and IV administration, respectively. After IV administration, total clearance was 8.0 ± 1.6 mL/min/kg and volume of distribution at steady state was 371 ± 72 mL/kg. Bioavailability for OTM administration of dexmedetomidine was 11.2 ± 4.5%. Peak sedation scores did not differ significantly between routes of administration. Decreases in heart rate, respiratory rate, and peak sedation score were evident sooner after IV administration.

CONCLUSIONS AND CLINICAL RELEVANCE

OTM administration of the injectable formulation of dexmedetomidine resulted in a similar degree of sedation and prolonged duration of action, compared with results for IV administration, despite relatively low bioavailability.

Combined spinal and general anaesthesia in 58 cats undergoing various surgical procedures: description of technique and retrospective perioperative evaluation

OBJECTIVES

The aim of this retrospective study was to describe the spinal anaesthesia (SA) technique and evaluate the incidence of perioperative complications in cats.

METHODS

The anaesthetic records of cats of American Society of Anaesthesiologists physical status I, II and III, which received general and SA for different surgeries between 2012 and 2016, were examined. SA was administered through a 25 G Quincke needle, using an isobaric solution of bupivacaine and morphine at the level of either the L7-S1 interspaces (sternal recumbency) or the L5-6/L6-7 interspaces (lateral recumbency). Procedural failure rate (PFR), drugs and dose used, heart rate (HR), arterial blood pressure, incidence of bradycardia (HR <100 bpm) and hypotension (mean arterial pressure [MAP] <60 mmHg for at least 5 mins), intraoperative rescue analgesia (iRA) and any other detrimental events and their treatment until discharge were recorded. Abdominal surgery cases were excluded from the intraoperative evaluation.

RESULTS

A total of 58 anaesthetic records met the inclusion criteria and were analysed. PFR related to the space of injection (L7-S1 vs L5-6/L6-7) was 3/11 (27%) and 1/47 (2%), respectively (P = 0.017). The total median dose of intrathecal bupivacaine and morphine was 0.8 (range 0.5-1.6 mg/kg) and 0.10 (0.05-0.18 mg/kg), respectively. Nine of 46 (20%) cats received iRA, and no iRA cases were reported with a dose of bupivacaine higher than 0.8 mg/kg. Median HR and MAP before intrathecal injection (T0) and 10 mins after (T1) were, respectively, 118 bpm (range 74-190 bpm) and 106 bpm (67-160 bpm) (P = 0.005), and 65 mmHg (range 50-94 mmHg) and 52 mmHg (range 35-85 mmHg) (P = 0.003). Bradycardia was reported in 18/46 (39%) cats and hypotension in 23/46 (50%) cats. No complications were recorded during the observation period.

CONCLUSIONS AND RELEVANCE

SA was characterised by a low PFR when performed at the L5-6/L6-7 interspaces and low postoperative complications. Hypotension and bradycardia were the most common side effects.

State of the art analgesia-Recent developments pharmacological approaches to acute pain management in dogs and cats: Part 2

There has been considerable interest in the area of acute pain management over recent years, focusing on pain assessment, pharmacological and non-pharmacological interventions. The evidence base for our clinical decision making and treatment of patients is ever increasing and becoming more robust. There is still a tendency to base some aspects of pain management on poor quality evidence and this requires further input in years to come. With new literature come new ideas and this review will detail the current knowledge base behind pharmacological management of acute pain in dogs and cats. The known mechanisms of action of each analgesic and its evidence will be considered. The second part of this review will consider the non-traditional analgesics, describing their component drugs individually, thereby focusing on their mechanisms of action and the current evidence for their use in acute pain management.

Comparison of intramuscular butorphanol and buprenorphine combined with dexmedetomidine for sedation in cats

Objectives The objective of this study was to compare the sedative effect of butorphanol-dexmedetomidine with buprenorphine-dexmedetomidine following intramuscular (IM) administration in cats. Methods Using a prospective, randomised, blinded design, 40 client-owned adult cats were assigned to receive IM dexmedetomidine (10 µg/kg) combined with either butorphanol (0.4 mg/kg) ('BUT' group) or buprenorphine (20 µg/kg) ('BUP' group). Sedation was scored using a previously published multidimensional composite scale before administration (T0) and 5, 10, 15 and 20 mins afterwards (T5, T10, T15 and T20, respectively). Alfaxalone (1.5 mg/kg) was administered IM at T20 if the cat was not deemed adequately sedated to place an intravenous catheter. Adverse events were recorded. Friedman two-way ANOVA analysed sedation scores within groups. Mann-Whitney Rank Sum test compared sedation scores between groups; Fisher's exact test analysed the frequency of alfaxalone administration and adverse events. P <0.05 was considered statistically significant. Results Sedation scores between groups were similar at baseline, but at T5, T10, T15 and T20 scores were higher in the BUT group ( P <0.01). Within both groups, sedation scores changed over time and the highest sedation scores were reached at T10. Requirement for additional sedation was similar between groups: two cats in the BUT group and five cats in the BUP group. One cat and 11 cats vomited ( P = 0.002) in the BUT and BUP groups, respectively. No other adverse events were recorded. Conclusions and relevance At these doses, IM buprenorphine-dexmedetomidine provides inferior sedation and a higher incidence of vomiting than butorphanol-dexmedetomidine in cats. Butorphanol-dexmedetomidine may be preferred for feline sedation, especially where vomiting is contraindicated.

Pharmacokinetic comparison of two buprenorphine formulations after buccal administration in healthy male cats

Objectives The objective of this study was to compare the pharmacokinetics of compounded and commercially available aqueous formulations of buprenorphine after a single buccal dose to healthy cats and to evaluate the concentrations of a compounded buprenorphine solution over 21 days when stored at room temperature (RT; 22-24°C) with exposure to light or when refrigerated at 4°C while protected from light. Methods Six young healthy male cats were administered single buccal doses of compounded and commercially available formulations of buprenorphine (0.03 mg/kg) using a randomized, blinded, two-period crossover design. Blood samples were obtained over a 24 h period and plasma buprenorphine concentrations were determined using ultra-high-pressure liquid chromatography with mass spectrometry detection. Three batches of the compounded formulation were stored at RT or 4°C and aliquots were evaluated over 21 days for buprenorphine concentration using high-performance liquid chromatography with fluorescence detection. Results Plasma concentrations of buprenorphine were above the limit of quantification up to 6 h in some cats and up to 3 h in all cats. The area under the curve was significantly less for the compounded formulation ( P = 0.004). A significant difference was not detected between formulations for time to maximum concentration ( P = 0.11), maximum concentration ( P = 0.06), half-life ( P = 0.88) and mean residence time ( P = 0.57). Buprenorphine concentration in the compounded formulation was not affected by storage condition or time and remained between 90% and 110% of the target concentration at all time points. Conclusions and relevance A buprenorphine solution prepared from sublingual tablets is absorbed after buccal administration in healthy cats. The extent of absorption is significantly less than that of the commercially available formulation. The compounded solution maintains an acceptable buprenorphine concentration for at least 21 days when stored at RT or refrigerated.

Sedative and physiological effects of brimonidine tartrate ophthalmic solution in healthy cats

OBJECTIVE

To determine the effects of brimonidine tartrate ophthalmic solution on sedation, heart rate (HR), respiratory frequency (f_R), rectal temperature (RT) and noninvasive mean arterial pressure (MAP) in healthy cats.

STUDY DESIGN

Randomized, blinded crossover study, with 1 week washout between treatments.

ANIMALS

Six healthy purpose-bred cats.

METHODS

Brimonidine tartrate ophthalmic solution 0.1% (one or two drops; 58.6 ± 3.3 μg per drop) or a control solution (artificial tear solution) was administered to six healthy cats. Behavioural observations and measurements of HR, f_R, RT and MAP were recorded before and at 30, 60, 90, 120, 180, 240, 300 and 360 minutes after topical administration. Behavioural scores were analysed using Friedman's test for repeated measures to evaluate the time effect in each treatment and treatment effect at each time point. Physiological variables (HR, f_R, RT and MAP) were analysed using two-way analysis of variance for repeated measures to evaluate the time and treatment effects. The level of significance was set at p < 0.05.

RESULTS

Dose-dependent behavioural and physiological responses were noted. A dose of two drops of brimonidine resulted in sedation in the cats and decreased HR and MAP. Significant sedative effects occurred between 30 and 120 minutes and for physiological responses up to 360 minutes. The most frequent adverse reaction was vomiting, occurring within 40 minutes in all six cats administered two drops and five of the six cats administered one drop of brimonidine.

CONCLUSIONS AND CLINICAL RELEVANCE

The results demonstrated that ocular administration of brimonidine 0.1% ophthalmic solution induced sedation in cats and some cardiovascular effects usually associated with α₂-adrenoceptor agonists. Further studies should be performed to determine clinical applications for this agent in cats.

Pharmacokinetics of oral transmucosal and intramuscular dexmedetomidine combined with buprenorphine in cats

Plasma concentrations and pharmacokinetics of dexmedetomidine and buprenorphine after oral transmucosal (OTM) and intramuscular (i.m.) administration of their combination in healthy adult cats were compared. According to a crossover protocol (1-month washout), a combination of dexmedetomidine (40 μg/kg) and buprenorphine (20 μg/kg) was given OTM (buccal cavity) or i.m. (quadriceps muscle) in six female neutered cats. Plasma samples were collected through a jugular catheter during a 24-h period. Plasma dexmedetomidine and buprenorphine concentrations were determined by liquid chromatography-tandem mass spectrometry. Plasma concentration-time data were fitted to compartmental models. For dexmedetomidine and buprenorphine, the area under the plasma concentration-time curve (AUC) and the maximum plasma concentrations (Cmax ) were significantly lower following OTM than following i.m. administration. For buprenorphine, time to reach Cmax was also significantly longer after OTM administration than after i.m. injection. Data suggested that dexmedetomidine (40 μg/kg) combined with buprenorphine (20 μg/kg) is not as well absorbed from the buccal mucosa site as from the intramuscular injection site.

Antinociceptive effects of three escalating dexmedetomidine and lignocaine constant rate infusions in conscious horses

Dexmedetomidine and lignocaine IV are used clinically to provide analgesia in horses. The aims of this study were to investigate the antinociceptive effects, plasma concentrations and sedative effects of 2, 4 and 6 µg/kg/h dexmedetomidine IV, with a bolus of 0.96 µg/kg preceding each continuous rate infusion (CRI), and 20, 40 and 60 µg/kg/min lignocaine IV, with a bolus of 550 µg/kg preceding each CRI, in 10 Swiss Warmblood horses. Electrically elicited nociceptive withdrawal reflexes were evaluated by deltoid muscle electromyography. Nociceptive threshold and tolerance were determined by electromyography and behaviour following single and repeated stimulation. Plasma concentrations of drugs were determined by liquid chromatography and mass spectrometry. Sedation was scored on a visual analogue scale. Dexmedetomidine increased nociceptive threshold to single and repeated stimulation for all CRIs, except at 2 µg/kg/h, where no increase in single stimulation nociceptive threshold was observed. Dexmedetomidine increased nociceptive tolerance to single and repeated stimulation at all CRIs. There was large individual variability in dexmedetomidine plasma concentrations and levels of sedation; the median plasma concentration providing antinociceptive effects to all recorded parameters was 0.15 ng/mL, with a range from <0.02 ng/mL (below the lower limit of quantification) to 0.25 ng/mL. Lignocaine increased nociceptive threshold and tolerance to single and repeated stimulation at CRIs of 40 and 60 µg/kg/min, corresponding to plasma lignocaine concentrations >600 ng/mL. Only nociceptive tolerance to repeated stimulation increased at 20 µg/kg/min lignocaine. Lignocaine at 40 µg/kg/min and dexmedetomidine at 4 µg/kg/h were the lowest CRIs resulting in consistent antinociception. Lignocaine did not induce significant sedation.

Prepubertal gonadectomy in cats: different injectable anaesthetic combinations and comparison with gonadectomy at traditional age

Anaesthetic and analgesic effects of three different injectable anaesthetic combinations for prepubertal gonadectomy (PPG) in cats were studied. One anaesthetic protocol was compared with a similar one for gonadectomy at traditional age (TAG). Kittens were randomly assigned to PPG or TAG. For PPG, three different protocols were compared: (1) intramuscular (IM) administration of 60 μg/kg dexmedetomidine plus 20 μg/kg buprenorphine followed by an IM injection of the anaesthetic agent (20 mg/kg ketamine) (DB-IM protocol); (2) oral transmucosal (OTM) administration of 80 μg/kg dexmedetomidine plus 20 μg/kg buprenorphine followed by an IM injection of 20 mg/kg ketamine combined with 20 µg/kg dexmedetomidine (DB-OTM protocol); (3) IM injection of a 40 μg/kg medetomidine-20 μg/kg buprenorphine-20 mg/kg ketamine combination (MBK-IM protocol). For TAG, a DB-IM protocol was used, but with different doses for dexmedetomidine (40 μg/kg) and ketamine (5 mg/kg). All cats (PPG and TAG) received a non-steroidal anti-inflammatory before surgery. Anaesthetic and analgesic effects were assessed pre- and postoperatively (until 6 h). Cumulative logit, linear and logistic regression models were used for statistical analysis. Compared with the DB-OTM protocol, the DB-IM and MBK-IM protocols provided better anaesthesia with fewer adverse effects in PPG cats. Postoperative pain was not significantly different between anaesthetic protocols. PPG and TAG cats anaesthetised with the two DB-IM protocols differed significantly only for sedation and pain scores, but sedation and pain scores were generally low. Although there were no anaesthesia-related mortalities in the present study and all anaesthetic protocols for PPG in cats provided a surgical plane of anaesthesia and analgesia up to 6 h postoperatively, our findings were in favour of the intramuscular (DB-IM and MBK-IM) protocols.

A review of the studies using buprenorphine in cats

Pain management is a crucial component of feline medicine and surgery. This review critically evaluates studies using buprenorphine in cats and highlights the clinical application of the opioid in this species. The pharmacokinetic-pharmacodynamic (PK-PD) modeling of IV buprenorphine has been best described by a combined effect compartmental/receptor association-dissociation model with negative hysteresis. Therefore, plasma concentrations of the drug are not correlated with analgesia, and clinicians should not expect to observe pain relief immediately after drug administration. In addition, a ceiling effect has not been demonstrated after administration of clinical doses of buprenorphine in cats; dosages of up to 0.04 mg/kg have been reported. The route of administration influences the onset, duration, and magnitude of antinociception and analgesia when using this drug in cats. At clinical dosages, the SC route of administration does not appear to provide adequate antinociception and analgesia whereas the buccal route has produced inconsistent results. Intravenous or IM administration at a dosage of 0.02-0.04 mg/kg is the preferred for treatment of pain in the acute setting. A literature search found 14 clinical trials evaluating buprenorphine sedation, analgesia, or both in cats. There were 22 original research studies reporting the antinociceptive effects of buprenorphine by means of thermal threshold, mechanical threshold, or both, minimal alveolar concentration, or PK-PD. Individual variability in response to buprenorphine administration has been reported, indicating that buprenorphine may not provide sufficient analgesia in some cats. Pain assessment is important when evaluating the efficacy of buprenorphine and determining whether additional analgesic treatment is needed.