A review of the studies using buprenorphine in cats

Dysphagia as a Missing Link Between Post-surgical- and Opioid-Related Pneumonia

PURPOSE

Postoperative pneumonia remains a common complication of surgery, despite increased attention. The purpose of our study was to determine the effects of routine surgery and post-surgical opioid administration on airway protection risk.

METHODS

Eight healthy adult cats were evaluated to determine changes in airway protection status and for evidence of dysphagia in two experiments. (1) In four female cats, airway protection status was tracked following routine abdominal surgery (spay surgery) plus low-dose opioid administration (buprenorphine 0.015 mg/kg, IM, q8-12 h; n = 5). (2) Using a cross-over design, four naive cats (2 male, 2 female) were treated with moderate-dose (0.02 mg/kg) or high-dose (0.04 mg/kg) buprenorphine (IM, q8-12 h; n = 5).

RESULTS

Airway protection was significantly affected in both experiments, but the most severe deficits occurred post-surgically as 75% of the animals exhibited silent aspiration.

CONCLUSION

Oropharyngeal swallow is impaired by the partial mu-opioid receptor agonist buprenorphine, most remarkably in the postoperative setting. These findings have implications for the prevention and management of aspiration pneumonia in vulnerable populations.

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.

Pharmacokinetics of buprenorphine and its metabolite norbuprenorphine in neutered male cats anesthetized with isoflurane

OBJECTIVE

To characterize the pharmacokinetics of buprenorphine and norbuprenorphine in isoflurane-anesthetized cats.

STUDY DESIGN

Prospective experimental study.

ANIMALS

A group of six healthy adult male neutered cats.

METHODS

Cats were anesthetized with isoflurane in oxygen. Catheters were placed in a jugular vein for blood sampling and in a medial saphenous vein for buprenorphine and lactated Ringer's solution administration. Buprenorphine hydrochloride (40 μg kg^-1 over 5 minutes) was administered intravenously. Blood samples were collected before buprenorphine administration and at various times up to 12 hours after administration. Plasma buprenorphine and norbuprenorphine concentrations were measured using liquid chromatography/tandem mass spectrometry. Compartment models were fitted to the time-concentration data using nonlinear mixed effect (population) modeling.

RESULTS

A five-compartment model (three compartments for buprenorphine and two compartments for norbuprenorphine) best fitted the data. Typical value (% interindividual variability) for the three buprenorphine volumes of distribution, and the metabolic clearance to norbuprenorphine, the remaining metabolic clearance and the two distribution clearances were 157 (33), 759 (34) and 1432 (43) mL kg^-1, and 5.3 (33), 16.4 (11), 58.7 (27) and 6.0 (not estimated) mL minute^-1 kg^-1, respectively. Typical values (% interindividual variability) for the two norbuprenorphine volumes of distribution, and the norbuprenorphine metabolic and distribution clearances were 1437 (30) and 8428 (not estimated) mL kg^-1 and 48.4 (68) and 235.9 (not estimated) mL minute^-1 kg^-1, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

The pharmacokinetics of buprenorphine in isoflurane-anesthetized cats were characterized by a medium clearance.

Single-dose pharmacokinetics and bioavailability of a novel extended duration transdermal buprenorphine solution in cats

A novel transdermal buprenorphine solution (TBS) was developed for evaluation in order to make available an extended duration opioid analgesic for cats. Healthy adult cats were administered a single TBS dose of 10 mg (1.57-4.35 mg/kg), 30 mg (4.72-13.0 mg/kg), or 50 mg (7.87-21.7 mg/kg) (4 cats per group) applied topically to the unclipped dorsal cervical skin and plasma buprenorphine concentrations were evaluated through 7 days. To determine the absolute bioavailability of TBS, healthy cats were administered single TBS dose of 20 mg (3.33-4.76 mg/kg) or 0.05 mg (0.008-0.011 mg/kg) IV buprenorphine (6 cats per group). The mean ± standard deviation maximum plasma buprenorphine concentrations (C_max ) were 10.5 ± 6.28, 18.6 ± 8.68, and 22.5 ± 4.47 ng/ml following 10, 30, and 50 mg doses, respectively, with the time of C_max occurrence (t_max ) typically occurring at 2-12 h post-dosing. Mean plasma buprenorphine terminal half-lives ranged between 78.3 and 91.2 h. Increasing the dose threefold and fivefold from the 10 mg dose increased the exposure by 2.8- and 3.6-fold, respectively, indicating that plasma buprenorphine exposure increased in a less than proportional manner at doses >30 mg. Transient sedation, mydriasis, and euphoria were observed within 4 h post-dosing. Mean rectal temperatures were increased 0.6-0.9°C greater than baseline (37.4-37.8°C) through 168 h post-dosing. The absolute bioavailability was 16.0% (90% CI: [11.8%-21.7%]). Flip-flop pharmacokinetics were observed with a terminal elimination half-life of 0.82 ± 0.13 and 64.9 ± 15.0 h for IV buprenorphine and 20 mg of TBS, respectively. A single administration of TBS over a range of doses resulted in extended plasma buprenorphine concentrations and opioid physiological and behavioral effects.

Multicentered masked placebo-controlled phase 3 clinical study of an extended duration transdermal buprenorphine solution for post-operative pain in cats

A prospective, double masked, placebo-controlled, multicentered phase 3 clinical study was conducted to evaluate the safety and effectiveness of transdermal buprenorphine solution (TBS) for the control of post-operative pain in cats. A total of 228 cats from 12 US investigational sites met the enrollment criteria of which 107 placebo- and 112 TBS-treated cats were included into the per protocol efficacy analysis. The dose of TBS was 8 mg (0.4 ml) to cats 1.2 to 3 kilograms and 20 mg (1 ml) to cats >3 to 7.5 kilograms applied topically to the dorsal unclipped cervical skin 1-2 h prior to the undergoing elective surgical reproductive sterilization in conjunction with forelimb onychectomy. Interactive pain assessments and physiological variables were quantified through 96 h following recovery from anesthesia, and rescue analgesia was administered any time that pain control was scored inadequate. Cats requiring rescue analgesia or experiencing an adverse event suspected to be treatment related were considered treatment failures. Sixty-five and 23 cats were considered treatment failures in the placebo and TBS groups, respectively, with most occurring on the day of surgery. The treatment success rates were 0.40 (95% confidence interval [CI]: [0.28-0.53]) and 0.81 (95% CI: [0.70-0.89]) in the placebo and TBS groups, respectively, and the difference was significant (p < .05). Adverse events occurred at a similar frequency and were not clinically meaningful in either treatment group. The post-operative body temperatures over the duration of the study were on average 0.35 (95% CI: [0.20-0.50]) °C higher than baseline in TBS-treated cats and were not clinically meaningful, an observation typical of opioids in cats. These results serve as substantial evidence that TBS is safe and effective for the control of orthopedic and soft tissue post-operative pain in cats when a single topical dose is applied 1-2 h prior to surgery.

Multicentered masked placebo-controlled phase 2 clinical study of an extended duration transdermal buprenorphine solution for postoperative pain in cats

A prospective, double-masked, placebo-controlled, multicentered phase 2 clinical study was conducted to select the transdermal buprenorphine solution (TBS) dosage for the control of postoperative pain in cats. One-hundred fifteen (115) cats were randomized to a single topical dose of placebo solution, low-TBS dosage (1.91-2.07 mg/kg) or high-TBS dosage (4.27-4.88 mg/kg) prior to surgical reproductive sterilization in conjunction with forelimb onychectomy. The low- and high-TBS doses were applied 2-4 and 1-2 hours prior to surgery. Interactive pain assessments and physiological variables were quantified through 96 hours post-anesthetic recovery and rescue analgesia was administered any time that analgesia was considered inadequate. Cats requiring rescue analgesia were considered treatment failures. The estimated overall treatment success rates from generalized linear mixed effects model analysis were 0.10 (95% CI: [0.02-0.36]), 0.56 (95% CI: [0.25-0.83]), 0.71 (95% CI: [0.38-0.91]) in the placebo-, low-, and high-TBS dose groups, respectively. Success rates for both TBS treatment groups were superior to placebo. Adverse events were infrequent in all treatment groups although the postoperative body temperatures over the duration of the study were on average 0.31 (95% CI: [0.08-0.55]) and 0.30 (95% CI: [0.05-0.53]) °C higher in low- and high-TBS dose cats, respectively, compared to placebo. It is concluded that both the low- and high-TBS dosages were safe and effective. The high-TBS dosage resulted in a greater proportion of treatment successes over 96 h, had a more acceptable preoperative application time of 1-2 h prior to surgery, and was therefore selected for further study.

Use of mechanical thresholds in a model of feline clinical acute pain and their correlation with the Glasgow Feline Composite Measure Pain Scale scores

OBJECTIVES

The aim of this study was to evaluate the use of mechanical thresholds (MT), measured with the SMALGO (Small Animal ALGOmeter), and to determine whether there was a correlation between MT and Glasgow Feline Composite Measure Pain Scale (CMPS-Feline) scores in cats undergoing ovariohysterectomy.

METHODS

Client-owned cats undergoing flank ovariohysterectomy were recruited. Pain scores for the pre- and postoperative periods were obtained using the CMPS-Feline in each cat by two independent investigators (A and B). Following CMPS-Feline scoring, MT were measured with the SMALGO, in the surgical area, pre- and postoperatively, only by investigator A. Each cat served as its own control for the comparison of pre- and postoperative variables. Reliability statistics were used to assess the level of inter-observer agreement (A vs B) with respect to pre- and postoperative CMPS-Feline scores, while Spearman's correlation statistics were used to analyse the relationship between MT and CMPS-Feline scores.

RESULTS

Twenty-nine cats completed the study. Preoperative MT (340 g [range 108-691]) were significantly higher than postoperatively (233 g [range 19-549]; P = 0.001). CMPS-Feline scores were not found to differ significantly between the preoperative period (2 [range 0-7] for investigator A and 3.2 ± 2.3 for investigator B) and postoperative period (2 [range 0-10] for investigator A and 3 [range 0-8] for investigator B) for either investigator. Reliability statistics revealed that the level of inter-observer agreement with respect to CMPS-Feline was fair for the preoperative assessments but poor for the postoperative evaluations. There was no correlation between MT and CMPS-Feline scores.

CONCLUSIONS AND RELEVANCE

Although there was no correlation with CMPS-Feline scores performed at the same timepoint, MT increased postoperatively vs baseline. Assuming that, despite analgesia, susceptibility of the surgical area to mechanical stimulation would increase after surgery, this finding suggests that MT might be useful to assess feline surgical pain. The poor level of inter-observer agreement with respect to postoperative CMPS-Feline scores highlights the potential limitations of this scale.

Occurrence and clinical management of urethral obstruction in male cats under primary veterinary care in the United Kingdom in 2016

Background

Urethral obstruction (UO) has a negative effect on welfare of cats.

Objectives

This study aimed to determine incidence, case management, and outcomes of UO in cats in primary‐care practice in the United Kingdom.

Animals

All male cats under veterinary care within the VetCompass database in 2016.

Methods

A retrospective cohort study was performed. The electronic records of all male cats with a clinical note during the study period were searched for UO cases and were manually reviewed for inclusion. Additional demographic and clinical information were extracted on cases.

Results

From the study cohort of 237 825 male cats, there were 1293 incident cases. The estimated UO incidence risk during 2016 was 0.54 (95% CI: 0.51‐0.57). Demographic and clinical data were available for 1108 cases. Antibiotics were administered to 641/1108 (57.9%) cases. Overall repeat catheterization rate was 253/854 (29.6%). Repeat catheterization at 48 hours was less frequent in patients with indwelling catheters (10.1%) vs those that had a catheter placed and then immediately removed (14.8%; P = .04). Death during a UO episode was 329/1108 (29.6%), and 285/329 (88.0%) deaths involved euthanasia.

Conclusions and Clinical Importance

Antibiotics were commonly prescribed in cats for treatment of UO despite minimal evidence in the clinical records of bacterial cystitis. Repeat catheterization was common and case fatality rate during a UO episode was high. Repeat catheterization within 48 hours of elective removal of a urethral catheter was less common in cats that had previously had indwelling catheters. The majority of cats requiring repeat catheterization survived until the end of the study.

2022 ISFM Consensus Guidelines on the Management of Acute Pain in Cats

PRACTICAL RELEVANCE

Increases in cat ownership worldwide mean more cats are requiring veterinary care. Illness, trauma and surgery can result in acute pain, and effective management of pain is required for optimal feline welfare (ie, physical health and mental wellbeing). Validated pain assessment tools are available and pain management plans for the individual patient should incorporate pharmacological and non-pharmacological therapy. Preventive and multimodal analgesia, including local anaesthesia, are important principles of pain management, and the choice of analgesic drugs should take into account the type, severity and duration of pain, presence of comorbidities and avoidance of adverse effects. Nursing care, environmental modifications and cat friendly handling are likewise pivotal to the pain management plan, as is a team approach, involving the cat carer.

CLINICAL CHALLENGES

Pain has traditionally been under-recognised in cats. Pain assessment tools are not widely implemented, and signs of pain in this species may be subtle. The unique challenges of feline metabolism and comorbidities may lead to undertreatment of pain and the development of peripheral and central sensitisation. Lack of availability or experience with various analgesic drugs may compromise effective pain management.

EVIDENCE BASE

These Guidelines have been created by a panel of experts and the International Society of Feline Medicine (ISFM) based on the available literature and the authors' experience. They are aimed at general practitioners to assist in the assessment, prevention and management of acute pain in feline patients, and to provide a practical guide to selection and dosing of effective analgesic agents.

The thermal antinociceptive effects of a high-concentration formulation of buprenorphine alone or followed by hydromorphone in conscious cats

OBJECTIVE

To evaluate the thermal antinociceptive effects of a high-concentration formulation of buprenorphine alone or followed by hydromorphone in conscious cats.

STUDY DESIGN

Randomized, blinded, placebo-controlled crossover study design.

ANIMALS

A total of six purpose-bred, adult female ovariohysterectomized Domestic Short Hair cats.

METHODS

Cats were allocated into three treatments each consisting of two injections, subcutaneous then intravenous (IV) administration, 2 hours apart: treatment SS, two injections of 0.9% saline; treatment BS, buprenorphine (0.24 mg kg^-1, 1.8 mg mL^-1) and saline; and treatment BH, buprenorphine (0.24 mg kg^-1) and hydromorphone (0.1 mg kg^-1). Skin temperature (ST) and thermal threshold (TT) were recorded before (baseline) and for 24 hours following first injection. TT data were analyzed using mixed linear models and a Benjamini-Hochberg sequential adjustment procedure (p < 0.05).

RESULTS

There were no significant differences among treatments for baseline ST and TT values, treatment SS over time and between treatments BS and BH. Compared with baseline, TT was significantly increased at all time points in treatments BH and BS except at 2 hours in treatment BS. TT was significantly higher than SS at 3-18 hours and 4-12 hours for treatments BS and BH, respectively. Maximal increases in TT were 47.5 °C at 2 hours, 53.9 °C at 3 hours and 52.4 °C at 6 hours in treatments SS, BS and BH, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Administration of IV hydromorphone following high-concentration buprenorphine provided no additional antinociception and decreased the duration of effect when compared with high-concentration buprenorphine alone. Alternative analgesics should be considered if additional analgesia is required after administration of high-concentration buprenorphine.

Bioavailability of subcutaneous and intramuscular administrated buprenorphine in New Zealand White rabbits

Background

Buprenorphine is one of the most used analgesics for postoperative pain in rabbits. The recommended dose in rabbits (0.01–0.05 mg/kg) is the same for intravenous (IV), intramuscular (IM), and subcutaneous (SC) administration, despite lack of pharmacokinetic data. Five male and five female New Zealand White rabbits (mean ± SD body weight 3.1 ± 0.3 kg) were administered 0.05 mg/kg buprenorphine by the IV, IM and SC routes and 0.1 mg/kg by the SC route, in a cross-over design with two-week wash-out periods between treatments. Blood was collected before, and up to 8 h post buprenorphine injection, for determination of serum levels by UPHLC-MS/MS.

Results

The area under the time concentration curve (AUC_0-t) was lower after SC (398 ± 155 ng/mL/min) than IM (696 ± 168 ng/mL/min, p < 0.001) and IV (789 ± 189 ng/mL/min, p < 0.001) administration. The maximum serum concentration was lower after SC (2.2 ± 1.4 ng/mL) than after IM (11 ± 3.2 ng/mL) administration (p < 0.001). The bioavailability was lower after SC (50 ± 19%) than after IM (95 ± 21%) administration (p = 0.006). The elimination half-life was longer after SC (260 ± 120 min) than after IM (148 ± 26 min, p = 0.002) as well as IV (139 ± 33 min) injection (p < 0.001). An increase in the SC dose from 0.05 to 0.1 mg/kg resulted in an increase in the area under the time concentration curve of 50% in female (p = 0.022) and 165% in male rabbits (p < 0.001). The bioavailability did not change in the females (36 ± 14%, p = 0.6), whereas it increased in the males (71 ± 23%, p = 0.008).

Conclusions

The lower bioavailability of 0.05 mg/kg buprenorphine after SC administration could explain the lack of efficacy seen in clinical pain studies in rabbits, using this route. For immediate pain relief, IV or IM administration is therefore be recommended, whereas SC administration may be useful to sustain analgesic serum levels, once efficient pain relief has been achieved. The current data do not support an increase in dose to compensate for the lower SC bioavailability.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-020-02618-7.

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.

World Small Animal Veterinary Association Global Dental Guidelines

Dental, oral, and maxillofacial diseases are some of the most common problems in small animal veterinary practice. These conditions create significant pain as well as localized and potentially systemic infection. As such, the World Small Animal Veterinary Association (WSAVA) believes that un- and under treated oral and dental diseases pose a significant animal welfare concern. Dentistry is an area of veterinary medicine which is still widely ignored and is subject to many myths and misconceptions. Effective teaching of veterinary dentistry in the veterinary school is the key to progression in this field of veterinary medicine, and to the improvement of welfare for all our patients globally. These guidelines were developed to provide veterinarians with the information required to understand best practices for dental therapy and create realistic minimum standards of care. Using the three-tiered continuing education system of WSAVA, the guidelines make global equipment and therapeutic recommendations and highlight the anaesthetic and welfare requirements for small animal patients. This document contains information on common oral and dental pathologies, diagnostic procedures (an easily implementable and repeatable scoring system for dental health, dental radiography and radiology) and treatments (periodontal therapy, extractions). Further, there are sections on anaesthesia and pain management for dental procedures, home dental care, nutritional information, and recommendations on the role of the universities in improving veterinary dentistry. A discussion of the deleterious effects of anaesthesia free dentistry (AFD) is included, as this procedure is ineffective at best and damaging at worst. Throughout the document the negative effects of undiagnosed and/or treated dental disease on the health and well-being of our patients, and how this equates to an animal welfare issue, is discussed.

Veterinary-Prescribed Buprenorphine Ingestion in a 2-Year-Old Girl

INTRODUCTION

Ingestion of buprenorphine by young children is on the rise and can lead to life-threatening consequences and death. Exposure most often occurs when a child acquires the medication intended for adult use. However, buprenorphine is also prescribed by veterinarians and may be sent home, typically in non-child-resistant packaging, to be administered to the family pet.

CASE

A previously healthy 2-year-old girl weighing 11.36 kg was found with a 1-mL syringe containing 0.6 mg/mL of buprenorphine in her mouth. The syringe had been in a plastic bag provided to the family by their veterinarian for the family dog. She was hospitalized for 24 hours but remained asymptomatic and was discharged healthy. This type of exposure to buprenorphine has not previously been described in the literature.

CONCLUSIONS

Having this unsecured medication in the home increases the potential risk of exposure for young children and associated health consequences. Pediatricians should be aware of the potential dangers that veterinary pharmaceuticals can pose and educate parents about proper storage of medications. In addition, veterinarians should take extra precautions when dispensing these medications to pet owners with children.

Analgesia: What Makes Cats Different/Challenging and What Is Critical for Cats?

Cats have unique anatomic, physiologic, and behavioral considerations that may influence analgesia and pain management. They present specific challenges that require an individualized, feline-specific approach. This article presents an overview of recent advances in feline pain management and their differences in relation to other species and evolves on its future challenges. The main specific anatomy and physiology of the cat and how it may affect analgesia is discussed. Validated pain assessment tools including the UNESP-Botucatu Multidimensional Composite Pain Scale, Glasgow Feline Composite Measure Pain Scale, and the Feline Grimace Scale are summarized.

Clinical applicability of the Feline Grimace Scale: real-time versus image scoring and the influence of sedation and surgery

Background

The Feline Grimace Scale (FGS) is a facial expression-based scoring system for acute pain assessment in cats with reported validity using image assessment. The aims of this study were to investigate the clinical applicability of the FGS in real-time when compared with image assessment, and to evaluate the influence of sedation and surgery on FGS scores in cats.

Methods

Sixty-five female cats (age: 1.37 ± 0.9 years and body weight: 2.85 ± 0.76 kg) were included in a prospective, randomized, clinical trial. Cats were sedated with intramuscular acepromazine and buprenorphine. Following induction with propofol, anesthesia was maintained with isoflurane and cats underwent ovariohysterectomy (OVH). Pain was evaluated at baseline, 15 min after sedation, and at 0.5, 1, 2, 3, 4, 6, 8, 12 and 24 h after extubation using the FGS in real-time (FGS-RT). Cats were video-recorded simultaneously at baseline, 15 min after sedation, and at 2, 6, 12, and 24 h after extubation for subsequent image assessment (FGS-IMG), which was performed six months later by the same observer. The agreement between FGS-RT and FGS-IMG scores was calculated using the Bland & Altman method for repeated measures. The effects of sedation (baseline versus 15 min) and OVH (baseline versus 24 h) were assessed using linear mixed models. Responsiveness to the administration of rescue analgesia (FGS scores before versus one hour after) was assessed using paired t-tests.

Results

Minimal bias (-0.057) and narrow limits of agreement (-0.351 to 0.237) were observed between the FGS-IMG and FGS-RT. Scores at baseline (FGS-RT: 0.16 ± 0.13 and FGS-IMG: 0.14 ± 0.13) were not different after sedation (FGS-RT: 0.2 ± 0.15, p = 0.39 and FGS-IMG: 0.16 ± 0.15, p = 0.99) nor at 24 h after extubation (FGS-RT: 0.16 ± 0.12, p = 0.99 and FGS-IMG: 0.12 ± 0.12, p = 0.96). Thirteen cats required rescue analgesia; their FGS scores were lower one hour after analgesic administration (FGS-RT: 0.21 ± 0.18 and FGS-IMG: 0.18 ± 0.17) than before (FGS-RT: 0.47 ± 0.24, p = 0.0005 and FGS-IMG: 0.45 ± 0.19, p = 0.015).

Conclusions

Real-time assessment slightly overestimates image scoring; however, with minimal clinical impact. Sedation with acepromazine-buprenorphine and ovariohysterectomy using a balanced anesthetic protocol did not influence the FGS scores. Responsiveness to analgesic administration was observed with both the FGS-RT and FGS-IMG.

The analgesic effects of buprenorphine (Vetergesic or Simbadol) in cats undergoing dental extractions: A randomized, blinded, clinical trial

This study aimed to evaluate the analgesic efficacy of two dosage regimens using two different concentrations of buprenorphine in cats undergoing dental extractions. Twenty-three cats with oral disease (8.2 ± 2.2 years old; 4.9 ± 0.9 kg) were included in a prospective, blinded, randomized clinical trial. Cats randomly received either Simbadol (1.8 mg/mL; 0.24 mg/kg, subcutaneously, every 24h: SG, n = 11) or Vetergesic (0.3 mg/mL; 0.02 mg/kg, intramuscularly, every 8h: VG, n = 12) throughout the study. They were admitted at day 0, underwent oral examination/radiographs/treatment under general anesthesia (buprenorphine-propofol-isoflurane-meloxicam-local anesthetic blocks) at day 1 and discharged at day 4. Sedation and pain were scored using the dynamic interactive visual analog scale (day 1) and the Glasgow Composite Measure Pain Scale-Feline (CMPS-F; up to postoperative 8 hours at day 1, 8 am, 4 pm and midnight at days 2 and 3, and 8 am at day 4), respectively. Rescue analgesia was administered with hydromorphone (0.05 mg/kg intravenously on day 1 or 0.1 mg/kg intramuscularly after day 2) when CMPS-F ≥ 5. Resentment defined as any type of escape behavior associated with aversion to drug administration was recorded. Sedation and pain scores, the prevalence of rescue analgesia and resentment during drug administration were analyzed using linear mixed models and Fisher’s exact test, respectively (p < 0.05). Pain and sedation scores were not significantly different between groups. Sedation scores were significantly higher up to postoperative 2 hours in both groups. Pain scores in SG and VG were significantly higher up to postoperative 8 hours and 8 am of day 2, respectively, than baseline. Prevalence of rescue analgesia and resentment were not significantly different between groups (SG: 27.3%, VG: 33.3% and SG: 0%, VG: 25%, respectively). Simbadol produced similar analgesic effects to Vetergesic without resentment during drug administration.

The US Opioid Epidemic and Its Impact on US General Practice Veterinarians

Objective: To assess the impact of the human opioid epidemic and associated shortages in drug supply on US general practice veterinarians. Design: Cross-sectional study. Sample: Members of the Veterinary Information Network (VIN). Procedures: An electronic survey was used to examine veterinarians' views regarding opioid use in veterinary medicine and the impact of the opioid shortage on the provision of care. The survey was distributed via the VIN data collection portal from October 12-November 6, 2018. Results: 697 veterinarians completed the survey. Most (99.7%) reported using, dispensing or prescribing opioids in veterinary practice. The most commonly used opioids were buprenorphine, tramadol and butorphanol. While most veterinarians (83.3%) reported difficulty in ordering opioids over the last 6 months, this decreased to 59.0% in the last month. The most difficult drugs to obtain were hydromorphone, morphine, injectable fentanyl, and oxymorphone. The reported rate of difficulty in obtaining all these drugs lessened over time. However, the opioid shortage caused significant difficulty in providing appropriate pain management for 41.1% of participants, and affected the ability of 44.8% of respondents to provide optimal anesthesia. Conclusions and Clinical Relevance: Veterinarians' ability to provide opioids for their patients has been impacted by the opioid shortage, with a greater impact on full mu opioid agonists as compared to drugs like butorphanol, buprenorphine, and tramadol. The results confirm the important role of opioid analgesics in the delivery of modern veterinary medicine and highlight the importance of medical health professionals being able to access these critical medications.

Medical management of deep ulcerative keratitis in cats: 13 cases

CASE SERIES SUMMARY

Described are 13 cats diagnosed with deep ulcerative keratitis and successfully managed medically without grafting procedures. Typical treatment involved frequent topical application of serum and antibiotics (usually a fluoroquinolone and a cephalosporin). Seven cats also received systemic antibiotics. Analgesia was achieved using various combinations of topical atropine and systemic buprenorphine, robenacoxib or corticosteroids. Six cats were hospitalized for a median (range) period of 2.5 (1-8) days, typically because of frequent medication administration. Median (range) follow-up time was 41.5 (9-103) days. Median (range) number of recheck examinations was 4 (2-6). Median (range) time to corneal re-epithelialization was 21 (9-103) days. Median (range) topical antibiotic course was 29.5 (16-103) days. Median (range) duration of Elizabethan collar use was 28 (13-73) days. At the time of writing, no further recheck examinations were recommended for 10 cats; median (range) time between initial to final examinations in these cats was 35 (20-103) days. All cats retained the affected globes and were apparently comfortable and visual at the latest recheck examination.

RELEVANCE AND NOVEL INFORMATION

These cases reveal that aggressive medical management is highly successful in select cats with deep ulcerative keratitis, and can result in a cosmetically acceptable, apparently comfortable and visual globe. However, therapy is intensive with frequent administration of multiple topical and sometimes systemic medications, and requires multiple veterinary visits over many weeks. Referral to a veterinary ophthalmologist for consideration of surgical stabilization is recommended, as not all cases may be amenable to the medical therapy described here.

The analgesic effects of buprenorphine (Vetergesic or Simbadol) in combination with carprofen in dogs undergoing ovariohysterectomy: a randomized, blinded, clinical trial

Background

Buprenorphine is a potent lipophilic opioid analgesic that is largely used in the multimodal treatment of acute pain. Simbadol (buprenorphine hydrochloride) is the first and only FDA-approved high-concentration formulation of buprenorphine for use in cats. The aim of this study was to evaluate the analgesic efficacy of carprofen in combination with one of two commercial formulations of buprenorphine (Simbadol and Vetergesic, 1.8 mg/mL and 0.3 mg/mL, respectively) in dogs undergoing ovariohysterectomy. Twenty-four dogs were included in a randomized, prospective, controlled, clinical trial. Patients were randomly divided into 2 groups as follows. Dogs were premedicated with acepromazine (0.02 mg/kg) and either 0.02 mg/kg of Vetergesic or Simbadol intramuscularly (Vetergesic group – VG; Simbadol group – SG, respectively; n = 12/group). General anesthesia was induced with propofol and maintained with isoflurane in 100% oxygen. Carprofen (4.4 mg/kg SC) was administered after induction of anesthesia. Heart rate, respiratory rate, blood pressure, pulse oximetry, pain scores using the Glasgow Composite Pain Scale Short Form (CMPS-SF), sedation scores using a dynamic interactive visual analogue scale and adverse events were evaluated before and after ovariohysterectomy by an observer who was unaware of treatment administration. If CMPS-SF scores were ≥ 5/20, dogs were administered rescue analgesia (morphine 0.5 mg/kg IM). Statistical analysis was performed using linear mixed models and Fisher’s exact test (p < 0.05).

Results

Pain and sedation scores and physiological parameters were not significantly different between treatments. Three dogs in VG (25%) and none in SG (0%) required rescue analgesia (p = 0.109). Adverse effects (i.e. vomiting and melena) were observed in two dogs in SG and were thought to be related to stress and/or nonsteroidal anti-inflammatory drug toxicity.

Conclusions

The administration of buprenorphine with carprofen preoperatively provided adequate postoperative analgesia for the majority of dogs undergoing OVH without serious adverse events. Prevalence of rescue analgesia was not significantly different between groups; however, it could be clinically relevant and explained by a type II error (i.e. small sample size). Future studies are necessary to determine if analgesic efficacy after Simbadol and Vetergesic is related to individual variability or pharmacokinetic differences.

Robenacoxib in the treatment of pain in cats and dogs: safety, efficacy, and place in therapy

Robenacoxib is a novel nonsteroidal anti-inflammatory drug (NSAID) of coxib class developed for the control of inflammation and pain in dogs and cats. It shows high selectivity for the cyclooxygenase-2 (COX-2) enzyme in rats, cats, and dogs. Robenacoxib is available in both injectable and tablet formulations. This review initially focuses on the preclinical pharmacology of robenacoxib in rats that includes its high affinity for COX-2 enzyme and weaker and rapidly reversible binding for COX-1 enzyme in in vitro and ex vivo models of inflammation and its pharmacokinetics in the blood and inflammatory exudate, selective tissue distribution, and safety. These basic pharmacological profiles highlight the suitability of robenacoxib for use in target species, such as cats and dogs. Since the level of expression and activity of COX enzymes is species specific, COX-2-selective inhibition and the resultant effects of coxibs must be studied in target species. The pharmacological and toxicological profiles of robenacoxib in cats and dogs have been discussed prior to reviewing its clinical efficacy and safety. Large, multicenter field trials conducted in cats and dogs demonstrated the noninferior efficacy and safety of robenacoxib compared with noncoxib NSAIDs used in dogs and cats. These trials investigated the efficacy of robenacoxib against various acute and chronic painful conditions. Robenacoxib produced superior efficacy to placebo and COX-2 preferential inhibitors in postsurgical cats. The tissue-selective anti-inflammatory activity of robenacoxib has been demonstrated in dogs with osteoarthritis. Robenacoxib has also been shown to be safe in healthy dogs and cats receiving antihypertensive drugs and loop diuretics that could cause renal injury. The developmental objective of coxibs, comparable efficacy but superior safety to less selective/nonselective NSAIDs, is well established with robenacoxib in preclinical studies. More studies need to be conducted to fully explore the benefits of robenacoxib in clinical subjects.

Evaluation of analgesic effect and absorption of buprenorphine after buccal administration in cats with oral disease

Objectives The objective of this study was to evaluate the analgesic effect and absorption of buprenorphine after buccal administration in cats with oral disease. Methods Six adult client-owned cats with chronic gingivostomatitis (weighing 5.1 ± 1.1 kg) were recruited for a randomised, prospective, blinded, saline-controlled, crossover study. Pain scores, dental examination, stomatitis score and buccal pH measurement were conducted on day 1 under sedation in all cats. On day 2, animals were randomised into two groups and administered one of the two treatments buccally (group A received buprenorphine 0.02 mg/kg and group B received 0.9% saline) and vice versa on day 3. Pain scores and food consumption were measured at 30, 90 and 360 mins after the administration of buprenorphine. Blood samples were taken at the same time and plasma buprenorphine concentration was measured by liquid chromatography-mass spectrometry. Data were statistically analysed as non-parametric and the level of significance was set as P <0.05. Results There were no major side effects after buprenorphine administration. Buccal pH values ranged between 8.5 and 9.1 and the stomatitis disease activity index between 10 and 22 (17.8 ± 4.5), with the scale ranging from 0-30. The maximum buprenorphine plasma concentration (14.8 ng/ml) was observed 30 mins after administration and there was low inter-individual variability. There was a significant difference between baseline pain scores compared with pain scores after buprenorphine ( P <0.05), and between the saline and buprenorphine group at 30 mins ( P = 0.04) and 90 mins ( P = 0.04). There was also a significant effect of the stomatitis index on the pain score. Regarding the pharmacokinetic parameters, cats with stomatitis showed lower bioavailability and shorter absorption half-life after buccal administration of buprenorphine compared with normal cats in previous studies. Conclusions and relevance Buccal administration of buprenorphine in cats with gingivostomatitis produces an analgesic effect and low inter-individual variability in plasma concentration, and it can be incorporated in their multimodal analgesia plan.

Analgesic Efficacy and Safety of Buprenorphine in Chinchillas (Chinchilla lanigera)

Buprenorphine is routinely used in chinchillas at reported doses of 0.01 to 0.1 mg/kg IM or SC. However, these dose recommendations are based on anecdotal reports or extrapolation from studies in other species. Therefore, the purpose of this study was to evaluate the analgesic efficacy and safety of subcutaneously administered buprenorphine in chinchillas. Using a randomized, blind, controlled, complete crossover design, we evaluated buprenorphine at a single dose of 0.05, 0.1 or 0.2 mg/kg SC (experiment A) and 0.2 mg/kg SC (experiment B). Analgesic efficacy was determined by measuring limb withdrawal latencies in response to a thermal noxious stimulus (Hargreaves method) at 0, 3, 6, 12, and 24 h (experiment A) and at 0, 1, 2, 4, and 8 h (experiment B). In a third experiment, food intake and fecal output were monitored after repeated administration of buprenorphine (0.2 mg/kg SC every 6 h for 3 doses). Buprenorphine at 0.2 mg/kg SC, but not at 0.05 or 0.1 mg/kg SC, significantly increased limb withdrawal latencies for less than 4 h. Self-limiting reduction in food intake and fecal output occurred after administration at the 0.2-mg/kg dose in animals undergoing algesiometry. In chinchillas not undergoing algesiometry, the administration of 3 doses at 0.2 mg/kg SC every 6 h did not reduce food intake but significantly decreased fecal output for the first 24 h. Additional studies are needed to evaluate buprenorphine in different algesiometry models and to establish its pharmacokinetic profile in chinchillas.

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.

Buprenorphine Alters Inflammatory and Oxidative Stress Molecular Markers in Arthritis

Buprenorphine is recommended for use as an analgesic in animal models including in murine models of collagen-induced arthritis (CIA). However, the effect of buprenorphine on the expression of disease-associated biomarkers is not well defined. We examined the effect of buprenorphine administration on disease progression and the expression of inflammatory and oxidative stress markers, in a murine model of CIA. Buprenorphine administration altered the expression of cytokines, IFN-γ, IL-6, and MMP-3, and oxidative markers, for example, iNOS, superoxide dismutase (SOD1), and catalase (CAT), in the CIA mice. As buprenorphine is an analgesic, we further monitored the association of expression of these biomarkers with pain scores in a human cohort of early rheumatoid arthritis (RA). Serum MMP-3 levels and blood mRNA expression of antioxidants sod1 and cat correlated with pain scores in the RA cohort. We have demonstrated that administration of buprenorphine alters the expression of inflammatory and oxidative stress-related molecular markers in a murine model of CIA. This caveat needs to be considered in animal experiments using buprenorphine as an analgesic, as it can be a confounding factor in murine studies used for prediction of response to therapy. Furthermore, the antioxidant enzymes that showed an association with pain scores in the human cohort may be explored as biomarkers for pain in future studies.

Pharmacokinetic and pharmacodynamic modelling after subcutaneous, intravenous and buccal administration of a high-concentration formulation of buprenorphine in conscious cats

Background

The aim of this study was to describe the joint pharmacokinetic-pharmacodynamic model and evaluate thermal antinociception of a high-concentration formulation of buprenorphine (Simbadol^™) in cats.

Methods

Six healthy cats (4.9 ± 0.7 kg) were included in a prospective, randomized, blinded, crossover study. Simbadol^™ (1.8 mg mL^-1) was administered by the subcutaneous (SC; 0.24 mg kg^-1), intravenous (IV; 0.12 mg kg^-1) or buccal (OTM; 0.12 mg kg^-1) route of administration and thermal thresholds (TT) were compared with a saline group (SAL). Thermal threshold testing and blood sampling were performed at predetermined time points up to 72 hours including a placebo group. Plasma buprenorphine and norbuprenorphine concentrations were measured using liquid chromatography mass spectrometry. A bespoke bicompartmental pharmacokinetic model simultaneously fitted data from two analytes/three routes of administration. Temporal changes in TT were analyzed using one-way ANOVA followed by Dunnett’s test and treatment comparisons using two-way ANOVA with Bonferroni’s correction (P < 0.05).

Results

Thermal thresholds were significantly increased after SC, IV and OTM from 1–24 hours (except 2 hours), 0.5–8 hours (except 6 hours), and 1–8 hours (except 6 hours), respectively, when compared with baseline. Thermal thresholds were significantly increased after SC (1–30 hours), IV (1–8 hours) and OTM (1–12 hours) when compared with SAL, but not different among buprenorphine-treated cats. The absolute buprenorphine clearance was 0.98 L kg^-1 hour^-1, volume of distribution at steady state was 7.9 L kg^-1 and the elimination-half-life was 12.3 hours. Bioavailability for SC and OTM was 94% and 24%, respectively. Subcutaneous absorption was biphasic. An initial peak (0.08 hours) was followed by a slow (half-life 11.2 hours) and progressive (peak acceleration at 2.8 hours) uptake.

Conclusion

The SC administration of Simbadol^™ was characterized by prolonged absorption half-life and sustained plasma concentrations yielding long-lasting antinociception (≥ 24 hours) when compared with the IV and OTM routes.

Pilot evaluation of a novel unilateral onychectomy model and efficacy of an extended release buprenorphine product

Background

Non-steroidal anti-inflammatory drugs (NSAIDs), transdermal fentanyl patches, and transmucosal buprenorphine are probably the most commonly used options for providing post-operative analgesia in the early at-home period. However, these require daily administration or are associated with abuse concerns. One of the significant unmet needs in veterinary surgery and pain management is for longer acting opioids for cats to effectively bridge the gap between the in-hospital and at-home recovery periods.

A proof of concept study of an extended release formulation of buprenorphine HCL (ER-Bup) was conducted using objective kinetic measures and a unilateral onychectomy model. Using a blinded, randomized, two period crossover design, four cats were allocated to control (saline) or ER-Bup (0.6 mg/kg, subcutaneously [SC]) treatment groups. All animals underwent a unilateral forelimb onychectomy per period with a washout/recovery period in between. Observational pain scores and kinetic data (using a pressure sensitive walkway [PSW]) were collected prior to (baseline) and at intervals for 72 h following surgery. Symmetry indices were derived for kinetic variables (peak vertical force [PVF]; vertical impulse [VI]) of each forelimb for landing following a jump and for walking. A rescue analgesic protocol was in place. Effect of surgery and treatment were evaluated using a mixed model statistical approach.

Results

No cats required rescue analgesics based on subjective pain score. ER-Bup had a positive influence on subjective pain scores during the 72 h postsurgery (p = 0.0473). PVF and VI of the operated limb were significantly decreased for both landing (p < 0.0001 and p < 0.0001) and walking (p < 0.0001 and p < 0.0001 respectively) compared to control. ER-Bup resulted in significantly decreased asymmetry in limb use during landing (PVF, p < 0.0001; VI, p < 0.0001) and walking (PVF, p = 0.0002, VI, p < 0.0001). The novel use of data collected following a jump from an elevated platform appeared to provide all desired information and was easier to collect than walking data.

Conclusion

This study demonstrates that SC administration of ER-Bup may be an effective analgesic for a 72 h period postoperatively. Furthermore, landing onto a PSW from an elevated perch may be a useful and efficient way to assess analgesics in cats using a unilateral model of limb pain.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-0943-5) contains supplementary material, which is available to authorized users.

Antinociceptive effects of intravenous administration of hydromorphone hydrochloride alone or followed by buprenorphine hydrochloride or butorphanol tartrate to healthy conscious cats

OBJECTIVE

To evaluate antinociceptive effects of IV administration of hydromorphone alone or followed by buprenorphine or butorphanol to cats.

ANIMALS

6 healthy adult cats.

PROCEDURES

In a randomized, blinded crossover design, cats received each of 4 treatments in which 2 IV injections were given 30 minutes apart: 2 of saline (0.9% NaCl) solution (Sal-Sal) or 1 each of hydromorphone HCl and saline solution (H-Sal), hydromorphone and buprenorphine HCl (H-Bupre), or hydromorphone and butorphanol tartrate (H-Butor). Skin temperature and thermal threshold were recorded before (baseline) and for 12 hours after the first injection. Percentage of maximum possible effect (%MPE) and thermal excursion (TE) were compared among treatments and measurement points.

RESULTS

Compared with baseline values, skin temperature was higher from 0.75 to 2 hours after the first injection for H-Sal; at 0.5, 1, 3, and 4 hours for H-Bupre; from 0.5 to 3 hours for H-Butor; and from 0.5 to 1 hours for Sal-Sal. Thermal excursion was higher than at baseline from 0.25 to 2 hours for H-Sal and H-Bupre and 0.25 to 0.75 hours for H-Butor; %MPE increased from 0.25 to 2 hours for H-Sal, 0.25 to 3 hours for H-Bupre, and 0.25 to 0.75 hours for H-Butor. Results were similar for comparisons with Sal-Sal, except TE was greater for H-Sal versus Sal-Sal and TE and %MPE were greater for H-Bupre versus Sal-Sal from 0.25 to 1 hours after the first injection.

CONCLUSIONS AND CLINICAL RELEVANCE

Butorphanol administration decreased the duration of antinociception achieved with hydromorphone administration in cats. This opioid interaction and its impact on pain management require additional investigation.

Preliminary investigation of the thermal antinociceptive effects of codeine in cats

OBJECTIVES

The aim of this study was to evaluate the potential thermal antinociceptive effects of oral administration of a single dose of codeine in cats compared with positive (buprenorphine) and negative (saline 0.9%) controls.

METHODS

Six adult healthy cats weighing 5.14 ± 0.6 kg were used. Skin temperature and thermal thresholds (TTs) were evaluated using a wireless device (Topcat Metrology) at baseline, 0.5, 1, 3, 6 and 10 h after treatment. In period 1, TTs were evaluated after subcutaneous administration of saline 0.9%. In period 2, cats were administered either oral codeine (10 mg total, 2.0 ± 0.2 mg/kg) or buccal buprenorphine (0.04 mg/kg) in a cross-over, blinded study design. Half of the volume of buprenorphine was administered into each cheek pouch. Δ TT (difference between TTs after and before treatment) was used for data comparison. Mean ± SD data were analyzed using one-way ANOVA followed by Dunnett's or Tukey's test when appropriate (P <0.05).

RESULTS

Adverse effects did not occur in any group. Skin temperature was not different between groups nor over time. Temporal changes in TTs were not observed after saline or codeine. Buprenorphine increased Δ TT at 3 h (2.7 ± 3.3°C) when compared with baseline or saline (P <0.05). For buprenorphine, TTs were not >47.6°C at any time point in four cats. The mean highest temperature recorded in the two other cats in that group was 54.5 and 52.8°C at 3 h.

CONCLUSIONS AND CLINICAL RELEVANCE

At the dose administered, codeine did not produce thermal antinociception. Mild increases in TT after buccal buprenorphine might be related to the first-pass effect after drug swallowing, drug spillage during administration and/or individual variability. These factors should be taken in to consideration when administering buprenorphine by this route in the clinical setting.

Beyond-use date determination of buprenorphine buccal solution using a stability-indicating high-performance liquid chromatographic assay

OBJECTIVES

The objectives of this study included developing and validating a stability-indicating high-performance liquid chromatographic (HPLC) method with ultraviolet (UV) detection for the determination of buprenorphine in a buccal solution for veterinary use, and applying that method to determine the stability of a 3 mg/ml buprenorphine preparation in room temperature and refrigerated storage conditions. This preparation, intended for buccal administration in feline patients, plays an important role in pain management in cats.

METHODS

A stability-indicating HPLC method was developed and validated for system suitability, accuracy, repeatability, intermediate precision, specificity, linearity and robustness based on US Pharmacopeia (USP) General Chapter <1225>. The method was then applied to the study of potency changes over 90 days in a buccal buprenorphine solution stored at two temperatures.

RESULTS

All HPLC-UV method data met acceptable criteria for the quantification of buprenorphine in a buccal solution formulation. The buprenorphine concentrations found in each stability sample remained within the 90-110% of label claim throughout the 90 days of study. All stability test bottles of the buprenorphine buccal solution retained their original appearance. For the room temperature bottles, some white particulate matter was noted in the threads of the container bottles starting at day 21. The pH of the preparations during the course of the study was in the range of 3.57-4.06 and 4.01-4.16 for the room temperature and refrigerated samples, respectively.

CONCLUSIONS AND RELEVANCE

Pharmacists have compounded a concentrated 3 mg/ml buccal solution to use easily in the home care or outpatient setting for treatment of feline pain. Prior to this investigation, pharmacists empirically assigned beyond-use dates to this formulation based on standards in USP General Chapter <795> Pharmaceutical Compounding - Nonsterile Preparations. This study of a 3 mg/ml buprenorphine buccal solution indicates stability through 90 days.

Contrast-enhanced ultrasound of both kidneys in healthy, non-anaesthetized cats

Background

Changes in perfusion are considered to play a key role in the pathophysiology of renal disease. Contrast-enhanced ultrasound (CEUS) has shown a promising diagnostic imaging technique to non-invasively and repetitively quantify tissue perfusion. Examination protocols have varied between studies regarding US equipment, quantification software, the use of sedation or anaesthesia, and animals. The purpose of the present study was, to assess the feasibility of a standardized CEUS protocol for perfusion analysis of both kidneys in nine healthy, non-anaesthetized cats.

Results

CEUS was fairly tolerable for all but one cat. In 6/18 kidneys (2 left, 4 right), a second contrast medium injection was needed due to motion artifacts. Perfusion variables such as peak intensity (PI), wash-in slope (WI_S), wash-out slope (WO_S) and mean transit time (MTT) did not significantly differ between left and right renal cortex and medulla nor between the cranial and caudal renal cortex within each kidney. In contrast, for all kidneys, mean PI, WI_S, and MTT were significantly higher in the cortex than in the medulla (P = 0.001, 0.012 and <0.001, respectively).

Conclusions

The herein reported CEUS protocol and the perfusion measurements may serve as a baseline protocol and normal reference values for the evaluation of feline patients. However, the protocol and results may be of limited value in uncooperative animals.

Analgesia in the Perioperative Period

Untreated or undermanaged perioperative pain has systemic effects that may negatively impact a patient's welfare and return to function. A consistent analgesic plan that assesses a patient's pain and comfort at regular intervals during the perioperative period should be incorporated into practice. Validated pain assessment tools are available for use in dogs and cats. Multimodal analgesic plans should be created for individual patients and modified according to pain assessments. These plans, based on a thorough history, physical examination, and knowledge of the expected pain, should be combinations of an opioid, a nonsteroidal anti-inflammatory drug, a local anesthetic, and nonpharmacologic analgesic techniques.

Practical use of opioids in cats: a state-of-the-art, evidence-based review

RATIONALE

Recent recognition of the need to improve pain management in cats has led to the investigation of the pharmacokinetics and efficacy of opioid analgesic drugs in this species. The results of these studies may be difficult to interpret because the effect of these drugs varies with dose, route of administration and the method used to assess them. As equipotency of different opioids is not known, it is hard to compare their effects. Animals do not verbalise the pain they feel and, in cats, it may be more difficult to recognise signs of pain in comparison with other species such as dogs.

AIM

This article reviews the use of opioid analgesics in cats. It must be remembered that not all drugs are licensed for use in cats, and that marketing authorisations vary between different countries.