Clinical efficacy and pharmacokinetics of carprofen in the treatment of dogs with osteoarthritis

The effect of intravenous lipid emulsion (ILE) on the pharmacokinetic/toxicokinetic dispositions of ivermectin and carprofen in rabbits

Intravenous lipid emulsion (ILE) has been widely used as an effective antidote in both veterinary and human medicine for the treatment of acute intoxications caused by drugs and pesticides with high lipid solubility. This study was conducted to investigate the effect of ILE co-administration on the kinetic dispositions of ivermectin (IVM) and carprofen (CRP) following intravenous bolus administration at subtoxic doses in rabbits.Twenty-four male New Zealand rabbits weighing 2.78 ± 0.2 kg were used in this study. Rabbits were divided into four groups (Group 1: IVM and Group 2: IVM + ILE or Group 3: CRP and Group 4: CRP + ILE), each group consisting of 6 animals. In the IVM study, Group 1 received IVM (0.6 mg/kg) alone while Group 2 received IVM (0.6 mg/kg) and ILE (2.5 ml/kg). In the CRP study, Group 3 received CRP (12 mg/kg) alone while Group 4 received CRP (12 mg/kg) and ILE (2.5 ml/kg). In both drug groups, ILE was administered 3 times as an i.v. bolus at the 10th min and repeated 4th and 8th h after the drug administration. Blood samples were collected from the auricular vein at various times after drug administration. The drug concentrations in plasma samples were determined by high-pressure liquid chromatography. Kinetic parameters were calculated using a non-compartmental model for both CRP and IVM.The C0 and area under the concentration-time curve from zero up to ∞ (AUC0-∞) values were significantly greater with ILE co-administration (2136 ng/ml and 360.84 ng.d/ml) compared to the IVM alone (1340.63 ng/ml and 206 ng.d/ml), respectively. Moreover, the volume of distribution (Vdss) and clearance (Cl) of IVM were reduced by approximately 42% and 46% with ILE co-administration compared to IVM alone resulting in a reduction of the distribution and slower elimination, respectively. Similar differences in C0, and Vdss values were also observed in CRP with ILE co-administration compared to CRP alone. ILE co-administration changed significantly the kinetic profile of both IVM and CRP in rabbits, supporting the lipid sink theory in which highly lipid-soluble compounds are absorbed into the lipid phase of plasma from peripheral organs such as the heart and brain affected by the acute toxicity of the compounds.

DEVELOPMENT AND EVALUATION OF A STANDARDIZED SYSTEM FOR THE ASSESSMENT OF LOCOMOTOR HEALTH IN ELEPHANTS UNDER HUMAN CARE

Although lameness is a common problem in elephants (Asian elephant [Elephas maximus] and African elephants Loxodonta africana and Loxodonta cyclotis) under human care, there has not been a standardized lameness assessment system to date. This study developed and evaluated a standardized system for the assessment of locomotion in elephants under human care regardless of husbandry system. In total, 72 elephants out of a possible 73 in the United Kingdom and Ireland were filmed from behind, from in front, and from both sides. Using a questionnaire and a select panel of elephant specialists, a zoo veterinarian, and a locomotion expert, a numerical rating scoring (NRS) system was proposed. Locomotion was scored on a 4-point scale with numerical values 0-4 corresponding to specific criteria as follows: 0 = clinically sound, 1 = stiffness, 2 = abnormal tracking, and 4 = reluctance to bear weight. The intra- and interobserver repeatability of five veterinary surgeons using this system was determined and compared with a visual analog scale (VAS) expressed as a 100-mm line. Overall intraobserver reliability was moderate (Cohen's kappa [κ] = 0.676) and interobserver reliability was fair (κ = 0.37) for the presence of lameness. Interobserver agreement improved from the first scoring to second scoring from slight agreement to fair agreement for stiffness and reluctance to bear weight. Abnormal tracking had moderate intraobserver agreement for both scoring sessions. There were wide widths of agreement for the VAS interobserver (67 mm); however, they were narrower for the intraobserver (33 mm). The developed NRS can be used on freely moving elephants to evaluate elephant locomotion, regardless of husbandry methods, and has been shown to be more reliable than a VAS.

Blinded, randomized, placebo-controlled study of the efficacy of bupivacaine liposomal suspension using static bodyweight distribution and subjective pain scoring in dogs after tibial plateau leveling osteotomy surgery

OBJECTIVE

To compare the analgesic effect of surgical wound infiltration with liposomal bupivacaine (LB) to saline placebo in dogs after tibial plateau leveling osteotomy (TPLO).

STUDY DESIGN

Blinded, randomized, placebo-controlled clinical prospective study.

ANIMALS

Fifteen client-owned dogs receiving LB and 17 dogs receiving an equivalent volume of saline placebo, all with confirmed unilateral cranial cruciate ligament insufficiency.

METHODS

Preoperatively and up to 48 h after surgery, Glasgow Composite Measure Short Form (CMPS-SF) pain scores were assigned and using a weight distribution platform, static bodyweight distribution (%BW_dist ) to the operated limb was measured. Postoperatively, dogs also received carprofen 2.2 mg/kg subcutaneously every 12 h. Rescue analgesia was provided. Treatment success was defined as not requiring rescue analgesia over the 48-h postoperative period.

RESULTS

There was no difference between treatment success, postoperative opioid consumption, CMPS-SF pain scores, or %BW_dist in dogs that received surgical wound infiltration with LB compared with those receiving saline placebo, following TPLO. There was no linear correlation between CMPS-SF pain scores and %BW_dist .

CONCLUSION

For the population of dogs that underwent TPLO and received postoperative carprofen at our institution, LB did not provide an analgesic effect discernable by success/failure analysis, CMPS-SF pain scores, or %BW_dist measurement using a weight distribution platform, compared with saline placebo.

CLINICAL SIGNIFICANCE

LB may not provide detectable analgesia during the first 48 h for dogs recovering from TPLO and receiving only postoperative carprofen.

Management of Osteoarthritis and Joint Support Using Feed Supplements: A Scoping Review of Undenatured Type II Collagen and Boswellia serrata

In the multimodal management of osteoarthritis (OA) in recent decades, the use of feed supplements to maintain joint cartilage has been advocated. The aim of this scoping review is to present the results found in the veterinary literature on the use of undenatured type II collagen and Boswellia serrata in dogs, specifically its use in dogs with clinical signs of OA, healthy dogs after intense exercise or dogs with diseases that predispose the individual to OA. For this purpose, a literature review was carried out using the electronic databases PubMed, Web of Science and Google Scholar, from which a total of 26 records were included in this review: fourteen evaluating undenatured type II collagen, ten evaluating Boswellia serrata and two evaluating the combination of undenatured type II collagen and Boswellia serrata. The review of the records showed that undenatured type II collagen decreases the clinical signs associated with OA, improving the general clinical state with a reduction in the degree of lameness and increase in physical activity or mobility. Evaluating the response to supplementation with Boswellia serrata alone is complicated due to the limited publication of studies and variations in the purity and compositions of the products used, but in general terms, its combination with other feed supplements produces benefits by relieving pain and reducing the clinical signs of OA in dogs. The combination of both in the same product provides results similar to those obtained in undenatured type II collagen studies. In conclusion, undenatured type II collagen and Boswellia serrata are considered a valid option for the multimodal approach to the management of OA and for improving activity during intense exercise, but more studies are needed to conclude whether or not it prevents OA in dogs.

Swine as the Animal Model for Testing New Formulations of Anti-Inflammatory Drugs: Carprofen Pharmacokinetics and Bioavailability of the Intramuscular Route

Carprofen (CP) is a non-steroidal anti-inflammatory drug (NSAID) frequently used to treat respiratory diseases in numerous small animals, but also in large species. CP is a formidable candidate for further therapeutic research of human inflammatory diseases using the pig as an animal model. However, CP administration in swine is very uncommon and respective pharmacokinetics/bioavailability studies are scarce. A simultaneous population pharmacokinetic analysis after CP intravenous and intramuscular administrations in pigs has shown high extent and rate of absorption and a similar distribution profile with respect to man and other mammals. However, clearance and half-life values found in swine suggest a slower elimination process than that observed in man and some other animal species. Although not reported in other species, liver and kidney concentrations achieved at 48 h post-intramuscular administration in pigs were ten times lower than those found in plasma. Simulations pointed to 4 mg/kg every 24 h as the best dosage regimen to achieve similar therapeutic levels to those observed in other animal species. All these findings support the use of pig as an animal model to study the anti-inflammatory effects of CP in humans.

In vivo pharmacokinetic evaluation of carprofen delivery from intra-articular nanoparticles in rabbits: A population modelling approach

Osteoarthritis is treated with COX or fosfolipase A2 inhibitors such as carprofen, a propionic acid NSAID. The enhancement of its action over the articular cartilage is mandatory to facilitate its therapeutic application. Drug uptake into the cartilage requires high synovial fluid concentrations, anticipating its rapid distribution towards bloodstream. Thus, intraarticular administration improves local targeting of the drug, lining with the site of action. A pharmacokinetic study in rabbits has been performed to evaluate carprofen nanoparticles after intraarticular administration. Pharmacokinetic analysis of plasma profiles through a modelling approach, has demonstrated the rapid distribution of drug outside of synovial chamber but mainly remaining in plasma. The data modelling has demonstrated the existence of two release-absorption processes when the nanoparticles are administered in the synovial space. Additionally, results are predictive of the PK profile of some other species such as cat, dogs or humans.

Pharmacokinetics of carprofen and firocoxib for medication control in racing greyhounds

Animals used in sport should be treated as required to ensure animal welfare but any such use of medication should also be controlled to ensure integrity. Pharmacokinetic studies on groups of six greyhounds were performed to measure plasma and urine levels of carprofen and firocoxib to inform medication control advice. Using the standard methodology for medication control the Irrelevant Plasma Concentration was determined as 20 and 2 ng/mL for carprofen and firocoxib, respectively. The Irrelevant Urine Concentration was also determined as 0.3 and 2 ng/mL for carprofen and firocoxib, respectively. These Irrelevant Plasma and Urine Concentrations will allow laboratory Screening Limits, Detection Times and Withdrawal Time advice to be determined and publicised by regulators of greyhound racing. The Screening Limits will also inform Recommended Limits of Detection if meat-containing residues of these medications are fed to greyhounds.

Comparison of the effects on lameness of orally administered acetaminophen-codeine and carprofen in dogs with experimentally induced synovitis

OBJECTIVE

To compare the ability of acetaminophen-codeine (AC; 15.5 to 18.5 mg/kg and 1.6 to 2.0 mg/kg, respectively) or carprofen (4.2 to 4.5 mg/kg) administered PO to attenuate experimentally induced lameness in dogs.

ANIMALS

7 purpose-bred dogs.

PROCEDURES

A blinded crossover study was performed. Dogs were randomly assigned to receive AC or carprofen treatment first and then the alternate treatment a minimum of 21 days later. Synovitis was induced in 1 stifle joint during each treatment by intra-articular injection of sodium urate (SU). Ground reaction forces were assessed, and clinical lameness was scored at baseline (before lameness induction) and 3, 6, 9, 12, 24, 36, and 48 hours after SU injection. Plasma concentrations of acetaminophen, carprofen, codeine, and morphine were measured at various points. Data were compared between and within treatments by repeated-measures ANOVA.

RESULTS

During AC treatment, dogs had significantly higher lameness scores than during carprofen treatment at 3, 6, and 9 hours after SU injection. Peak vertical force and vertical impulse during AC treatment were significantly lower than values during carprofen treatment at 3, 6, and 9 hours. Plasma concentrations of carprofen (R)- and (S)-enantiomers ranged from 2.5 to 19.2 μg/mL and 4.6 to 25.0 μg/mL, respectively, over a 24-hour period. Plasma acetaminophen concentrations ranged from 0.14 to 4.6 μg/mL and codeine concentrations from 7.0 to 26.8 ng/mL, whereas plasma morphine concentrations ranged from 4.0 to 58.6 ng/mL.

CONCLUSIONS AND CLINICAL RELEVANCE

Carprofen as administered was more effective than AC at attenuating SU-induced lameness in dogs.

Influence of orthopedic examination on lameness scores and interobserver and intraobserver agreement in dogs with naturally occurring elbow osteoarthritis

OBJECTIVE

To determine the influence of orthopedic examination on numerical rating score (NRS) and visual analog score (VAS) when scoring lameness in dogs with elbow osteoarthritis (OA) and to evaluate interobserver and intraobserver agreement in NRS and VAS on the basis of video-graphic gait analysis.

DESIGN

Prospective blinded study.

ANIMALS

Eighteen client-owned dogs with radiographically confirmed elbow OA.

METHODS

Videos were obtained for all dogs at a walk and at a trot both prior to and immediately after orthopedic examination. All videos were randomly sequenced. Six observers, unaware of the timing of the video, independently assigned both NRS and VAS twice, with at least a 2-week interval. Scores were evaluated with mixed analysis of variance, and the agreement among observers was accessed by intraclass correlation coefficient (ICC).

RESULTS

No difference was detected between NRS and VAS at walk or at trot before and after orthopedic examination. Numeric rating score and VAS at walk were lower than those at trot before an orthopedic examination by scores of 0.17 (P = .0018) and 3.54 (P = .0019), respectively. The ICC for both scores for all observers was >0.9.

CONCLUSION

An orthopedic examination did not exacerbate the NRS and the VAS for dogs with elbow OA. Interobserver and intraobserver agreement was high for both lameness scores.

CLINICAL SIGNIFICANCE

Lameness may be scored after gait evaluation in dogs with elbow OA irrespective of the timing of a comprehensive orthopedic examination.

Anti-Inflammatory Effect of Carprofen Is Enhanced by Avocado/Soybean Unsaponifiables, Glucosamine and Chondroitin Sulfate Combination in Chondrocyte Microcarrier Spinner Culture

OBJECTIVE

Osteoarthritis is a painful, chronic joint disease affecting man and animals with no known curative therapies. Palliative nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used but they cause adverse side effects prompting the search for safer alternatives. To address this need, we evaluated the anti-inflammatory activity of avocado/soybean unsaponifiables (ASU), glucosamine (GLU), and chondroitin sulfate (CS) with or without the NSAID carprofen.

DESIGN

Canine chondrocytes were propagated in microcarrier spinner culture and incubated with (1) control medium, (2) ASU (8.3 µg/mL) + GLU (11 µg/mL) + CS (20 µg/mL) combination for 24 hours; and/or carprofen (40 ng/mL). Cultures were next incubated with control medium alone or IL-1β (10 ng/mL) for another 24 hours. Production of PGE2, IL-6, IL-8, and MCP-1 (also known as CCL-2) were measured by ELISA.

RESULTS

Chondrocytes proliferated in microcarrier spinner culture and produced type II collagen and aggrecan. Stimulation with IL-1β induced significant increases in PGE2, IL-6, IL-8, and MCP-1 production. The increases in production were suppressed by carprofen as well as [ASU+GLU+CS]. The combination of carprofen and [ASU+GLU+CS] reduced PGE2 production significantly more than either preparation alone. The inhibitory effect of carprofen on IL-6, IL-8, and MCP-1 production was significantly less than that of [ASU+GLU+CS], whereas the combination did not reduce the production of these molecules significantly more than [ASU+GLU+CS] alone.

CONCLUSIONS

The potentiating effect of [ASU+GLU+CS] on low-dose carprofen was identified in chondrocyte microcarrier spinner cultures. Our results suggest that the combination of low-dose NSAIDs like carprofen with [ASU+GLU+CS] could offer a safe, effective management for joint pain.

A complete cross-over design evaluating canine acceptance of Carprieve® and Rimadyl® carprofen chewable tablets in healthy dogs

Background

Osteoarthritis (OA) affects nearly 20% of all dogs greater than one year of age. Clinical signs include pain, discomfort, lameness, and ultimately lead to disability. Although there is currently no known cure, there are many therapeutic options that can slow the progression and alleviate the associated signs. There is ample supportive evidence demonstrating the efficaciousness of carprofen, a non-steroidal anti-inflammatory drug, in managing signs of OA. Since the approval of the pioneer product (Rimadyl®, Zoetis; Kalamazoo, Michigan), the United States Food and Drug Administration (FDA) has assented to several other generic, bioequivalent products. The objective of this 2 × 2 complete cross-over design was to assess the acceptance of two bioequivalent carprofen liver-flavored chewable tablets (containing 25 mg carprofen), Rimadyl® and Carprieve® (Norbrook Laboratories Limited; Newry, Northern Ireland) in 37 healthy purpose-bred dogs.

Results

Overall, 73.0% (27/37) and 70.3% (26/37) of dogs voluntarily accepted Rimadyl® and Carprieve®, respectively. Considering acceptability tests paired by individual dog, 64.9% of dogs (n = 24) voluntarily accepted both Rimadyl® and Carprieve® chewable tablets whereas 21.6% (8) of dogs denied or partially accepted both products offered. Three dogs (8.1%) fully accepted Rimadyl® but did not accept Carprieve®. Conversely, two dogs (5.4%) fully accepted Carprieve® but did not accept Rimadyl®. Canine acceptability did not significantly differ between Carprieve® and Rimadyl® carprofen chewable tablets (P = 0.65).

Conclusions

Utilizing a 2 × 2 complete cross-over design, this study provides evidence that canine acceptability of a single-dose did not differ between Carprieve® and Rimadyl® chewable tablets.

Avaliação psicométrica em português do indicador de dor crônica de Helsinki em cães com sinais crônicos de osteoartrite

RESUMO Objetivou-se determinar a validade, a confiabilidade e a sensibilidade do indicador de dor crônica de Helsinki (IDCH) em português, além de estabelecer correlação entre a plataforma de pressão em cães com displasia coxofemoral (DCF). O questionário foi preenchido por tutores de 40 animais com DCF e por 16 tutores de cães saudáveis. Os animais com DCF foram tratados com carprofeno 4,4mg/kg (GT= 21) ou placebo (GP= 19), administrados uma vez ao dia, durante quatro semanas. A avaliação consistiu no preenchimento do questionário (IDCH), na escala analógica visual de dor (EAVdor) e na escala analógica visual de locomoção (EAVloc) com duas semanas (A1) e imediatamente antes do tratamento (A2), duas (S2) e quatro (S4) semanas de tratamento e após duas semanas do término do tratamento (S6). A consistência interna dos dados foi considerada excelente (alfa de Cronbach = 0,89). Houve correlação moderada entre o IDCH e a EAVdor e boa entre o IDCH e a EAVloc, porém não houve diferença entre o grupo tratado com carprofeno e placebo no IDCH. Não houve correlação entre os dados da plataforma de pressão e o IDCH. O questionário apresentou validade de constructo, critério e fidedignidade e pode-se empregá-lo em países de língua portuguesa em cães com osteoartrite.

Agmatine for Pain Management in Dogs With Coxofemoral Joint Osteoarthritis: A Pilot Study

Background: Pain from coxofemoral joint (CFJ) osteoarthritis (OA) characteristic of canine hip dysplasia (CHD) afflicts many dogs. Intervertebral disc (IVD) degeneration is a common CFJ OA comorbidity. Non-steroidal anti-inflammatory drug (NSAID) administration is standard for treatment of pain from degenerative joint disease. Potential side effects and tolerance from prolonged administration drive efforts to identify compounds that may be alternatives to or combined with NSAIDs. Agmatine, decarboxylated arginine, reportedly alleviates neuropathic pain, a likely component of OA pain. The objective of this study was to compare treatment response to agmatine and carprofen in dogs with varying degrees of CFJ OA with or without IVD degeneration and to test the hypothesis that agmatine improves hindlimb use comparably to carprofen and more than placebo.

Methods: Nine hound-type dogs received oral carprofen (4.4 mg/kg, sid) for 7 days. Six months later, oral agmatine sulfate (25 mg/kg, bid) or placebo (hydroxypropyl methylcellulose, bid) was administered to the same dogs for 28 days with a 2 week washout period between treatments. Validated pain assessment scores were measured before treatment and every seven days throughout the treatment periods. Serum chemistry levels and ground reaction forces (GRF) were quantified before and after each treatment period. A board-certified radiologist quantified radiographic CFJ OA based on Orthopedic Foundation for Animals criteria and IVD degeneration on magnetic resonance images. GRFs were compared among treatments at each time point and among time points for each treatment.

Results: There were no detectable adverse effects with any treatment. Significant results included improved GRFs in dogs with mild CFJ OA (N = 3) following agmatine administration compared to carprofen or placebo and a trend for improved GRFs in dogs with moderate CFJ OA (N = 2) following carprofen vs. agmatine or placebo. Neither agmatine nor carprofen improved GRFs in dogs with severe CFJ OA (N = 4). The GRFs improved in dogs with IVD degeneration (N = 3) following carprofen treatment compared to agmatine or placebo regardless of CFJ OA score, but no effect was observed in dogs with normal lumbar spines (N = 6).

Conclusions: Results support agmatine over carprofen treatment to improve limb use in dogs with early or mild CFJ OA, while carprofen may be the better choice for dogs with moderate CFJ OA or IVD degeneration regardless of CFJ OA severity.

A study of the pharmacokinetics and thromboxane inhibitory activity of a single intramuscular dose of carprofen as a means to establish its potential use as an analgesic drug in white rhinoceros

The alleviation of pain and prevention of suffering are key aspects of animal welfare. Unfortunately, analgesic drugs are not available for all species. White rhinoceros (Ceratotherium simum), representing one of such species, which survive poaching attempts inflicted with severe facial injuries and gunshot wounds, nonetheless require analgesic support. To improve treatment conditions, this study explored the use of carprofen for the treatment of pain and inflammation in white rhinoceros. The pharmacokinetics of 1 mg/kg intramuscular carprofen was evaluated in six healthy white rhinoceros. The half-life of λ_z and mean residence time was 105.71 ± 15.67 and 155.01 ± 22.46 hr, respectively. The area under the curve and the maximum carprofen concentration were 904.61 ± 110.78 μg ml^-1  hr^-1 and 5.77 ± 0.63 μg/ml, respectively. Plasma TXB₂ inhibition demonstrated anti-inflammatory properties and indicated that carprofen may be effective for a minimum of 48 hr in most animals. With its long half-life further indicating that a single dose could be effective for several days, we suggest that carprofen may be a useful drug for the treatment of white rhinoceros.

Therapeutic response analysis in dogs with naturally occurring osteoarthritis

OBJECTIVE

Reporting the rate of positive (+) and negative (-) responders based on an objective outcome measure of pain-related functional disability/lameness in dogs with naturally occurring osteoarthritis (OA), and the relationship between initial lameness severity and the odds of being a (+) responder.

STUDY DESIGN

Retrospective analysis of published peer-reviewed clinical trials in dogs with naturally occurring OA.

ANIMALS

Dogs (n = 213) with hip and/or stifle afflicted-joints.

METHODS

A responder analysis was undertaken using a previously determined cut-off value of ±2.0% of body weight using the peak of vertical force (PVF). Among the selected trials, PVF was acquired under similar conditions. Therapeutic approaches were therapeutic diets, natural health products and nonsteroidal anti-inflammatory drugs.

RESULTS

Among dogs receiving a therapeutic approach as described above (n = 121), 62.8% [95% confidence interval, 53.9-70.9] were defined as (+) responders, whereas 11.6% [7.0-18.5] were (-) responders, accounting for a net (+) response rate by 51.2% [42.0-60.4]. In dogs receiving a negative control (n = 92), the net (+) response rate was 1.1% [0.0-5.9]. The number needed to treat was 4, and the effect size 0.7 [0.4-1.0]. The odds ratio of being a (+) responder under the therapeutic approaches was 2.85 [1.57-5.17] (p < 0.001). For every less severe lameness manifested with an increment in PVF by 1% body weight, the chance of being a (+) responder following treatment decreased by 9% (odds ratio 0.91 [0.86-0.97], p = 0.006).

CONCLUSION AND CLINICAL RELEVANCE

The rate of (+) responder optimizes decision making for the management of pain-related clinical signs of OA. Evidence-based medicine was further supported by clinical metrics based on an objective outcome measure of pain-related functional disability/lameness. This study also revealed that dogs with a mild lameness are less prone to be improved, emphasizing the need to carefully manage OA dogs in spite of a more subtle affliction.

Modifications of gait as predictors of natural osteoarthritis progression in STR/Ort mice

Objective

Osteoarthritis (OA) is a common chronic disease for which disease-modifying therapies are not currently available. Studies to seek new targets for slowing the progress of OA rely on mouse models, but these do not allow for longitudinal monitoring of disease development. This study was undertaken to determine whether gait can be used to measure disease severity in the STR/Ort mouse model of spontaneous OA and whether gait changes are related to OA joint pain.

Methods

Gait was monitored using a treadmill-based video system. Correlations between OA severity and gait at 3 treadmill speeds were assessed in STR/Ort mice. Gait and pain behaviors of STR/Ort mice and control CBA mice were analyzed longitudinally, with monthly assessments.

Results

The best speed to identify paw area changes associated with OA severity in STR/Ort mice was found to be 17 cm · seconds⁻¹. Paw area was modified with age in CBA and STR/Ort mice, but this began earlier in STR/Ort mice and correlated with the onset of OA at 20 weeks of age. In addition, task noncompliance appeared at 20 weeks. Surprisingly, STR/Ort mice did not show any signs of pain with OA development, even when treated with the opioid antagonist naloxone, but did exhibit normal pain behaviors in response to complete Freund's adjuvant–induced arthritis.

Conclusion

The present results identify an animal model in which OA severity and OA pain can be studied in isolation from one another. The findings suggest that paw area and treadmill noncompliance may be useful tools to longitudinally monitor nonpainful OA development in STR/Ort mice. This will help in providing a noninvasive means of assessing new therapies to slow the progression of OA.

Mavacoxib and meloxicam for canine osteoarthritis: a randomised clinical comparator trial

NSAIDs are the cornerstone of medical management of canine osteoarthritis (OA). Meloxicam is a daily-administered NSAID widely available in a liquid formulation and manufacturer's summary of product characteristics (SPC) advise that it is given at the lowest effective dose. Mavacoxib is a long-acting NSAID given as a monthly tablet. This study compares these drugs in the management of canine OA. In all, 111 dogs with OA of the elbow, hip or stifle were randomly assigned to receive one of these NSAIDs for a 12-week period, and to administer them as per the manufacturer's SPC. Outcomes, including ground reaction forces and three validated clinical metrology instruments, were measured at baseline, 6 and 12 weeks. Improvements were seen in all outcome measures for both groups to a similar degree, and adverse events occurred at a similar rate. There were significant improvements in outcome measures from week 6 to week 12, as well as from baseline. Long-term meloxicam dose was more important than recent dose. Clinical efficacy and adverse event rates are similar for meloxicam and mavacoxib when administered as per their UK SPC. This is relevant information for veterinary surgeons when prescribing NSAID treatment for canine OA.

The Canine Orthopedic Index. Step 1: Devising the items

OBJECTIVE

To develop questions for an owner-completed outcome assessment instrument for dogs with orthopedic disease.

STUDY DESIGN

Focus groups, key-informant interviews, surveys.

SAMPLE POPULATION

Owners of dogs with osteoarthritis (OA).

METHODS

Audio recorded focus groups were transcribed. Descriptive statistics around discussed topics were calculated. A list of frequently discussed behaviors underwent discrimination and frequency endorsement analysis and was circulated for refinement among veterinarians experienced in treating dogs with orthopedic disease. The final list of behaviors was transformed into a series of questions and organized as the preliminary instrument for testing in further studies.

RESULTS

Owners (n = 27) participated in 4 focus groups. Based on the frequency of comments generated during focus groups and key-informant interviews, 30 behaviors were further screened by discrimination analysis and endorsement frequency in an additional cohort of 60 owners. No behaviors were classified as "good" for discriminating between front and hind limb disease so a single, non-limb-specific instrument was developed. Four behaviors had an endorsement frequency ≤ 33% and were not considered further for inclusion in the preliminary instrument. Twenty-one questions associated with the remaining behaviors were used to create the preliminary Canine Orthopedic Index (COI) for psychometric testing in further studies.

CONCLUSIONS

A 21-question owner-completed COI was successfully developed in preparation for psychometric testing studies.

Systematic review of nonsteroidal anti-inflammatory drug-induced adverse effects in dogs

The aim of this systematic review was to identify, assess, and critically evaluate the quality of evidence of nonsteroidal anti-inflammatory drug (NSAID)-induced adverse effects in dogs. Original prospective studies published in peer-reviewed journals in English (1990-2012) that reported data on the safety of NSAIDs administration in dogs were searched. For each study, design type (I, II, III, or IV) and assessment of quality (+, Ø, -) were rated. For each drug, quantity and consistency rating (***, **, *) and strength of evidence (high, moderate, low, or extremely low) were identified and evaluated. The strength of evidence was defined in terms of how applicable and relevant the conclusions were to the target population. Sixty-four studies met the inclusion criteria. Thirty-five (55%) research studies and 29 (45%) clinical trials were identified. A high strength of evidence existed for carprofen, firocoxib, and meloxicam; moderate for deracoxib, ketoprofen, and robenacoxib; and low for etodolac. Quality and consistency rating were as follows: carprofen (***/***), deracoxib (**/***), etodolac (*/unable to rate), firocoxib (***/**), ketoprofen (**/***), meloxicam (***/***), and robenacoxib (**/**), respectively. Adverse effects were detected in 35 studies (55%) and commonly included vomiting, diarrhea, and anorexia. Three studies (5%) reported a power analysis related to adverse effects of ≥80%. In randomized, placebo-controlled, blinded studies (n = 25, 39%), the incidence of adverse effects was not statistically different between treated and control dogs. Finally, most studies were not appropriately designed to determine the safety of NSAIDs, and involved a healthy nongeriatric population of research dogs.

Validation of orthopedic postoperative pain assessment methods for dogs: a prospective, blinded, randomized, placebo-controlled study

In the context of translational research, there is growing interest in studying surgical orthopedic pain management approaches that are common to humans and dogs. The validity of postoperative pain assessment methods is uncertain with regards to responsiveness and the potential interference of analgesia. The hypothesis was that video analysis (as a reference), electrodermal activity, and two subjective pain scales (VAS and 4A-VET) would detect different levels of pain intensity in dogs after a standardized trochleoplasty procedure. In this prospective, blinded, randomized study, postoperative pain was assessed in 25 healthy dogs during a 48-hour time frame (T). Pain was managed with placebo (Group 1, n = 10), preemptive and multimodal analgesia (Group 2, n = 5), or preemptive analgesia consisting in oral tramadol (Group 3, n = 10). Changes over time among groups were analyzed using generalized estimating equations. Multivariate regression tested the significance of relationships between pain scales and video analysis. Video analysis identified that one orthopedic behavior, namely ‘Walking with full weight bearing’ of the operated leg, decreased more in Group 1 at T24 (indicative of pain), whereas three behaviors indicative of sedation decreased in Group 2 at T24 (all p<0.004). Electrodermal activity was higher in Group 1 than in Groups 2 and 3 until T1 (p<0.0003). The VAS was not responsive. 4A-VET showed divergent results as its orthopedic component (4A-VETleg) detected lower pain in Group 2 until T12 (p<0.0009), but its interactive component (4A-VETbeh) was increased in Group 2 from T12 to T48 (p<0.001). Concurrent validity established that 4A-VETleg scores the painful orthopedic condition accurately and that pain assessment through 4A-VETbeh and VAS was severely biased by the sedative side-effect of the analgesics. Finally, the video analysis offered a concise template for assessment in dogs with acute orthopedic pain. However, subjective pain quantification methods and electrodermal activity need further investigation.

Use of an activity monitor to detect response to treatment in dogs with osteoarthritis

OBJECTIVE

To determine whether an activity monitor (AM) could be used to detect changes in activity in dogs with osteoarthritis treated with carprofen or a placebo.

DESIGN

Randomized controlled trial.

ANIMALS

70 dogs with no clinically important abnormalities other than osteoarthritis for which they were not currently being treated.

PROCEDURES

Dogs wore an AM continuously for 21 days. On days 8 through 21, the dogs were treated with carprofen (n = 35) or a placebo (35). Total activity counts for days 1 through 7 (baseline) were compared with total activity counts for days 15 through 21 (endpoint). The change in total activity count from baseline to endpoint was assessed within each treatment group as well as between groups. Linear regression analysis was performed to test for an association between treatment and percentage change in activity counts while controlling for other variables.

RESULTS

For placebo-treated dogs, median baseline total activity count was not significantly different from median endpoint total activity count (1,378,408 vs 1,310,112, respectively). For dogs receiving carprofen, there was a significant increase in median activity count from baseline to endpoint (1,276,427 vs 1,374,133). When age and baseline activity counts were controlled for, dogs in the carpofen-treated group had a 20% increase in activity counts, compared with placebo-treated dogs (95% confidence interval, 10% to 26%).

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that the AM used in the present study may be a valid outcome assessment tool for documenting improved activity associated with treatment in dogs with osteoarthritis.

Review of the safety and efficacy of long-term NSAID use in the treatment of canine osteoarthritis

The published, peer-reviewed literature was systematically searched for information on the safety and efficacy of long-term (defined as 28 days or more of continuous therapy) NSAID use in the treatment of canine osteoarthritis. Online databases were reviewed in June 2008 and papers were selected based on their relevance. Fifteen papers were identified and evaluated. Six of seven papers indicated a benefit of long-term treatment over short-term treatment in terms of the reduction of clinical signs or lameness; one study showed no benefit. Fourteen papers evaluated safety with calculated experimental (adverse) event rates (EER) between 0 and 0.31, but there was no correlation between study length and EER (rs=-0.109, P=0.793). The balance of evidence for the efficacy of NSAIDs supports longer-term use of these agents for increased clinical effect. There is no indication in the literature that such an approach is associated with a reduction in safety, although robust data on the safety of long-term NSAID use are lacking in large numbers of dogs.

Systematic review of the management of canine osteoarthritis

This review assesses the evidence for the efficacy of therapies used in the management of osteoarthritis in dogs on the basis of papers published in peer-reviewed journals in English between 1985 and July 2007. Sixty-eight papers were identified and evaluated. They considered four alternative therapies, one use of functional food, two intra-articular agents, six nutraceutical agents, 21 pharmacological agents, two physical therapies, three surgical techniques and two combinations of weight control. There was a high level of comfort (strong evidence) for the efficacy of carprofen, firocoxib and meloxicam, and a moderate level of comfort for the efficacy of etodolac in modifying the signs of osteoarthritis. There was a moderate level of comfort for the efficacy of glycosaminoglycan polysulphate, licofelone, elk velvet antler and a functional food containing green-lipped mussel for the modification of the structures involved in the disease. There was weak or no evidence in support of the use of doxycycline, electrostimulated acupuncture, extracorporeal shockwave therapy, gold wire acupuncture, hyaluronan, pentosan polysulphate, P54FP (extract of turmeric), tiaprofenic acid or tibial plateau levelling osteotomy.

Ability of the canine brief pain inventory to detect response to treatment in dogs with osteoarthritis

OBJECTIVE

To determine whether the Canine Brief Pain Inventory (CBPI) can detect changes in dogs with osteoarthritis treated with an NSAID or a placebo.

DESIGN

Double-blind, randomized, placebo-controlled clinical trial.

ANIMALS

70 dogs with osteoarthritis.

PROCEDURES

Owners completed the CBPI on day 0. Dogs received carprofen or a placebo on days 1 through 14. Owners completed the CBPI again on day 14. Pain severity and pain interference scores from the CBPI were calculated, and the change from day 0 to day 14 was assessed within each group and between groups.

RESULTS

No significant differences were detected in median scores for pain severity (3.50 and 3.25 on days 0 and 14, respectively) and pain interference (3.92 and 3.25 on days 0 and 14, respectively) in dogs receiving the placebo. Dogs receiving carprofen had significant changes in median scores for pain severity (4.25 to 2.25 on days 0 and 14, respectively) and pain interference (4.33 to 2.67 on days 0 and 14, respectively).There was a significantly greater improvement in pain severity and pain interference scores in dogs treated with carprofen, compared with improvement in scores for dogs receiving the placebo.

CONCLUSIONS AND CLINICAL RELEVANCE

The CBPI was able to detect improvements in pain scores in dogs with osteoarthritis treated with an NSAID or a placebo. These results, in combination with previous reliability and validity testing, support the use of the CBPI to obtain quantifiable assessments from owners regarding the severity and impact of chronic pain and treatment for dogs with osteoarthritis.

Comparison of the effects of firocoxib, carprofen and vedaprofen in a sodium urate crystal induced synovitis model of arthritis in dogs

A randomized, placebo-controlled, four-period cross-over laboratory study involving eight dogs was conducted to confirm the effective analgesic dose of firocoxib, a selective COX-2 inhibitor, in a synovitis model of arthritis. Firocoxib was compared to vedaprofen and carprofen, and the effect, defined as a change in weight bearing measured via peak ground reaction, was evaluated at treatment dose levels. A lameness score on a five point scale was also assigned to the affected limb. Peak vertical ground reaction force was considered to be the most relevant measurement in this study. The firocoxib treatment group performed significantly better than placebo at the 3 h post-treatment time point and significantly better than placebo and carprofen at the 7 h post-treatment time point. Improvement in lameness score was also significantly better in the dogs treated with firocoxib than placebo and carprofen at both the 3 and 7 h post-treatment time points.

Development and psychometric testing of an instrument designed to measure chronic pain in dogs with osteoarthritis

OBJECTIVE

To develop and psychometrically test an owner self-administered questionnaire designed to assess severity and impact of chronic pain in dogs with osteoarthritis.

SAMPLE POPULATION

70 owners of dogs with osteoarthritis and 50 owners of clinically normal dogs.

PROCEDURES

Standard methods for the stepwise development and testing of instruments designed to assess subjective states were used. Items were generated through focus groups and an expert panel. Items were tested for readability and ambiguity, and poorly performing items were removed. The reduced set of items was subjected to factor analysis, reliability testing, and validity testing.

RESULTS

Severity of pain and interference with function were 2 factors identified and named on the basis of the items contained in them. Cronbach's alpha was 0.93 and 0.89, respectively, suggesting that the items in each factor could be assessed as a group to compute factor scores (ie, severity score and interference score). The test-retest analysis revealed kappa values of 0.75 for the severity score and 0.81 for the interference score. Scores correlated moderately well (r = 0.51 and 0.50, respectively) with the overall quality-of-life (QOL) question, such that as severity and interference scores increased, QOL decreased. Clinically normal dogs had significantly lower severity and interference scores than dogs with osteoarthritis.

CONCLUSIONS AND CLINICAL RELEVANCE

A psychometrically sound instrument was developed. Responsiveness testing must be conducted to determine whether the questionnaire will be useful in reliably obtaining quantifiable assessments from owners regarding the severity and impact of chronic pain and its treatment on dogs with osteoarthritis.

Nonsteroidal antiinflammatory drugs: a review

The increasing use of nonsteroidal antiinflammatory drugs (NSAIDs) in small animals has resulted in the development of new and innovative additions to this class of drugs. Examples of NSAIDs now available for use in small animals include aspirin, etodolac, carprofen, ketoprofen, meloxicam, deracoxib, and tepoxalin. The purposes of this article are to review the pathophysiology of prostaglandin synthesis and inhibition, the mechanisms of action, pharmacokinetics, pharmacological effects, and potential adverse reactions of aspirin and the newly released NSAIDs.

Evaluation of Agreement Between Numerical Rating Scales, Visual Analogue Scoring Scales, and Force Plate Gait Analysis in Dogs

OBJECTIVE

To evaluate the accuracy of numerical rating (NRS) and visual analogue (VAS) scoring scales compared with force plate gait analysis and agreement between observers for each scoring scale.

STUDY DESIGN

Experimental study.

ANIMALS

Mixed breed dogs (n=21) with a right limb tibial osteotomy repaired with an external fixator.

METHODS

Three small-animal veterinarians with orthopedic training scored lameness using NRS and VAS before surgery, and at 4 and 8 weeks after surgery. Peak force and impulse were determined at the same time points using a force plate. Agreement between observers and with force plate data was assessed. Significance was set at P< or =.05.

RESULTS

Agreement was generally low among observers for both NRS and VAS scores. When evaluated at each time point, an acceptable level of agreement was present only at 4 weeks after surgery. Only impulse had a significant relationship with some of the observers' subjective scores. No significant relationships between any observer's scores and force plate data existed if very lame dogs were omitted.

CONCLUSIONS

Subjective scoring scales do not replace force plate gait analysis. Agreement is low unless lameness is severe, and each observer uses an individually unique scale. Subjective scoring scales most accurately reflect force plate gait analysis when lameness is severe.

CLINICAL RELEVANCE

Subjective lameness scoring scales may not accurately reflect lameness and do not replace force plate gait analysis. Observers must stay the same during the duration of a study for accurate analyses.

Systematic review of clinical trials of treatments for osteoarthritis in dogs

OBJECTIVE

To identify and critically evaluate the quality of evidence of the most commonly used pharmacologic, nutraceutical, and purported slow-acting drugs of osteoarthritis for the management of osteoarthritis in dogs by use of the FDA's evidence-based medicine scoring system.

DESIGN

Systematic review.

SAMPLE POPULATION

16 clinical trials.

PROCEDURES

A broad bibliographic search was performed prior to May 2006. Inclusion criteria focused on prospective trials evaluating commonly used medical treatment interventions for the management of osteoarthritis in dogs and published in peer-reviewed journals. The analysis consisted of the following: study design rating, quality factor rating, quantity rating, consistency rating, relevance to disease risk reduction rating, and cumulative strength of evidence ranking.

RESULTS

4 trials evaluating meloxicam were rated as type I. Three trials evaluating carprofen were rated as type I, and 2 trials were rated as type III. One trial evaluating each of the following agents was rated as type 1: etodolac; P54FP; polysulfated glycosaminoglycan; and a combination of chondroitin sulfate, glucosamine hydrochloride, and manganese ascorbate. Two trials evaluating pentosan polysulphate and 2 trails evaluating green-lipped mussels were rated as type I. One trial evaluating hyaluronan was rated as type III.

CONCLUSIONS AND CLINICAL RELEVANCE

A high level of comfort exists for meloxicam that the claimed relationship is scientifically valid and that its use is clinically efficacious for the treatment of osteoarthritis in dogs. A moderate level of comfort exists for carprofen; etodolac; pentosan polysulphate; green-lipped mussels; P54FP; polysulfated glycosaminoglycans; and a combination of chondroitin sulfate, glucosamine hydrochloride, and manganese ascorbate. An extremely low level of comfort exists for hyaluronan.

Effect of short-term sequential administration of nonsteroidal anti-inflammatory drugs on the stomach and proximal portion of the duodenum in healthy dogs

OBJECTIVE

To evaluate effects of injection with a nonsteroidal anti-inflammatory drug (NSAID) followed by oral administration of an NSAID on the gastrointestinal tract (GIT) of healthy dogs.

ANIMALS

6 healthy Walker Hounds.

PROCEDURES

In a randomized, crossover design, dogs were administered 4 treatments consisting of an SC injection of an NSAID or control solution (day 0), followed by oral administration of an NSAID or inert substance for 4 days (days 1 through 4). Treatment regimens included carprofen (4 mg/kg) followed by inert substance; saline (0.9% NaCl) solution followed by deracoxib (4 mg/kg); carprofen (4 mg/kg) followed by carprofen (4 mg/kg); and carprofen (4 mg/kg) followed by deracoxib (4 mg/kg). Hematologic, serum biochemical, and fecal evaluations were conducted weekly, and clinical scores were obtained daily. Endoscopy of the GIT was performed before and on days 1, 2, and 5 for each treatment. Lesions were scored by use of a 6-point scale.

RESULTS

No significant differences existed for clinical data, clinicopathologic data, or lesion scores in the esophagus, cardia, or duodenum. For the gastric fundus, antrum, and lesser curvature, an effect of time was observed for all treatments, with lesions worsening from before to day 2 of treatments but improving by day 5.

CONCLUSIONS AND CLINICAL RELEVANCE

Sequential administration of NSAIDs in this experiment did not result in clinically important gastroduodenal ulcers. A larger study to investigate the effect of sequential administration of NSAIDs for longer durations and in dogs with signs of acute and chronic pain is essential to substantiate these findings.

Pharmaceutical and nutraceutical management of canine osteoarthritis: present and future perspectives

Osteoarthritis (OA) is one of the most common chronic musculoskeletal diseases and causes of lameness in the dogs. The osteoarthritic disease process involves the entire synovial joint, encompassing the synovium, cartilage and underlying bone. Joint failure results from an abnormal mechanical strain causing damage to normal tissue or failure of pathologically impaired articular cartilage and bone under the influence of normal physiological strain or a combination of both. In both cases, the end point is cartilage loss and joint impairment. Osteoarthritic chondrocytes show an altered phenotype characterised by an excess production of catabolic factors, including metalloproteinases and reactive oxygen species. These factors constitute potential therapeutic targets and some new drugs and nutraceuticals have been proposed to promote the return to homeostasis. Until now, the therapeutic management of OA in dogs has been dominated by nonsteroidal anti-inflammatory drugs, but some new compounds, including diacerhein, with potential structure-modifying effects, are already used to treat OA in humans and could be helpful to manage OA in the dog. In addition, novel nutraceuticals, such as avocado/soybean unsaponifiable substances, have shown symptomatic effects in knee OA in humans, and could offer an alternative to prevent OA progression. This paper provides an overview of recent discoveries in the pathophysiology and in the therapeutic management of osteoarthritis in dogs.

Pharmacodynamics and pharmacokinetics of nonsteroidal anti-inflammatory drugs in species of veterinary interest

This review summarises selected aspects of the pharmacokinetics (PK) and pharmacodynamics (PD) of nonsteroidal anti-inflammatory drugs (NSAIDs). It is not intended to be comprehensive, in that it covers neither minor species nor several important aspects of NSAID PD. The limited objective of the review is to summarise those aspects of NSAID PK and PD, which are important to an understanding of PK-PD integration and PK-PD modelling (the subject of the next review in this issue). The general features of NSAID PK are: usually good bioavailability from oral, intramuscular and subcutaneous administration routes (but with delayed absorption in horses and ruminants after oral dosing), a high degree of binding to plasma protein, low volumes of distribution, limited excretion of administered dose as parent drug in urine, marked inter-species differences in clearance and elimination half-life and ready penetration into and slow clearance from acute inflammatory exudate. The therapeutic effects of NSAIDs are exerted both locally (at peripheral inflammatory sites) and centrally. There is widespread acceptance that the principal mechanism of action (both PD and toxicodynamics) of NSAIDs at the molecular level comprises inhibition of cyclooxygenase (COX), an enzyme in the arachidonic acid cascade, which generates inflammatory mediators of the prostaglandin group. However, NSAIDs possess also many other actions at the molecular level. Two isoforms of COX have been identified. Inhibition of COX-1 is likely to account for most of the side-effects of NSAIDs (gastrointestinal irritation, renotoxicity and inhibition of blood clotting) but a minor contribution also to some of the therapeutic effects (analgesic and anti-inflammatory actions) cannot be excluded. Inhibition of COX-2 accounts for most and possibly all of the therapeutic effects of NSAIDs. Consequently, there has been an intensive search to identify and develop drugs with selectivity for inhibition of COX-2. Whole blood in vitro assays are used to investigate quantitatively the three key PD parameters (efficacy, potency and sensitivity) for NSAID inhibition of COX isoforms, providing data on COX-1:COX-2 inhibition ratios. Limited published data point to species differences in NSAID-induced COX inhibition, for both potency and potency ratios. Members of the 2-arylpropionate sub-groups of NSAIDs exist in two enantiomeric forms [R-(-) and S-(+)] and are licensed as racemic mixtures. For these drugs there are marked enantiomeric differences in PK and PD properties of individual drugs in a given species, as well as important species differences in both PK and PD properties.

Hepatocellular Toxicosis Associated with the Alternate Administration of Carprofen and Meloxicam in a Siberian Husky

A 4-year-old female Siberian Husky was diagnosed with pyogranulomatous steatitis at the site of a recurrence of left anal sac rupture (day 1). Carprofen and orbifloxacin were given for 13 days without improvement. A single dose of meloxicam was administered prior to surgical resection of the anal sac, and based on elevated liver enzyme activity, liver supportive therapy was initiated. The dog received carprofen and orbifloxacin orally on the evening of day 14. The dog became anorectic the following morning, and began vomiting. Despite supportive therapy, the dog was unresponsive to treatment and died on day 16. Postmortem examination revealed severe vacuolar change and acute necrosis of hepatocytes consistent with carprofen and meloxicam induced-toxicosis.

Pharmacology of drugs used to treat osteoarthritis in veterinary practice

As in humans, pain in animals may be associated with a wide range of conditions and circumstances, ranging from acute trauma to joint diseases. Joint diseases are common in companion animal medicine (horse, dog, cat) and at least 80% of cases are classified as osteoarthritis (OA). Several drug classes are available for OA therapy, including corticosteroids, non-steroidal antiinflammatory drugs (NSAIDs), agents with potential disease modifying properties and nutraceuticals. For long-term maintenance OA treatment, particularly in the horse and dog, NSAIDs are routinely and extensively used. This review outlines the pharmacokinetics (PK) and pharmacodynamics (PD) of NSAIDs in companion and farm animal species. NSAID PK and PD have been studied in models of acute inflammation, which enable use of PK-PD modeling to facilitate (a) studies of mechanism of action at the molecular level and (b) prediction of dosages for clinical use. The PK-PD approach is a powerful but underutilized tool which also facilitates inter-species comparisons.

Detection and identification of carprofen and its in vivo metabolites in greyhound urine by capillary gas chromatography-mass spectrometry

Rimadyl (carprofen) was administered orally to the racing greyhound at a dose of 2.2 mg kg(-1). Following both alkaline and enzymatic hydrolysis, postadministration urine samples were extracted by mixed mode solid-phase extraction (SPE) cartridges to identify target analyte(s) for forensic screening and confirmatory analysis methods. The acidic isolates were derivatised as trimethylsilyl ethers (TMS) and analysed by gas chromatography-mass spectrometry (GC-MS). Carprofen and five phase I metabolites were identified. Positive ion electron ionisation (EI(+)) mass spectra of the TMS derivatives of carprofen and its metabolites show a diagnostic base peak at M(+)*. -117 corresponding to the loss of COO-Si-(CH(3))(3) group as a radical. GC-MS with positive ion ammonia chemical ionisation (CI(+)) of the compounds provided both derivatised molecular mass and some structural information. Deutromethylation-TMS derivatisation was used to distinguish between aromatic and aliphatic oxidations of carprofen. The drug is rapidly absorbed, extensively metabolised and excreted as phase II conjugates in urine. Carprofen, three aromatic hydroxy and a minor N-hydroxy metabolite were detected for up to 48 h. For samples collected between 2 and 8 h after administration, the concentration of total carprofen ranged between 200 and 490 ng ml(-1). The major metabolite, alpha-hydroxycarprofen was detected for over 72 h and therefore can also be used as a marker for the forensic screening of carprofen in greyhound urine.

Pharmacodynamics and enantioselective pharmacokinetics of racemic carprofen in the horse

Carprofen is a nonsteroidal anti-inflammatory drug of the 2-arylpropionate subclass. It contains a single chiral centre and exists in two enantiomeric forms. In this study rac-carprofen, at two dosages, 0.7 and 4.0 mg/kg, and placebo were administered i.v. to six New Forest horses in a three period cross-over study. The concentration-time profiles were established for R(-) and S(+)-carprofen for plasma and both inflamed (exudate) and noninflamed (transudate) tissue cage fluids. R(-)-carprofen was the predominant enantiomer in all three fluids, as indicated by plasma area under the curve (AUC) values for R(-) and S(+)-carprofen of 117.4 and 22.6 microg h/mL (low dose carprofen) and 557.5 and 138.1 microg h/mL (high dose carprofen) respectively. Penetration of both enantiomers into exudate was slow and limited and passage into transudate was even lower. The pharmacodynamics of rac-carprofen was investigated at both the molecular level and in terms of the ability to suppress components of the tissue cage inflammatory response. Low dose carprofen produced only moderate and transient inhibition of serum thromboxane (Tx)B2 but failed to affect exudate prostaglandin (PG)E2 concentrations, whilst suppression of exudate leukotriene (LT)B4 and beta-glucuronidase was not significant. High dose carprofen produced greater and more persistent inhibition of serum TxB2 and virtually abolished exudate PGE2 synthesis. Some inhibition of LTB4 and beta-glucuronidase in exudate was also obtained. At both dosages rac-carprofen reduced the swelling produced by intradermal bradykinin injection but only high dose carprofen was anti-inflammatory as indicated by suppression of temperature rise over exudate tissue cages and neither dose affected leucocyte numbers in exudate. When considered in conjunction with previous data on carprofen, the present findings indicate that carprofen is not a selective inhibitor of cyclooxygenase (COX) isoenzymes, COX-1 and COX-2 in the horse, although it may show some preference for COX-2 inhibition. Because low dose carprofen, which is the clinically recommended dosage, produces minimal inhibition of COX, it is likely to achieve its therapeutic effects at least partially through other pathways, possibly including weak to moderate inhibition of 5-lipoxygenase and of enzyme release. The good safety margin of carprofen in clinical use might also be explained by weak COX inhibition and by other actions at the molecular level.