Differential inhibition of cyclooxygenase isoenzymes in the cat by the NSAID robenacoxib

Some Aspects and Convergence of Human and Veterinary Drug Repositioning

Drug innovation traditionally follows a de novo approach with new molecules through a complex preclinical and clinical pathway. In addition to this strategy, drug repositioning has also become an important complementary approach, which can be shorter, cheaper, and less risky. This review provides an overview of drug innovation in both human and veterinary medicine, with a focus on drug repositioning. The evolution of drug repositioning and the effectiveness of this approach are presented, including the growing role of data science and computational modeling methods in identifying drugs with potential for repositioning. Certain business aspects of drug innovation, especially the relevant factors of market exclusivity, are also discussed. Despite the promising potential of drug repositioning for innovation, it remains underutilized, especially in veterinary applications. To change this landscape for mutual benefits of human and veterinary drug innovation, further exploitation of the potency of drug repositioning is necessary through closer cooperation between all stakeholders, academia, industry, pharmaceutical authorities, and innovation policy makers, and the integration of human and veterinary repositioning into a unified innovation space. For this purpose, the establishment of the conceptually new "One Health Drug Repositioning Platform" is proposed. Oncology is one of the disease areas where this platform can significantly support the development of new drugs for human and dog (or other companion animals) anticancer therapies. As an example of the utilization of human and veterinary drugs for veterinary repositioning, the use of COX inhibitors to treat dog cancers is reviewed.

SINGLE-DOSE, MULTIPLE-DOSE, AND THERAPEUTIC DRUG MONITORING PHARMACOKINETICS OF FIROCOXIB IN ASIAN ELEPHANTS (ELEPHAS MAXIMUS)

Firocoxib is a COX-2-selective nonsteroidal anti-inflammatory drug (NSAID) with limited effects on COX-1, which means it likely has fewer side effects than typically associated with other NSAIDs. This study determined possible doses of firocoxib based on single- and multidose pharmacokinetic trials conducted in 10 Asian elephants (Elephas maximus). Initially, two single oral dose trials (0.01 and 0.1 mg/kg) of a commercially available tablet (n = 6) and paste (n = 4) formulation were used to determine a preferred dose. The 0.1 mg/kg dose was further evaluated via IV single dose (n = 3) and oral multidose trials (tablets n = 6; paste n = 4). Serum peak and trough firocoxib concentrations were also evaluated in Asian elephants (n = 4) that had been being treated for a minimum of 90 consecutive days. Key pharmacokinetic parameters for the 0.1 mg/kg single-dose trials included mean peak serum concentrations of 49 ± 3.3 ng/ml for tablets and 62 ± 14.8 ng/ml for paste, area under the curve (AUC) of 1,332 ± 878 h*mg/ml for tablets and 1,455 ± 634 h*mg/ml for paste, and half-life (T1/2) of 34.3 ± 30.3 h for tablets and 19.9 ± 12.8 h for paste. After 8 d of dosing at 0.1 mg/kg every 24 h, pharmacokinetic parameters stabilized to an AUC of 6,341 ± 3,003 h*mg/ml for tablets and 5,613 ± 2,262 for paste, and T1/2 of 84.4 ± 32.2 h for tablets and 62.9 ± 2.3 h for paste. Serum COX inhibition was evaluated in vitro and ex vivo in untreated elephant plasma, where firocoxib demonstrated preferential inhibition of COX-2. No adverse effects from firocoxib administration were identified in this study. Results suggest administering firocoxib to Asian elephants at a dose of 0.1 mg/kg orally, using either tablet or paste formulations, every 24 h.

Robenacoxib versus meloxicam following ovariohysterectomy in cats: A randomised, prospective clinical trial involving owner-based assessment of pain

BACKGROUND

Injectable non-steroidal anti-inflammatory drugs (NSAIDs) are commonly prescribed to queens undergoing ovariohysterectomy (OVH), but the requirement for postoperative administration is unclear and practices vary. Existing studies assessing efficacy rely on pain scoring by experienced clinicians. However, following OVH, most cats are discharged within hours of recovery.

METHODS

Cats undergoing OVH were randomly assigned to two treatment groups: MEL and ROB. Cats in the MEL group (n = 76) received meloxicam (0.2 mg/kg) and those in the ROB group (n = 65) received robenacoxib (2 mg/kg). Owners were contacted by a blinded assessor 3 days postoperatively and asked to identify physical or behavioural changes and to assign pain scores using a numerical rating scale.

RESULTS

More cats in the ROB group displayed abnormal behaviours than cats in the MEL group (p = 0.03). Most owners assigned a pain score of 0 (72%) (n = 101), but pain scores were significantly higher in the ROB group than in the MEL group (p = 0.005).

LIMITATION

Methods of owner assessment of pain in cats have not been validated.

CONCLUSIONS

Both meloxicam and robenacoxib are effective in controlling postoperative pain. Meloxicam may have improved efficacy in certain patient populations. Applying a blanket approach to prescribing NSAIDs to cats undergoing OVH postoperatively may not be necessary. This has safety, environmental and cost implications.

The impact of stress and anesthesia on animal models of infectious disease

Stress and general anesthesia have an impact on the functional response of the organism due to the detrimental effects on cardiovascular, immunological, and metabolic function, which could limit the organism's response to an infectious event. Animal studies have formed an essential step in understanding and mitigating infectious diseases, as the complexities of physiology and immunity cannot yet be replicated in vivo. Using animals in research continues to come under increasing societal scrutiny, and it is therefore crucial that the welfare of animals used in disease research is optimized to meet both societal expectations and improve scientific outcomes. Everyday management and procedures in animal studies are known to cause stress, which can not only cause poorer welfare outcomes, but also introduces variables in disease studies. Whilst general anesthesia is necessary at times to reduce stress and enhance animal welfare in disease research, evidence of physiological and immunological disruption caused by general anesthesia is increasing. To better understand and quantify the effects of stress and anesthesia on disease study and welfare outcomes, utilizing the most appropriate animal monitoring strategies is imperative. This article aims to analyze recent scientific evidence about the impact of stress and anesthesia as uncontrolled variables, as well as reviewing monitoring strategies and technologies in animal models during infectious diseases.

Pharmacology, safety, efficacy and clinical uses of the COX-2 inhibitor robenacoxib

Robenacoxib is a veterinary‐approved non‐steroidal anti‐inflammatory drug (NSAID) of the coxib group. It possesses anti‐hyperalgesic, anti‐inflammatory and anti‐pyretic properties. Robenacoxib inhibits the cyclooxygenase (COX)‐2 isoform of COX selectively (in vitro IC₅₀ ratios COX‐1:COX‐2, 129:1 in dogs, 32:1 in cats). At registered dosages (2 mg/kg subcutaneously in dogs and cats, 1–4 mg/kg orally in dogs and 1–2.4 mg/kg orally in cats), robenacoxib produces significant inhibition of COX‐2 whilst sparing COX‐1. The pharmacokinetic (PK) profile of robenacoxib is characterized by a high degree of binding to plasma proteins (>98%) and moderate volume of distribution (at steady state, 240 ml/kg in dogs and 190 ml/kg in cats). In consequence, the terminal half‐life in blood (<2 h) is short, despite moderate body clearance (0.81 L/kg/h) in dogs and low clearance (0.44 L/kg/h) in cats. Excretion is principally in the bile (65% in dogs and 72% in cats). Robenacoxib concentrates in inflamed tissues, and clinical efficacy is achieved with once‐daily dosing, despite the short blood terminal half‐life. In dogs, no relevant breed differences in robenacoxib PK have been detected. Robenacoxib has a wide safety margin; in healthy laboratory animals daily oral doses 20‐fold (dog, 1 month), eight‐fold (cat, 6 weeks) and five‐fold (dog, 6 months) higher than recommended clinical doses were well tolerated. Clinical efficacy and safety have been demonstrated in orthopaedic and soft tissue surgery, and in musculoskeletal disorders in dogs and cats.

Selective inhibition of cyclooxygenase-2 by enflicoxib, its enantiomers and its main metabolites in vitro in canine blood

Enflicoxib is approved for the treatment of pain and inflammation in canine osteoarthritis. The objective of this work was to assess the mechanistic basis of enflicoxib therapy investigating the COX inhibitory activity of enflicoxib (racemate), its enantiomers and its main metabolites using the canine whole blood assay. The (R)‐(+)‐Enflicoxib enantiomer and metabolite M8 (hydroxylated pyrazoline) did not induce significant COX inhibition. Enflicoxib and its (S)‐(‐)‐Enflicoxib enantiomer inhibited COX‐1 and COX‐2 with variable degree of preferential isoform inhibition, but no significant therapeutic effect is anticipated in vivo. The pyrazol metabolite showed the highest COX‐2 inhibition and was the most selective (IC₅₀ COX‐1/ COX‐2 ratio: 19.45). As the pyrazol metabolite shows saturable binding to red blood cells, its in vivo concentrations in plasma are lower than in whole blood. Accordingly, when applying the red blood cell partitioning, the respective IC₅₀ and IC₈₀ for COX‐2 inhibition decreased from 2.8 µM (1129 ng/ml) and 13.4 µM (5404 ng/ml) to 0.2 µM (80.7 ng/ml) and 1.2 µM (484 ng/ml) and the selectivity ratio increased to close to 55. The corrected pyrazol metabolite IC₅₀ and IC₈₀ are well within the plasma levels described in treated dogs.

Non-Linear Mixed-Effects Pharmacokinetic Modeling of the Novel COX-2 Selective Inhibitor Vitacoxib in Cats

The objective of this study was to develop a non-linear mixed-effects (NLME) model to describe the disposition kinetics of vitacoxib in cats following intravenous (I.V) and oral (P.O) (single and multiple) dosing. Data from six consecutive studies with 16 healthy neutered domestic short hair cats were pooled together to build a pharmacokinetic (PK) model using NLME. Population PK parameters were estimated using the stochastic approximation expectation maximization (SAEM) algorithm implemented in Monolix 2019R2. A two-compartment mammillary disposition model with simultaneous zero- and first-order absorption best described the PK of vitacoxib in plasma after oral dosing. The systemic CL of vitacoxib was found to be low (110 ml/h), with a steady-state volume of distribution (VSS) of 3.42 L in cats. Results from the automated covariate search in Monolix 2019R2 showed that bodyweight had a significant effect on the central volume of distribution of vitacoxib. Lastly, using Monte Carlo simulations, we investigated the time course of several dosages of vitacoxib from 0.01 to 8 mg/kg. Using this simulation set, we found a range of reasonable dosages that produce therapeutic plasma concentrations of vitacoxib for 24 h or more in cats.

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.

Six-month safety evaluation of robenacoxib tablets (Onsior™) in dogs after daily oral administrations

Background

Robenacoxib is a non-steroidal anti-inflammatory drug available for canine and feline use for the control of pain and inflammation marketed as Onsior™. The aim of this target animal safety study was to evaluate the 6-month safety profile of oral robenacoxib administration. It was a randomized, negative-controlled, parallel group study. Thirty-two healthy, young, experimentally naïve, purebred Beagle dogs were administered 0 (sham control, Group 1), 2, 6, and 10 mg/kg robenacoxib (corresponding to the upper end of the dosage range [1X, Group 2] and multiples thereof [3X and 5X, Group 3 and 4]), orally once daily for 6 months. Assessment of safety included general health and clinical observations, physical, neurological, ophthalmological and electrocardiographic examinations, gross and histopathological examinations and clinical pathology evaluations. Blood samples were collected for toxicokinetic assessment of robenacoxib.

Results

No serious adverse events were reported. When compared with control, no treatment effect was observed for body weight, feed or water consumption, clinical pathology, urinalysis and fecal examination parameters. There were no treatment-related changes in stifle joint tissues and microscopic/histopathology examinations of all tissues/organs were normal. Salivation and soft feces were noted in all groups but observed more frequently in the treated groups as compared with control. On Day 178, increased buccal mucosal bleeding times were observed in two treated animals (Group 3 and 4) and one dog in Group 4 displayed a retinal change. Decreased hopping and conscious proprioception was noted in four treated dogs. One dog in Group 2 had ventricular premature complexes. Post-mortem changes included mild, red foci on the cecum in one dog (Group 3) and minimal duodenal discoloration in one dog (Group 4), with no corresponding histological findings in either dog. Ovarian weights were decreased in females from Group 3 and 4 with no gross or histological changes in the ovaries. Blood concentrations of robenacoxib confirmed systemic exposure of treated dogs. Exposure increased with increasing doses and there were no accumulation of robenacoxib in blood.

Conclusions

Robenacoxib was well tolerated at doses from 2 to 10 mg/kg/day and this 6-month study supports the safe use of Onsior™ (robenacoxib) tablets in dogs for the intended dosing regimen.

Comparison of post-operative analgesic efficacy of tolfenamic acid and robenacoxib in ovariohysterectomized cats

The objective of this study was to evaluate the efficacy of a non-selective COX inhibitor (tolfenamic acid) and a selective COX-2 inhibitor (robenacoxib) for post-operative pain control in cats. Thirty cats undergoing ovariohysterectomy were randomly divided into three groups: the control (placebo) group, the tolfenamic acid (4 mg/kg/day) group, and the robenacoxib (1 mg/kg/day) group. Non-steroidal anti-inflammatory drugs (NSAIDs) were administered orally 2 hr before anesthesia induction and 24 and 48 hr post-operation. Buccal mucosal bleeding times (BMBTs) were assessed prior to anesthesia induction. Colorado pain scores and composite pain scores were evaluated in a blinded fashion before induction and 2, 8, 24, 30 and 48 hr post-operation. The Colorado pain scores of cats receiving robenacoxib were significantly lower than those of cats in the control group at 30 (P=0.0126) and 48 (P=0.0439) hr post-operation. The composite pain scores of cats from the robenacoxib group were lower than those of cats in the control group at 30 (P=0.0299) and 48 (P=0.0103) hr post-operation. The Colorado pain scores of cats receiving tolfenamic acid were significantly lower than those of cats in the control group at 30 hr (P=0.0186) post-operation. The composite pain scores in cats in the tolfenamic acid group were lower than the scores of cats in the control group at 24 (P=0.0403) and 48 (P=0.0413) hr post-operation. BMBTs remained within normal limits in all groups. Both tolfenamic acid and robenacoxib are useful for post-operative pain control in cats.

Effect of oral administration of robenacoxib on inhibition of paracentesis-induced blood-aqueous barrier breakdown in healthy cats

OBJECTIVE To determine the effect of oral administration of robenacoxib on inhibition of anterior chamber paracentesis (ACP)-induced breakdown of the blood-aqueous barrier (BAB) and assess whether robenacoxib can cross an intact BAB in healthy cats. ANIMALS 12 healthy adult domestic shorthair cats. PROCEDURES Cats received robenacoxib (6-mg tablet in a treat, PO; n = 6) or a control treatment (treat without any drug, PO; 6) once daily for 3 days, beginning 1 day before ACP. One eye of each cat served as an untreated control, whereas the other underwent ACP, during which a 30-gauge needle was used to aspirate 100 μL of aqueous humor for determination of robenacoxib concentration. Both eyes of each cat underwent anterior chamber fluorophotometry at 0 (immediately before), 6, 24, and 48 hours after ACP. Fluorescein concentration and percentage fluorescein increase were used to assess extent of ACP-induced BAB breakdown and compared between cats that did and did not receive robenacoxib. RESULTS Extent of BAB breakdown induced by ACP did not differ significantly between cats that did and did not receive robenacoxib. Low concentrations of robenacoxib were detected in the aqueous humor (mean, 5.32 ng/mL; range, 0.9 to 16 ng/mL) for 5 of the 6 cats that received the drug. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that oral administration of robenacoxib did not significantly decrease extent of BAB breakdown in healthy cats. Detection of low robenacoxib concentrations in the aqueous humor for most treated cats indicated that the drug can cross an intact BAB.

Update in feline therapeutics: clinical use of 10 emerging therapies

PRACTICAL RELEVANCE

The field of veterinary medicine is constantly evolving. New medications are being introduced into clinical practice, and novel uses for established medications are frequently being discovered as new information comes to light.

CLINICAL CHALLENGES

Therapeutic options for our feline patients can be restricted based on inadequate clinical evidence, adverse effects and patient compliance concerns. Additionally, with the reduced availability of commonly used medications in some regions, clinicians are forced to utilize alternatives with which they may have limited experience.

AUDIENCE

This review article is directed towards primary care veterinarians working with feline patients. The selection of medications discussed is based on many of the clinical challenges commonly encountered in practice.

EVIDENCE BASE

The evidence for use of some of these medications is limited due to their novelty. Known mechanisms of action, pharmacokinetic and pharmacodynamics data, adverse effects and clinical uses are reviewed where possible, with clinical recommendations made based on the evidence of data available.

The pharmacokinetics and in vitro/ex vivo cyclooxygenase selectivity of parecoxib and its active metabolite valdecoxib in cats

Parecoxib (PX) is an injectable prodrug of valdecoxib (VX, which is a selective cyclo-oxyganase-2 (COX-2)) inhibitor licensed for humans. The aim of the present study was to evaluate pharmacokinetics and in vitro/ex vivo cyclooxygenase selectivity of PX and VX in cats. In a whole blood in vitro study, PX did not affect either COX enzymes whereas VX revealed a COX-2 selective inhibitory effect in feline whole blood. The IC50 values of VX for COX-2 and COX-1 were 0.45 and 38.6 µM, respectively. Six male cats were treated with 2.5 mg/kg of PX by intramuscular injection. PX was rapidly converted to VX with a relatively short half-life of 0.4 h. VX achieved peak plasma concentration (2.79 ± 1.59 µg/mL) at 7 h following PX injection. The mean residence times for PX and VX were 0.43 ± 0.15 and 5.94 ± 0.88 h, respectively. In the ex vivo study, PX showed a COX-2 inhibition rate of about 70% in samples taken at 1, 2, 4 and 10 h after injection, with a significant difference compared to the control. In contrast, COX-1 was slightly inhibited, ranging from 0.7% to 9.7% of the control inhibition rate without any significant difference for 24 h after PX administration. The preliminary findings of the present research appear promising and encourage further studies to investigate whether PX can be successfully used in feline medicine.

Effects of route of administration and feeding schedule on pharmacokinetics of robenacoxib in cats

OBJECTIVE

To establish pharmacokinetics of robenacoxib after administration to cats via the IV, SC, and oral routes.

ANIMALS

24 cats.

PROCEDURES

In a crossover design, robenacoxib was administered IV, SC, and orally (experiment 1) and orally (experiment 2) to cats with different feeding regimens. Blood robenacoxib concentrations were assayed, with a lower limit of quantification of 3 ng/mL.

RESULTS

In experiment 1, geometric mean pharmacokinetic values after IV administration of robenacoxib were as follows: blood clearance, 0.44 L/kg/h; plasma clearance, 0.29 L/kg/h; elimination half-life, 1.49 hours; and volume of distribution at steady state (determined from estimated plasma concentrations), 0.13 L/kg. Mean bioavailability was 69% and median time to maximum concentration (Cmax) was 1 hour for cats after SC administration of robenacoxib, whereas mean bioavailability was 49% and 10% and median time to Cmax was 1 hour and 30 minutes after oral administration to cats after food withholding and after cats were fed their entire ration, respectively. In experiment 2, geometric mean Cmax was 1,159, 1,201, and 692 ng/mL and area under the curve from 0 to infinity was 1,337, 1,383, and 1,069 ng × h/mL following oral administration to cats after food withholding, cats fed one-third of the daily ration, and cats fed the entire daily ration, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

For treatment of acute conditions in cats, it is recommended to administer robenacoxib by IV or SC injection, orally after food withholding, or orally with a small amount of food to obtain optimal bioavailability and Cmax.

The effect of robenacoxib on the concentration of C-reactive protein in synovial fluid from dogs with osteoarthritis

Background

Robenacoxib is a novel and highly selective inhibitor of COX-2 in dogs and cats and because of its acidic nature is regarded as being tissue-selective. Thirty four dogs with stifle osteoarthritis secondary to failure of the cranial cruciate ligament were recruited into this study. Lameness, radiographic features, synovial cytology and C-reactive protein concentrations in serum and synovial fluid were assessed before and 28 days after commencing a course of Robenacoxib at a dose of 1 mg/kg SID.

Results

There was a significant reduction in the lameness score (P < 0.01) and an increase in the radiographic score (P < 0.05) between pre- and post-treatment assessments. There was no difference between pre- (median 1.49 mg/l; Q1-Q3 0.56-4.24 mg/L) and post – (1.10 mg/L; 0.31-1.78 mg/L) treatment serum C-reactive protein levels although synovial fluid levels were significantly reduced (pre- : 0.44 mg/L; 0.23-1.62 mg/L; post- : 0.17 mg/L; 0.05-0.49 mg/L) (P < 0.05). There was no correlation between C-reactive protein concentrations in serum and matched synovial fluid samples.

Conclusions

Robenacoxib proved effective in reducing lameness in dogs with failure of the cranial cruciate ligament and osteoarthritis of the stifle joint. The drug also reduced levels of C-reactive protein in the synovial fluid taken from the affected stifle joint. Robenacoxib appears to reduce articular inflammation as assessed by C-reactive protein which supports the concept that Robenacoxib is a tissue-selective non-steroidal anti-inflammatory drug.

Comparison of the analgesic effects of robenacoxib, buprenorphine and their combination in cats after ovariohysterectomy

The aim of this study was to compare the postoperative analgesic effects of robenacoxib and buprenorphine alone or in combination, in cats after ovariohysterectomy. Thirty healthy cats were randomly assigned to receive buprenorphine (0.02 mg/kg, n=10; GB), robenacoxib (2mg/kg, n=10; GR) or their combination at the same dosages (n=10; GBR) SC. After 30 min cats were sedated with an IM administration of medetomidine (0.02 mg/kg) and ketamine (5mg/kg). General anaesthesia was induced with propofol and after intubation was maintained with isoflurane. Before premedication and at 1, 2, 3, 4, 6, 8, 12 and 24h after extubation, pain and sedation were assessed using a simple descriptive pain scale, ranging from 0 (no pain/no sedation) to 4 (intense pain/ deep sedation). If the pain score was ≥ 3, rescue analgesia was provided using buprenorphine (0.02 mg/kg) administered IM. Pain score was higher in GB at 2, 3, 4, 6 and 8h compared to baseline and compared to GBR at the same study times. Moreover, the pain score was also higher in GB compared to GR at 2, 3, 4 and 6h. Pain score was similar at all study times between GR and GBR. Sedation at 1 and 2h was higher than baseline values in all groups. Cats in GB received rescue analgesia more often than cats assigned to GR or GBR. Robenacoxib was an effective analgesic drug in cats up to 24h after ovariohysterectomy. The addition of buprenorphine did not provide any additional analgesic effects compared to robenacoxib alone.

Potency and selectivity of carprofen enantiomers for inhibition of bovine cyclooxygenase in whole blood assays

Whole blood in vitro assays were used to determine the potency and selectivity of carprofen enantiomers for inhibition of the isoforms of cyclooxygenase (COX), COX-1 and COX-2, in the calf. S(+)-carprofen possessed preferential activity for COX-2 inhibition but, because the slopes of inhibition curves differed, the COX-1:COX-2 inhibition ratio decreased from 9.04:1 for inhibitory concentration (IC)10 to 1.84:1 for IC95. R(-) carprofen inhibited COX-2 preferentially only for low inhibition of the COX isoforms (IC10 COX-1:COX-2=6.63:1), whereas inhibition was preferential for COX-1 for a high level of inhibition (IC95 COX-1:COX-2=0.20:1). S(+) carprofen was the more potent inhibitor of COX isoforms; potency ratios S(+):R(-) carprofen were 11.6:1 for IC10 and 218:1 for IC90. Based on serum concentrations of carprofen enantiomers obtained after administration of a therapeutic dose of 1.4 mg/kg to calves subcutaneously, S(+)-carprofen concentrations exceeded the in vitro IC80 COX-2 value for 32 h and the IC20 for COX-1 for 33 h. The findings are discussed in relation to efficacy and safety of carprofen in calves.

Clinical pharmacology of nonsteroidal anti-inflammatory drugs in dogs

OBJECTIVES

To discuss the clinical pharmacology of currently licensed veterinary NSAIDs and to review gastrointestinal and renal adverse effects as well as drug-drug interactions that have been reported with these drugs. To review the use of NSAIDs in the peri-operative setting and their use in patients with osteoarthritis. To further review the reported effects of NSAIDs on canine articular cartilage and liver as well as the clinical relevance of a washout period.

DATABASES USED

PubMed, CAB abstracts and Google Scholar using dog, dogs, nonsteroidal anti-inflammatory drugs and NSAID(s) as keywords.

CONCLUSIONS

A good understanding of the mechanisms by which NSAIDs elicit their analgesic effect is essential in order to minimize adverse effects and drug-drug interactions. Cyclooxygenase (COX) is present in at least two active isoforms in the body and is the primary pharmacologic target of NSAIDs. Inhibition of COX is associated with the analgesic effects of NSAIDs. COX is present in the gastrointestinal tract and kidneys, along with other areas of the body, and is also the likely reason for many adverse effects including gastrointestinal and renal adverse effects. The newer veterinary approved NSAIDs have a lower frequency of gastrointestinal adverse effects in dogs compared to drugs such as aspirin, ketoprofen and flunixin, which may be due to differential effects on the COX isoforms. There are currently no published reports demonstrating that the newer NSAIDs are associated with fewer renal or hepatic adverse effects in dogs. NSAIDs remain the cornerstone of oral therapy for osteoarthritis unless contraindicated by intolerance, concurrent therapies or underlying medical conditions. NSAIDs are also effective and frequently used for the management of post-operative pain.

Lack of inhibitory effect of acetylsalicylic acid and meloxicam on whole blood platelet aggregation in cats

OBJECTIVE

To determine the effects of acetylsalicylic acid (ASA) and meloxicam on feline platelet aggregation and associated platelet thromboxane production and serotonin release.

DESIGN

Prospective interventional study.

SETTING

University research facility.

ANIMALS

Eight healthy male castrated domestic short hair cats from a research colony.

INTERVENTIONS

Oral medications were administered to 8 cats for 14 days in a randomized, placebo-controlled, crossover design. Treatment groups included: aspirin (ASA) (5 mg/kg q 48 h), meloxicam (0.05 mg/kg q 24 h), and placebo (0.5 mL of water q 24 h). Thromboxane assays (TXB(2) ) and whole blood (impedance) aggregometry (WBA) were performed on samples collected before drug administration, and on days 7, 15, and 17, using adenosine diphosphate (ADP; 10 μM) and collagen (5 μg/mL) as agonists for WBA. Serotonin release was assayed on postaggregation plasma. Oral mucosal bleeding time (OMBT) and complete blood cell counts were measured on days 0 and 15.

MEASUREMENTS AND MAIN RESULTS

Neither medication affected WBA at any time point. OMBT decreased in the ASA group relative to baseline. No differences were detected in WBA and OMBT baseline between any groups. No difference was detected in serotonin secretion at any time point. TXB(2) was significantly decreased in the ASA group at all times after initiation of treatment but no change was noted in the meloxicam or placebo groups.

CONCLUSIONS

At the doses studied, neither meloxicam nor ASA had an inhibitory effect on WBA or OMBT in cats. Thromboxane concentrations were significantly decreased with ASA treatment.

Population pharmacokinetic analysis of blood and joint synovial fluid concentrations of robenacoxib from healthy dogs and dogs with osteoarthritis

PURPOSE

The purpose of this population analysis was to characterize the pharmacokinetic properties of robenacoxib in blood and stifle joint synovial fluid of dogs.

METHODS

Data were obtained from two studies: 1) 8 healthy Beagle dogs in which an acute inflammation was induced by injection of urate crystals into one joint; 2) 95 dogs from various breeds diagnosed with osteoarthritis (OA). Robenacoxib concentrations in blood and synovial fluid were measured using a validated HPLC-UV and LC-MS method. Non-linear mixed effects modeling was performed using NONMEM6.

RESULTS

A two-compartment pharmacokinetic model with linear elimination was developed to describe blood concentrations of robenacoxib. Blood clearance in healthy animals was found to be 75% higher than in OA dogs. Synovial fluid concentrations were modeled using an effect-compartment-type model predicting longer residence times in OA dogs compared to healthy Beagles (e.g. concentrations above the IC(50) for COX-2, respectively, 16 h vs. 10 h at 1.5 mg/kg).

CONCLUSIONS

Robenacoxib was found to reside longer at the effect site (inflamed joint) compared to blood in both healthy and OA dogs. These results may explain the good efficacy observed with once-daily dosing in clinical trials and the high safety index of robenacoxib in dogs.

Long-term pain in cats: how much do we know about this important welfare issue?

PRACTICAL RELEVANCE

Long-term pain in cats is an important welfare issue but is often overlooked and undertreated.

AUDIENCE

All practitioners are faced with cats that require analgesic intervention to improve their quality of life.

PATIENT GROUP

Any cat may potentially experience long-term pain and discomfort. Degenerative joint disease and diabetic-related pain is more common in middle-aged or older individuals, whereas persistent postsurgical pain can occur at any age and is seen in young cats following onychectomy.

EVIDENCE BASE

Robust evidence on long-term pain issues in cats - specifically, relating to prevalence, etiology, and treatment protocols and outcomes - is missing from the veterinary literature. The aim of this review is to summarise the current state of knowledge. In doing so, it takes a practical approach, highlighting the obvious, and some not so obvious, causes of long-term pain in cats; some aspects that warrant closer attention; our ability to recognize pain and monitor how this impacts on quality of life; and today's treatment options.

DJD-associated pain in cats: what can we do to promote patient comfort?

PRACTICAL RELEVANCE

Degenerative joint disease (DJD) has a high prevalence in domestic cats and can be associated with pain. This pain should be addressed wherever possible.

AUDIENCE

All practitioners are faced with cats that are mobility impaired due to DJD-associated pain.

PATIENT GROUP

Cats of all ages and breeds, and either sex, can experience DJD-associated discomfort.

CLINICAL CHALLENGES

Recognizing DJD and assessing DJD-associated pain in cats is a challenge. Owner observations of activity and behavior, careful observation and a logical and thorough orthopedic evaluation are key. Current understanding of the etiology of feline DJD and the mechanisms of DJD-associated pain is incomplete, making the rational choice of treatments a further challenge.

EVIDENCE BASE

Evidence is emerging on the prevalence of feline DJD, and on how to assess the associated pain and mobility impairment. There is a lack of information on the etiology of feline DJD and a relative lack of data on the efficacy of putative treatments.

In vitro and ex vivo inhibition of canine cyclooxygenase isoforms by robenacoxib: a comparative study

In vitro whole blood canine assays were used to quantify the inhibitory actions of the novel non-steroidal anti-inflammatory drug (NSAID) robenacoxib on the cyclooxygenase (COX) isoenzymes, COX-1 and COX-2, in comparison with other drugs of the NSAID class. COX-1 activity was determined by measuring serum thromboxane (Tx)B(2) synthesis in blood samples allowed to clot at 37 degrees C for 1h. COX-2 activity was determined by measuring prostaglandin (PG)E(2) synthesis in blood samples incubated at 37 degrees C for 24h in the presence of lipopolysaccharide. The rank order of selectivity for inhibition of COX-2 versus COX-1 (IC(50) COX-1:IC(50) COX-2) for veterinary drugs was highest with robenacoxib (128.8) compared to deracoxib (48.5), nimesulide (29.2), S+ carprofen (17.6), meloxicam (7.3), etodolac (6.6), R- carprofen (5.8) and ketoprofen (0.88). Selectivity expressed as the clinically relevant ratio IC(20) COX-1:IC(80) COX-2 was highest for robenacoxib (19.8) compared to deracoxib (2.3), S+ carprofen (2.5), R- carprofen (2.1), nimesulide (1.8), etodolac (0.76), meloxicam (0.46) and ketoprofen (0.21). An in vivo pharmacokinetic ex vivo pharmacodynamic study in the dog established dosage and concentration-effect relationships for single oral doses of robenacoxib over the dosage range 0.5-8.0mg/kg. Values of C(max) and AUC were linearly related to dosage over the tested range. Robenacoxib did not inhibit serum TxB(2) synthesis (COX-1) ex vivo at dosages of 0.5-4.0mg/kg and produced only transient inhibition (at the 1h and 2h sampling times) at the 8mg/kg dosage. All dosages of robenacoxib (0.5-8mg/kg) produced marked, significant and dose related inhibition of PGE(2) synthesis (COX-2) ex vivo. The data demonstrate that in the dog robenacoxib is a highly selective inhibitor of the COX-2 isoform of COX, and significantly inhibits COX-2 and spares COX-1 in vivo when administered orally over the dosage range 0.5-4.0mg/kg.

Use of a pharmacokinetic/pharmacodynamic approach in the cat to determine a dosage regimen for the COX-2 selective drug robenacoxib

This study investigated the analgesic, anti-inflammatory and antipyretic efficacy of the new COX-2 selective inhibitor robenacoxib in the cat and established pharmacodynamic (PD) parameters for these effects. Robenacoxib, at a dosage of 2 mg/kg administered subcutaneously, was evaluated in a kaolin-induced paw inflammation model in 10 cats, using both clinically relevant endpoints (lameness scoring, locomotion tests) and other indicators of inflammation (body and skin temperature, thermal pain threshold) to establish its pharmacological profile. A pharmacokinetic/pharmacodynamic (PK/PD) modelling approach, based on indirect response models, was used to describe the time course and magnitude of the responses to robenacoxib. All endpoints demonstrated good responsiveness to robenacoxib administration and both the magnitude and time courses of responses were well described by the indirect pharmacodynamic response models. Pharmacokinetic and clinically relevant pharmacodynamic parameters were used to simulate dosage regimens that will assist the planning of clinical trials and the selection of an optimal dosage regimen for robenacoxib in the cat.