Pharmacology of drugs used to treat osteoarthritis in veterinary practice

The Clinical Pharmacology and Therapeutic Evaluation of Non-Steroidal Anti-Inflammatory Drugs in Adult Horses

This review firstly examines the underlying pathophysiology of pain and inflammation associated with orthopedic disease and endotoxemia. Then, it reviews the clinical pharmacology (pharmacokinetics and pharmacodynamics) of both conventional and non-conventional NSAIDs in the adult horse, and finally provides an overview of different modalities to evaluate the therapeutic efficacy of NSAIDs in research.

Advancing animal health and disease research in the lab with three-dimensional cell culture systems

The development of three-dimensional cell culture systems representative of tissues from animals of veterinary interest is accelerating research that seeks to address specific questions tied to animal health. In terms of their relevance and complexity, these in vitro models can be seen as a midpoint between the more reductionist single-cell culture systems and complex live animals. Organoids in particular represent a significant development due to their organised multicellular structure that more closely represents in vivo tissues than any other cell culture technology previously developed. In this review, we provide an overview of the different three-dimensional cell culture systems available to veterinary researchers and give examples of their application in contexts relating to animal health.

Comparison of clinical and radiographic signs of hip osteoarthritis in contralateral hip joints of fifty working dogs

OBJECTIVE

This study aimed to compare the symmetry of clinical and radiographic signs of right and left pelvic limbs of dogs with bilateral hip osteoarthritis (OA) and evaluate the association of physical findings and radiographic abnormalities.

PATIENTS AND METHODS

One hundred pelvic limbs of police working dogs with bilateral hip OA were evaluated, following a screening program. Weight distribution, joint range of motion at flexion and extension, thigh girth, and radiographic signs were recorded and compared with the results of the contralateral limb and by breed, age, and sex with the Paired Samples T-Test and Pearson correlation coefficient, with p<0.05.

RESULTS

The sample mean age was 6.5±2.2 years, and the bodyweight of 26.7±5.3kg. No significant differences were observed when comparing weight distribution, joint range of motion, and thigh girth of left and right limbs. Weight distribution and age showed a statistically significant correlation with joint extension. The right limbs showed a significantly higher frequency of circumferential femoral head osteophyte (CFHO) regarding radiographic signs. Limbs with CFHO or caudolateral curvilinear osteophyte had significantly larger joint flexion angle (p = 0.02) and smaller extension angle (p<0.01), respectively, compared to those that did not. Age showed a significant correlation with the presence of several radiographic findings, as did different breeds.

CONCLUSION

Clinical and radiographic signs occur symmetrically in naturally occurring hip OA in police working dogs. Several correlations were observed between the evaluations performed and differences between breeds, which can be useful in assessing and early diagnosis of hip OA.

Andrographolide Exerts Chondroprotective Activity in Equine Cartilage Explant and Suppresses Interleukin-1 β -Induced MMP-2 Expression in Equine Chondrocyte Culture

Cartilage erosion in degenerative joint diseases leads to lameness in affected horses. It has been reported that andrographolide from Andrographis paniculata inhibited cartilage matrix-degrading enzymes. This study aimed to explore whether this compound protects equine cartilage degradation in the explant culture model and to determine its effect on matrix metalloproteinase-2 (MMP-2) expression, a matrix-degrading enzyme, in equine chondrocyte culture. Equine articular cartilage explant culture was induced by 25 ng/mL interleukin-1β, a key inducer of cartilage degeneration, in cultures with or without andrographolide ranging from 10 to 50 μM. After 3–21 days, they were analyzed for the markers of cartilage degradation. It was found that interleukin-1β increased the release of sulfated glycosaminoglycans and hyaluronan from the explants into the culture media consistently with the decrease in uronic acid and collagen content in the cartilage explants. These catabolic effects were inhibited when cotreated with interleukin-1β and andrographolide. In primary equine chondrocytes, andrographolide suppressed interleukin-1β-induced MMP-2 mRNA expression and MMP-2 activity in the culture medium. These results confirmed the in vitro potent chondroprotective activities of this compound which were performed in cartilage explants and on a cellular level. These may indicate the application of andrographolide for therapeutic use in equine degenerative joint diseases.

Scientific evidence and rationale for the development of curcumin and resveratrol as nutraceutricals for joint health

Interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α) are key cytokines that drive the production of inflammatory mediators and matrix-degrading enzymes in osteoarthritis (OA). These proinflammatory cytokines bind to their respective cell surface receptors and activate inflammatory signaling pathways culminating with the activation of nuclear factor κB (NF-κB), a transcription factor that can be triggered by a host of stress-related stimuli including, excessive mechanical stress and ECM degradation products. Once activated, NF-κB regulates the expression of many cytokines, chemokines, adhesion molecules, inflammatory mediators, and several matrix-degrading enzymes. Therefore, proinflammatory cytokines, their cell surface receptors, NF-κB and downstream signaling pathways are therapeutic targets in OA. This paper critically reviews the recent literature and outlines the potential prophylactic properties of plant-derived phytochemicals such as curcumin and resveratrol for targeting NF-κB signaling and inflammation in OA to determine whether these phytochemicals can be used as functional foods.

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.

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

Robenacoxib is a new nonsteroidal anti-inflammatory drug (NSAID) developed for use in companion animal medicine. The objectives of this study were: to quantify the inhibitory actions of robenacoxib on cyclooxygenase (COX) isoenzymes in feline whole blood assays; to establish blood concentration-time profiles of robenacoxib after intravenous and subcutaneous dosing in the cat and; to predict the time courses of inhibition of COX isoforms by robenacoxib. COX-1 and COX-2 activities in heparinized feline whole blood samples were induced with calcium ionophore and lipopolysaccharide, respectively. Inhibition of thromboxane B2 provided a marker of both COX-1 and COX-2 activities and a nonlinear parametric mixed effects modelling approach was used to establish the pharmacodynamic parameters describing this inhibition. Mean values (and prediction intervals) of IC50 were 28.9 (16.4-51.1) microM (COX-1) and 0.058 (0.010-0.340) microM (COX-2). These parameters were used to compute several selectivity indices. Selectivity IC ratios (COX-1:COX-2) were 502.3 (IC50/IC50), 451.6 (IC95/IC95) and 17.05 (IC20/IC80). Based on a clinically recommended dosage regimen of 2 mg/kg, it was predicted that the corresponding mean robenacoxib blood concentration over the first 12 h after drug administration corresponded to 5% inhibition of COX-1 and 90% inhibition of COX-2.

The contribution of the synovium, synovial derived inflammatory cytokines and neuropeptides to the pathogenesis of osteoarthritis

Osteoarthritis (OA) is one of the most common and disabling chronic joint disorders affecting horses, dogs and humans. Synovial inflammation or synovitis is a frequently observed phenomenon in osteoarthritic joints and contributes to the pathogenesis of OA through formation of various catabolic and pro-inflammatory mediators altering the balance of cartilage matrix degradation and repair. Catabolic mediators produced by the inflamed synovium include pro-inflammatory cytokines, nitric oxide, prostaglandin E(2) and several neuropeptides, which further contribute to the pathogenesis of OA by increasing cartilage degradation. Recent studies suggest that substance P, corticotropin-releasing factor, urocortin and vasoactive intestinal peptide may also be involved in OA development, but the precise role of these neuropeptides in the pathogenesis of OA is not known. Since increased production of matrix metalloproteinases by the synovium is stimulated by pro-inflammatory cytokines, future anti-inflammatory therapies should focus on the synovium as a means of controlling subsequent inflammatory damage.

Pharmacokinetic/pharmacodynamic modelling of NSAIDs in a model of reversible inflammation in the cat

1 Data on the relationships between plasma concentration and analgesic and anti-inflammatory effects of NSAIDs are limited because most inflammation models do not permit pharmacokinetic/pharmacodynamic (PK/PD) modelling to be readily performed. 2 In this study, a kaolin-induced inflammation model in the cat was evaluated for pre-clinical characterization of the pharmacodynamic profiles of NSAIDs (determination of efficacy, potency, sensitivity (that is the slope of the concentration-effect relationship) and duration of drug response), using meloxicam as a probe article. 3 Indirect response PK/PD models described the time course and magnitude of responses produced by 0.3 mg kg(-1) meloxicam administered subcutaneously. For endpoints for which spontaneous recovery from inflammation was superimposed on drug response, a PK/PD model with a time-dependent K(in) was used to allow for the spontaneous changes of the inflammation with time. 4 The selected endpoints were suitable for studying simultaneously the analgesic, anti-inflammatory and antipyretic effects of meloxicam, allowing comparison of relative potencies for these effects. Mean+/-s.d. IC(50) or EC(50) values (ng ml(-1)) were 777+/-124 (body temperature), 841+/-187 (locomotion variable), 883+/-215 (pain score), 911+/-189 (lameness score) and 1298+/-449 (skin temperature difference). Corresponding mean times+/-s.d. of peak responses (h) were 5.6+/-1.3, 8.6+/-3.8, 5.2+/-5.0, 5.6+/-3.7 and 4.3+/-2.4, respectively. 5 As the pharmacokinetic profiles of meloxicam in cats and humans are similar, simulations of several dosage regimens in the cat provided a pre-clinical basis, illustrating the value of the cat model for predicting a clinical dose regimen for evaluation in man. The predicted loading doses (mg kg(-1)) of meloxicam in the cat producing 70% of the maximum attainable responses were 0.29 (body temperature), 0.32 (lameness score), 0.33 (overall locomotion variable), 0.36 (pain score) and 0.50 (skin temperature difference). The values are similar to or somewhat greater than the clinically recommended doses both in cats (0.3 mg kg(-1)) and humans (7.5-15 mg, that is, between 0.1 and 0.3 mg kg(-1)). 6 These findings indicate the potential value of the cat as a laboratory model, and of a PK/PD modelling approach in assisting NSAID development programs in animals and humans.

Pharmacokinetic and pharmacodynamic interactions of tolfenamic acid and marbofloxacin in goats

Pharmacokinetic and pharmacodynamic properties in goats of the non-steroidal anti-inflammatory drug tolfenamic acid (TA), administered both alone and in combination with the fluoroquinolone marbofloxacin (MB), were established in a tissue cage model of acute inflammation. Both drugs were injected intramuscularly at a dose rate of 2 mg kg(-1). After administration of TA alone and TA+MB pharmacokinetic parameters of TA (mean values) were Cmax=1.635 and 1.125 microg ml(-1), AUC=6.451 and 3.967 microgh ml(-1), t1/2K10=2.618 and 2.291 h, Vdarea/F=1.390 and 1.725Lkg(-1), and ClB/F=0.386 and 0.552 L kg(-1) h(-1), respectively. These differences were not statistically significant. Tolfenamic acid inhibited prostaglandin (PG)E2 synthesis in vivo in inflammatory exudate by 53-86% for up to 48 h after both TA treatments. Inhibition of synthesis of serum thromboxane (Tx)B2 ex vivo ranged from 16% to 66% up to 12h after both TA and TA+MB, with no significant differences between the two treatments. From the pharmacokinetic and eicosanoid inhibition data for TA, pharmacodynamic parameters after dosing with TA alone for serum TxB2 and exudate PGE2 expressing efficacy (Emax=69.4 and 89.7%), potency (IC50=0.717 and 0.073 microg ml(-1)), sensitivity (N=3.413 and 1.180) and equilibration time (t1/2Ke0=0.702 and 16.52 h), respectively, were determined by PK-PD modeling using an effect compartment model. In this model TA was a preferential inhibitor of COX-2 (COX-1:COX-2 IC50 ratio=12:1). Tolfenamic acid, both alone and co-administered with MB, did not affect leucocyte numbers in exudate, transudate or blood. Compared to placebo significant attenuation of skin temperature rise over inflamed tissue cages was obtained after administration of TA and TA+MB with no significant differences between the two treatments. Marbofloxacin alone did not significantly affect serum TxB2 and exudate PGE2 concentrations or rise in skin temperature over exudate tissue cages. These data provide a basis for the rational use of TA in combination with MB in goat medicine.

Development and validation of a new model of inflammation in the cat and selection of surrogate endpoints for testing anti-inflammatory drugs

In laboratory animals many models of inflammation have been developed for preclinical evaluation of the pharmacological profiles of nonsteroidal anti-inflammatory drugs (NSAIDs). In contrast, in species of veterinary interest, including the cat, NSAIDs have been studied mainly using dose-titration or dose-confirmation studies in clinical subjects. This is due to the scarcity of appropriate animal models and to the associated lack of quantitative validated endpoints describing the magnitude and time course of drug response. Determination of pharmacokinetic/pharmacodynamic (PK/PD) relationships provides a powerful approach for the selection of effective and safe dosage regimens. In this study, a paw inflammation model in the cat was developed for the preclinical evaluation of NSAIDs using PK/PD modelling. Subcutaneous injection of 500 mg kaolin in the paw produced a well-defined and reproducible inflammatory response that lasted 4-5 days. Several endpoints were assessed for their clinical relevance and for their metrological performance (accuracy and reproducibility). Body temperature, lameness scoring, locomotion tests and possibly skin temperature were the most appropriate endpoints for testing the antipyretic, analgesic and anti-inflammatory effects of NSAIDs in the cat.

Influence of marbofloxacin on the pharmacokinetics and pharmacodynamics of tolfenamic acid in calves

Pharmacokinetic and pharmacodynamic properties of tolfenamic acid (TA) in calves were determined in serum and fluids of inflamed (carrageenan administered) and non-inflamed subcutaneously implanted tissue cages after intramuscular administration both alone and in combination with marbofloxacin (MB). MB significantly altered the pharmacokinetics of TA: mean values were Cmax = 2.14 and 1.64 microg/mL, AUC = 27.38 and 16.80 microg.h/mL, Vd(area)/F = 0.87 and 1.17 L/kg, and ClB/F = 0.074 and 0.128 L/kg/h, respectively, after administration of TA alone and TA + MB. T(1/2)K10 and MRT were not significantly different for the two treatments. The pharmacodynamic properties of TA were not influenced by MB co-administration, in spite of the alterations in some TA pharmacokinetic parameters. TA inhibited prostaglandin E2 (PGE2) synthesis in vivo in inflammatory exudate by 50-88% for up to 48 h after both TA treatments. Inhibition of synthesis of serum thromboxane B2 (TxB2) ex vivo ranged from 40 to 85% up to 24 h after both TA and TA + MB. From the derived pharmacokinetic and eicosanoid inhibition data for TA, pharmacodynamic parameters for serum TxB2 and exudate PGE2 inhibition expressing efficacy (Emax = 78.1 and 97.5%), potency (IC50 = 0.256 and 0.265 microg/mL), sensitivity (N = 1.96 and 2.29) and the pharmacokinetic parameter equilibration time (t(1/2)K(e0) = 0.695 and 24.0 h), respectively, were determined. In this model TA was a nonselective inhibitor of cyclo-oxygenase (COX) (COX-1:COX-2 IC50 ratio = 1.37). TA, both alone and co-administered with MB, did not affect leucocyte numbers in exudate, transudate or blood. Partial attenuation of skin temperature rise over inflamed tissue cages and reduction of zymosan-induced skin swelling were recorded after administration of TA and TA + MB with no significant differences between the two treatments. These data provide a basis for the rational use of TA in combination with MB in calf medicine.

Integration and modelling of pharmacokinetic and pharmacodynamic data to optimize dosage regimens in veterinary medicine

In veterinary drug development procedures, pharmacokinetic (PK) and pharmacodynamic (PD) data have generally been established in separate, parallel studies to assist in the design of dosage schedules for subsequent evaluation in clinical trials. This review introduces the concept of PK/PD modelling, an approach in which PK and PD data are generated in the same study, and used to derive numerical values for PD parameters based on drug plasma concentrations. The PD parameters define the efficacy, potency and slope (sensitivity) of the concentration-effect relationship. It is proposed that the parameters derived from PK/PD modelling may be used as an alternative and preferred approach to dose titration studies for selecting rational dosage regimens (both dose and dosing interval) for further evaluation in clinical trials. In PK/PD modelling, the explicative variable for effect is the plasma concentration profile. The PK/PD approach provides several advantages over dose-titration studies, including determination of a projected dosage regimen by investigation of a single dose, in contrast to dose-ranging studies which by definition require testing of multiple dosage. Implementation of PK/PD modelling in the veterinary drug development process is currently constrained by the limited number of veterinary studies performed to date, and the consequently limited understanding of PK/PD concepts and their absence from regulatory authority guidelines. Nevertheless, PK/PD modelling has major potential for rational dosage regimen determination, as it considers and quantifies the two main sources of interspecies variability (PK and PD). It is therefore applicable to interspecies extrapolation and to multiple species drug development. As well as the currently limited appreciation of PK/PD principles in the veterinary scientific community, a further constraint in implementing PK/PD modelling is the need to validate PK/PD approaches and thereby gain confidence in its value by pharmaceutical companies and regulatory authorities.

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.

Clinical efficacy of carprofen as an adjunct to the antibacterial treatment of bovine respiratory disease

A clinical trial was undertaken to investigate the efficacy of a single dose of carprofen (CPF) in the treatment of bovine respiratory disease in cattle. Tilmicosin was used as a basal treatment in all animals. Six hours after dosing, body temperature and respiratory rates in animals treated with CPF-tilmicosin had decreased and were significantly lower than in the animals treated with tilmicosin alone (P < 0.05). Over the period of clinical observation, CPF-tilmicosin treatment produced a clinical resolution of the pneumonia similar to treatment with tilmicosin alone. However, it is significant from an animal welfare perspective that over the period of the study after treatment, CPF-tilmicosin therapy produced significantly greater symptomatic improvement than tilmicosin.