Field Trial Validation of the Efficacy and Acceptability of Firocoxib, a Highly Selective Cox-2 Inhibitor, in a Group of 96 Lame Horses

Long-Term Firocoxib Use in Horses

BACKGROUND

Many horses receive firocoxib over multiple years, and studies evaluating hematologic and biochemical values in these animals are lacking.

OBJECTIVE

To describe the hematologic and biochemical values of horses receiving long-term firocoxib.

ANIMALS

A total of 79 horses receiving long-term firocoxib and 153 horses not receiving long-term firocoxib and not presenting for a specific medical problem.

METHODS

Retrospective study comparing horses receiving firocoxib (F group) and no firocoxib (NF group). Signalment, hematologic, and biochemical values were compared between the two groups. Simple linear regression was used to evaluate the relationship between the duration of firocoxib administration and specific laboratory variables.

RESULTS

Horses receiving long-term firocoxib (F) were 19 (5-33) years as compared to 15 (1-33) years for the NF group (p < 0.0001). The most common reason for receiving firocoxib was osteoarthritis in 44/79 (56%) of the animals in the F group. Horses in the F group had a total protein concentration of 6.6 (5.8-8.0) g/dL as compared to 6.5 (5.1-8) g/dL in the NF group (p = 0.03). The sodium concentration for F horses was 139 (133-143) mmol/L as compared to 138 (129-145) mmol/L for NF horses (p = 0.01). Total white blood cell count was 6.11 (2.82-14.36) 103 cells/uL in the F group as compared to 6.46 (3.04-14.71) 103 cells/uL in the NF group (p = 0.03). None of the laboratory variables were associated with the duration of firocoxib administration.

CONCLUSIONS AND CLINICAL IMPORTANCE

Many horses receive firocoxib for multiple years, and equine practitioners should be aware that expected changes in laboratory values are minimal.

Safety Assessment of an Oral Therapeutic Dose of Firocoxib on Healthy Horses

Firocoxib is a non-steroidal anti-inflammatory drug specifically formulated for veterinary medicine and selectively acts on inhibiting the cyclooxygenase 2 enzyme (COX-2). This study evaluated the possible adverse effects of administering oral therapeutic firocoxib on gastric mucosa, hematological parameters, coagulation cascade, and hepatic and renal biochemistry in healthy horses. Nine clinically healthy Arabian horses, approximately 9 years old, received 0.1 mg/kg of oral firocoxib for 14 days. The gastroscopic examination was conducted 1 day before starting treatment (D0) and two days after the last blood collection (D23). Venous blood samples were obtained for laboratory tests on day 1, immediately prior to the initiation of treatment (D1), after 7 and 14 days of treatment (D7 and D14), and 7 days after the conclusion of treatment (D21. No changes were found in the gastroscopic and hematological tests. Coagulation and serum biochemistry levels remain between these species' average values. However, the increased activated partial thromboplastin time (aPTT) and prothrombin time (PT) indicate reduced blood coagulation capacity, which contradicts the expected effect of treatment with selective COX-2 inhibitors, as these drugs theoretically promote coagulation. Administering firocoxib to horses is safe as it does not cause significant adverse reactions. Therefore, it is a suitable option for managing inflammatory conditions in these animals with attention to an unexpected adverse anti-coagulopathy effect, and further study is warranted.

Synopsis of the pharmacokinetics, pharmacodynamics, applications, and safety of firocoxib in horses

According to in vitro and in vivo investigations, firocoxib (FX), a second-generation coxib, is a highly selective COX-2 inhibitor in horses. With a COX-1/COX-2 IC₅₀ ratio of 643 in horses, FX spares the COX-1 inhibitory effects. It is approved for the treatment of musculoskeletal problems and lameness in horses and dogs with osteoarthritis (OA). For the treatment of OA in horses, both an injectable formulation for IV administration at a dose of 0.09 mg/kg for five days and an oral paste formulation at a dose of 0.1 mg/kg for 14 days are licensed. Numerous analytical methods were reported in the literature to quantify FX in biological fluids, using HPLC and LC-MS. FX presents remarkable pharmacokinetics and pharmacodynamics compared to other coxibs. It has an oral bioavailability of 80% or higher and is effectively absorbed by horses. Its volume of distribution is around 2 L/kg, and it is slowly eliminated. Due to the long elimination half-life (around 2 days), which allows a once daily dosing, a single 0.3 mg/kg loading dose has been recommended. This enables the establishment of steady-state drug concentrations within 24 h, making it appropriate for acute treatment as well. Its IC₈₀ is equal to 103 ng/mL in whole blood and, with an EC₅₀ of 27 ng/mL, it has the highest affinity for its receptor compared to the other commonly administered NSAIDs in horses.

BEVA primary care clinical guidelines: Analgesia

Primary care guidelines provide a reference point to guide clinicians based on a systematic review of the literature, contextualised by expert clinical opinion. These guidelines develop a modification of the GRADE framework for assessment of research evidence (vetGRADE) and applied this to a range of clinical scenarios regarding use of analgesic agents. Key guidelines produced by the panel included recommendations that horses undergoing routine castration should receive intratesticular local anaesthesia irrespective of methods adopted and that horses should receive NSAIDs prior to surgery (overall certainty levels high). Butorphanol and buprenorphine should not be considered appropriate as sole analgesic for such procedures (high certainty). The panel recommend the continuation of analgesia for 3 days following castration (moderate certainty) and conclude that phenylbutazone provided superior analgesia to meloxicam and firocoxib for hoof pain/laminitis (moderate certainty), but that enhanced efficacy has not been demonstrated for joint pain. In horses with colic, flunixin and firocoxib are considered to provide more effective analgesia than meloxicam or phenylbutazone (moderate certainty). Given the risk of adverse events of all classes of analgesic, these agents should be used only under the control of a veterinary surgeon who has fully evaluated a horse and developed a therapeutic, analgesic plan that includes ongoing monitoring for such adverse events such as the development of right dorsal colitis with all classes of NSAID and spontaneous locomotor activity and potentially ileus with opiates. Finally, the panel call for the development of a single properly validated composite pain score for horses to allow accurate comparisons between medications in a robust manner.

Periovulatory administration of firocoxib did not alter ovulation rates and mitigated post-breeding inflammatory response in mares

Non-steroidal anti-inflammatory drugs (NSAIDs) are a therapeutic option for the treatment of inflammation. However, negative effects of non-selective NSAIDs for treatment of mares with endometritis have been described, including delayed uterine clearance and impairment of ovulations. Firocoxib is a specific cyclooxygenase-2 (COX-2) inhibitor and has the ability to act in the uterus of mares. We investigated the effects of firocoxib on ovulation rate, numbers of polymorphonuclear neutrophils (PMNs), and COX-2 protein levels in the endometrial tissue of susceptible mares after insemination. Two experiments were conducted. In experiment 1, twenty mares were evaluated in two consecutive estrous cycles broken into the following groups: Control - no pharmacological interference; Treatment - mares were treated with 0.2 mg/kg of firocoxib orally. The treatment began on the day of ovulation induction, and firocoxib was administered until one day after artificial insemination (AI). Ovulation was induced with 1 mg of deslorelin acetate and the mares were inseminated 24 h after the injection. Ovulation was confirmed 48 h after induction, and embryos were collected eight days after ovulation. Experiment 2: Nine mares susceptible to persistent mating-induced endometritis (PMIE) were artificially inseminated. The mares were examined with ultrasound and inseminated with fresh semen in two consecutive cycles, control and treated, in a cross-over study design. The amount of intrauterine fluid was measured, and endometrial samples were collected 24 h after AI. The number of PMNs was determined by endometrial cytology and biopsy, and COX-2 labeling in endometrial samples was evaluated by immunohistochemistry. Firocoxib treatment did not induce ovulatory failure or affect embryo recovery rate in Experiment 1. In Experiment 2, firocoxib treatment reduced inflammation after AI in mares as evidenced with results regarding PMN numbers/percentage and endometrial COX-2 staining. In conclusion, the proposed treatment with firocoxib reduced endometrial inflammation in mares susceptible to PMIE after breeding, with no adverse effects.

Pharmacological Regulation in the USA and Pharmacokinetics Parameters of Firocoxib, a Highly Selective Cox-2, by Pain Management in Horses

The objective of the study was to conduct a review of the pharmacological regulation and pharmacokinetic parameters of firocoxib when administered orally or intravenously in horses. A search for literature was done in SCOPUS and PubMed for studies that had to evaluate the pharmacological regulation as well as the pharmacokinetic parameters of firocoxib when administered in horses. The nonsteroidal anti-inflammatory drugs have analgesic, anti-inflammatory, antipyretics, and antiendotoxic effects. The newly developed is selective to COX2 characterized by less adverse effects in veterinary patients when administered at the recommended doses and do not exceed the established prescribed time. Firocoxib is authorized by the Food and Drug Administration for the treatment of pain in horses, whereas for humans, there is still no approval. Controversy has arisen because the administration of the same pharmaceutical presentation in horses and dogs has pharmacokinetic differences between animal species. However, special attention must be paid to pharmacokinetic differences between species like in horses and dogs. In the case of the horse, the dosage is 0.1 mg/kg in single dose or up to 14 days in oral paste formulation and can keep maintained on the same concentration for a period of 7-14 days in oral tablet formulation. Thorough knowledge of pharmacological regulations and pharmacokinetic parameters, it allows the posology and effective application of firocoxib in pathologies associated with chronic pain, avoiding the indiscriminate use by owners and in some cases veterinarians, thus reducing the negative impacts on horse's health.

Effects of Firocoxib, Flunixin Meglumine, and Phenylbutazone on Platelet Function and Thromboxane Synthesis in Healthy Horses

OBJECTIVE

Determine the effects of nonsteroidal anti-inflammatory drugs (NSAID) on platelet function and thromboxane synthesis immediately after drug administration and following 5 days of NSAID administration in healthy horses.

STUDY DESIGN

Randomized cross-over study.

ANIMALS

Healthy adult horses (n=9; 6 geldings and 3 mares).

METHODS

Horses received either flunixin meglumine (1.1 mg/kg IV every 12 hours), phenylbutazone (2.2 mg/kg IV every 12 hours), or firocoxib (loading dose of 0.27 mg/kg IV on day 1, then 0.09 mg/kg IV every 24 hours for 4 days) for a total of 5 days. Blood samples were collected prior to drug administration (day 0), 1 hour after initial NSAID administration (day 1), and then 1 hour post-NSAID administration on day 5. Platelet function was assessed using turbidimetric aggregometry and a platelet function analyzer. Serum thromboxane B₂ concentrations were determined by commercial ELISA kit. A minimum 14 day washout period occurred between trials.

RESULTS

At 1 hour and 5 days postadministration of firocoxib, flunixin meglumine, or phenylbutazone, there was no significant effect on platelet aggregation or function using turbidimetric aggregometry or a platelet function analyzer. There was, however, a significant decrease in thromboxane synthesis at 1 hour and 5 days postadministration of flunixin meglumine and phenylbutazone that was not seen with firocoxib.

CONCLUSION

Preoperative administration of flunixin meglumine, phenylbutazone, or firocoxib should not inhibit platelet function based on our model. The clinical implications of decreased thromboxane B₂ synthesis following flunixin meglumine and phenylbutazone administration are undetermined.

Effect of firocoxib on cyclooxygenase 2, microsomal prostaglandin E2 synthase 1, and cytosolic phospholipase A2 gene expression in equine mononuclear cells

OBJECTIVE

To validate primer sets for use in reverse transcription quantitative PCR assays to measure gene expression of cytosolic phospholipase A2 (cPLA2) and microsomal prostaglandin E2 synthase 1 (mPGES1) in equine mononuclear cells and determine the effects of firocoxib, a selective cyclooxygenase 2 (COX-2) inhibitor, on COX-2, cPLA2, and mPGES1 gene expression following incubation of mononuclear cells with lipopolysaccharide (LPS).

ANIMALS

8 healthy adult horses.

PROCEDURES

Peripheral blood mononuclear cells were isolated by density gradient centrifugation and incubated at 37°C with medium alone, firocoxib (100 ng/mL), LPS (1 ng/mL or 1 μg/mL), or combinations of firocoxib and both LPS concentrations. After 4 hours, supernatants were collected and tested for prostaglandin E2 (PGE2) concentration with an enzyme inhibition assay, and gene expression in cell lysates was measured with PCR assays.

RESULTS

Primer pairs for cPLA2 and mPGES1 yielded single products on dissociation curve analyses, with mean assay efficiencies of 102% and 100%, respectively. Incubation with firocoxib and LPS significantly decreased PGE2 supernatant concentrations and significantly reduced COX-2 and mPGES1 gene expression, compared with values following incubation with LPS alone.

CONCLUSIONS AND CLINICAL RELEVANCE

Primer sets for mPGES1 and cPLA2 gene expression in equine mononuclear cells were successfully validated. Firocoxib significantly decreased LPS-induced COX-2 and mPGES1 expression, suggesting that it may be useful in the control of diseases in which expression of these genes is upregulated.

Efficacy of cyclo-oxygenase inhibition by two commercially available firocoxib products in horses

REASONS FOR PERFORMING STUDY

Two firocoxib preparations for oral use are approved for use in animals in many countries: a chewable canine tablet and an equine paste. In order to reduce costs, many veterinarians use the canine product in horses even though this is an off-label use of the preparation.

OBJECTIVE

To determine the relative efficacy of 2 commercially available firocoxib products to inhibit prostaglandin E₂ (PGE2) synthesis after oral dosing in horses.

STUDY DESIGN

A crossover design using 8 adult horses (n = 4 for each preparation during each treatment period). Body weight range 532-614 kg.

METHODS

Horses received 57 mg of the assigned firocoxib preparation orally once daily for 7 days, with a 14 day washout period between drug crossover. Ten healthy adult light breed horses were used as no-treatment controls. During each treatment period, blood was taken before dosing on Days 0 and 7 and on Day 7 1 h after dosing for ex vivo lipopolysaccharide (LPS) stimulation to induce (PGE₂ ) synthesis. Heparinised plasma was also collected on Day 7 immediately prior to and 1 h after dosing to determine plasma firocoxib concentrations.

RESULTS

In the control group, there was no significant change in LPS-induced PGE2 over time. In contrast, immediately prior to and 1 h after treatment on Day 7, the mean LPS-induced PGE₂ concentration decreased significantly compared to Day 0 values in all treated horses. There was no difference in PGE₂ or plasma firocoxib concentrations between firocoxib treatment groups.

CONCLUSION

In this model, the canine chewable preparation of firocoxib was as effective as the equine paste formulation at reducing LPS-induced PGE₂ synthesis.

POTENTIAL RELEVANCE

The canine chewable preparation of firocoxib may be a suitable alternative to the paste formulation in horses for situations where extra-label drug use can be legally justified. The Summary is available in Chinese - see Supporting information.

Src/NF-κB-targeted inhibition of LPS-induced macrophage activation and dextran sodium sulphate-induced colitis by Archidendron clypearia methanol extract

ETHNOPHARMACOLOGICAL RELEVANCE

Archidendron clypearia Jack. (Fabaceae) has been traditionally used to treat various inflammatory diseases such as pain in the eyes. However, the antiinflammatory mechanism of A. clypearia has not been fully elucidated. This study examined the anti-inflammatory mechanism of a 95% methanol extract (Ac-ME) of A. clypearia in vitro and in vivo.

MATERIALS AND METHODS

The effect of Ac-ME on the production of inflammatory mediators in RAW264.7 cells and peritoneal macrophages and on symptoms of colitis in mouse induced by dextran sodium sulphate (DSS) was investigated. Molecular mechanisms underlying the inhibitory effects were elucidated by analyzing the activation of transcription factors and their upstream signaling as well as by evaluating the kinase activity of target enzymes in vitro and in vivo.

RESULTS

Ac-ME dose-dependently suppressed the secretion of nitric oxide (NO) and prostaglandin (PG)E₂ from RAW264.7 cells and peritoneal macrophages stimulated by lipopolysaccharide (LPS). Ac-ME clearly reduced mRNA expression of inducible NO synthase (iNOS), cyclooxygenase (COX)-2, and tumor necrosis factor (TNF)-α by the blockade of nuclear factor (NF)-κB activation and its upstream signaling events containing protein tyrosine kinase such as Syk and Src. In agreement with this, Ac-ME directly reduced the kinase activities of Src and Syk as well as the formation of molecular signaling complex including p85. DSS-induced colitis was also remarkably inhibited by this extract through the suppression of Src and IκBα phosphorylation.

CONCLUSION

Ac-ME displays strong anti-inflammatory activity in vivo by suppressing Src/Syk-mediated NF-κB activation which is linked to its ethno-pharmacological uses as an anti-gastritis remedy. Through preclinical studies, the potential therapeutic application will be tested further.

A randomised, double-blinded, placebo-controlled study on the efficacy of a unique extract of green-lipped mussel (Perna canaliculus) in horses with chronic fetlock lameness attributed to osteoarthritis

REASONS FOR PERFORMING STUDY

Lyophilised products from green-lipped mussel (Perna canaliculus[LPPC]) are used to orally treat horses with osteoarthritis (OA). However, no randomised, controlled or double-blinded studies on the efficacy of this treatment in horses have been reported to date.

OBJECTIVE

To investigate the effects of a unique LPPC (Biolane)(1) in improving clinical signs of OA in the fetlock.

METHODS

Data were analysed from 26 horses with primary fetlock lameness in a controlled, randomised and double-blinded, multi-centre clinical trial. The study design was a partial crossover with a washout period and consisted of 19 horses treated with LPPC and 20 with a placebo. Horses were dosed orally with 25 mg/kg bwt/day LPPC or placebo for 56 days. Efficacy was evaluated by clinical assessment of lameness, passive flexion, pain, swelling and heat in the affected joint. Relationships between variables were analysed using an ordinal logistic model with random effects for horse and horse x treatment according to a modified intention-to-treat analysis.

RESULTS

Clinical evaluation of horses with a fetlock lameness treated with LPPC showed a significant reduction in severity of lameness (P<0.001), improved response to the joint flexion test (P<0.001) and reduced joint pain (P = 0.014) when compared with horses treated with placebo.

CONCLUSIONS

The LPPC significantly alleviated the severity of lameness and joint pain and improved response to joint flexion in horses with lameness attributable to OA in the fetlock.