Effects of the cyclooxygenase inhibitor meloxicam on recovery of ischemia-injured equine jejunum

Comparison of the Inhibitory Effects of Flunixin Meglumine and Meloxicam on the Smooth Muscles Motility of the Gastrointestinal Tract of Cattle

This study aimed to compare the inhibitory effect of flunixin meglumine and meloxicam on the smooth muscles of the gastrointestinal tract in male cattle. Tissue samples, including the abomasum, ileum, proximal loop and centripetal gyri of the ascending colon, were collected from routinely slaughtered male cattle. These samples were sectioned into strips and mounted in an isolated tissue bath system. Smooth muscle contractions were evoked using carbachol, and cumulative doses of atropine, flunixin meglumine and meloxicam were administered to assess smooth muscle activity. Atropine, used as a positive control, did not abolish contractions in the abomasum and centripetal gyri tissues, even at a high concentration of 10 µM. Based on area-under-curve values, flunixin meglumine demonstrated a greater inhibitory effect than meloxicam by factors of 8.57, 4.28, 12.44 and 3.93 in the abomasum, ileum, proximal loop and centripetal gyri tissues, respectively. For beats-per-minute values, flunixin meglumine exhibited a stronger inhibitory effect than meloxicam by factors of 7.22, 3.88, 7.03 and 3.35 in the abomasum, ileum, proximal loop and centripetal gyri tissues, respectively. Finally, based on peak maximum values, flunixin meglumine's inhibitory effect was 6.13, 4.43, 7.07 and 7.02 times greater than that of meloxicam in the abomasum, ileum, proximal loop and centripetal gyri tissues, respectively. In conclusion, flunixin meglumine was more potent than meloxicam in inhibiting smooth muscle activity. Conversely, meloxicam is associated with fewer adverse effects due to its selective action on the cyclooxygenase-2 enzyme. However, flunixin meglumine may be more advantageous than meloxicam for applications in beef and milk production due to its shorter residue elimination time.

Pharmacokinetics of Meloxicam in Different Animal Species: A Comprehensive Review

Meloxicam is a non-steroidal anti-inflammatory in the oxicam group. It has been extensively used in human and veterinary medicine for their anti-inflammatory, analgesic and antipyretic activities. Meloxicam has shown high therapeutic potential for disorders such as osteoarthritis, musculoskeletal disorder, acute respiratory infection, puerperal septicemia, mastitis and mastitis-metritis-agalactia syndrome. Although meloxicam pharmacokinetic has been described for numerous species, no paper summarizes the existing literature on this field. Thus, the aim of this review was to carry out a review of the literature on the pharmacokinetics of meloxicam in different animal species and gather the data in a single review article. A comprehensive review of the available literature in the PubMed, Web of Science and Scopus databases was performed. Meloxicam shows good bioavailability after oral and parenteral administration in most animal species (85-95%), with the lowest values in sheep after oral administration. It presents a rapid distribution with a small volume of distribution, which can be attributed to relatively high ionization state of meloxicam at physiological pH and its high plasma protein binding (close to 99%). It is extensively metabolized in the liver in several inactive polar metabolites, which are excreted, like unchanged meloxicam in urine and feces. Meloxicam also shows a long elimination half-life and low clearance.

Pharmacologic Interventions to Immunologic and Immune-Mediated Conditions in Horses

Immunomodulators can stimulate, suppress, or regulate one or many aspects of the immune response. Use of a variety of immunostimulants, immunosuppressors, and anti-inflammatory drugs are described in horses, but the evidence supporting their efficacy is variable. Corticosteroids and nonsteroidal anti-inflammatory drugs are the best characterized immunomodulators in horses, but further study is needed to fully define their ideal dosing protocols and indications and to characterize the efficacy of other immunomodulators in equine medicine.

Analgesic Efficacy of Non-Steroidal Anti-Inflammatory Drug Therapy in Horses with Abdominal Pain: A Systematic Review

This systematic review aimed to identify the evidence concerning the analgesic efficacy of non-steroidal anti-inflammatory drugs to treat abdominal pain in horses, and to establish whether one non-steroidal anti-inflammatory drug could provide better analgesia compared to others. This systematic review was conducted following the "Systematic Review Protocol for Animal Intervention Studies". Research published between 1985 and the end of May 2023 was searched, using three databases, namely, PubMed, Embase, and Scopus, using the words equine OR horse AND colic OR abdominal pain AND non-steroidal anti-inflammatory drug AND meloxicam OR flunixin meglumine OR phenylbutazone OR firocoxib OR ketoprofen. Risk of bias was assessed with the SYRCLE risk of bias tool, and level of evidence scored according to the Oxford Centre for Evidence-based Medicine. A total of 10 studies met the inclusion criteria. From those only one study judged pain with a validated pain score, and a high risk of bias was identified due to the presence of selection, performance, and "other" types of bias. Therefore, caution is required in the interpretation of results from individual studies. To date, the evidence on analgesic efficacy to determine whether one drug is more potent than another regarding the treatment of abdominal pain in horses is sparse.

Effect of Firocoxib and Flunixin Meglumine on Large Colon Mural Thickness of Healthy Horses

Nonsteroidal anti-inflammatory drug (NSAID) administration carries risks of gastrointestinal toxicity. Selective COX-2 inhibitors ("coxibs") were designed to reduce risks of adverse effects but are still associated with gastrointestinal complications in humans. The effect of coxibs on colonic inflammation and integrity in horses is unknown. The study objective was to compare the effects of the coxib firocoxib and the nonselective NSAID flunixin meglumine on ultrasonographic indicators of colonic inflammation in healthy horses. Twelve healthy adult horses were administered flunixin meglumine (1.1 mg/kg IV q12h) and omeprazole (1 mg/kg PO q24h) for 5 days, allowed a 6-month washout period, then administered firocoxib (0.3 mg/kg PO once, then 0.1 mg/kg PO q24h for 4 days) and omeprazole. Transabdominal ultrasonographic examination and serum chemistry profiles were performed at the beginning and end of each treatment week. Colon wall thickness increased over time when horses received firocoxib (median post treatment 5.8 mm, interquartile range 2.8 mm; P < .001), but not flunixin (median 3 mm, interquartile range 1.2 mm; P = .7) and was significantly greater following firocoxib compared to flunixin (P = .003). Subjectively, colonic edema was noted more frequently following treatment with firocoxib (11/12 horses), compared to flunixin (1/12 horses). There were no clinically significant alterations in hematologic parameters after administration of either drug. The increase in colon wall thickness following treatment with the COX-2 selective NSAID firocoxib may suggest a risk of subclinical colitis in healthy horses. Monitoring colonic health when NSAIDs are used in a clinical setting is warranted.

Non-Steroidal Anti-Inflammatory Drugs and Associated Toxicities in Horses

Effective pain management in horses can be a challenge despite the understanding that appropriate analgesia improves animal welfare and increases treatment success. The administration of NSAID drugs, particularly phenylbutazone and flunixin, are common practice in equine veterinary patients. Known for their analgesic and anti-inflammatory properties, NSAIDs are used for the treatment of a variety of conditions in horses, from gastrointestinal to orthopedic pain. Despite extensive usage, NSAIDs have a narrow margin of safety and the body of literature documenting the efficacy and side effects of different NSAIDs is broad. The three main side effects associated with excessive or prolonged NSAID usage in horses include gastroduodenal ulceration, right dorsal colitis (RDC) and renal papillary necrosis. The use of cyclooxygenase-2 selective NSAIDS, such as firocoxib, are theoretically safer. The aim of this paper is to review the current literature on the use and efficacy of different NSAIDs, summarise the associated side effects of NSAID usage and evaluate the current state of knowledge for the diagnosis and treatment of such toxicities.

Comparison of Flunixin Meglumine, Meloxicam and Ketoprofen on Mild Visceral Post-Operative Pain in Horses

Simple Summary

Pain management following surgical intervention is key. In horses, several anti-inflammatories (flunixin meglumine, meloxicam and ketoprofen) are available for the management of pain following castration. However, their analgesic efficacy remains unclear for mild visceral pain. The aim of this study was to compare the analgesic efficacy of the above-mentioned anti-inflammatory drugs, following a simple surgery (inguinal castration). Horses were administered a randomly assigned anti-inflammatory drug before and after surgery. A pain score was recorded using a previously described pain assessment scale (PASPAS) before administration, and after the first and second administrations by a senior clinician and a veterinary student. Thirty horses were evaluated, and there was no significant effect of the drug administered on the pain score. Horse welfare was not compromised regardless of drug assigned. Horses showed mild pain post-operatively, which decreased significantly within 24 h. Pain scores were significantly different when assessed by a veterinary student and a senior clinician. The authors found that the anti-inflammatory drug studied provided a similar level of analgesia for the management of mild visceral pain in horses, but that the pain scale used is not suitable for junior evaluators or, by extension, owners.

Abstract

The analgesic efficacy of meloxicam and ketoprofen against equine visceral pain is unclear. The aim of this study was to compare the analgesic efficacy of meloxicam (M) and ketoprofen (K) to flunixin meglumine (F) following inguinal castration. Horses undergoing inguinal castration under general anesthesia were randomly assigned F (1.1 mg/kg), M (0.6 mg/kg) or K (2.2 mg/kg) intravenously two hours pre-operatively and 24 h later. A pain score (out of 31) was recorded blindly by a senior clinician and veterinary student before NSAIDs administration (T₀), and after the first (T₁) and second (T₂) administrations, using a modified post-abdominal surgery pain assessment scale (PASPAS). Pain was classified as mild (score ≤ 7), moderate (score = 8–14) or severe (score > 14). Thirty horses (12 F, 10 M, 8 K) aged 6.2 ± 4.9 years, mostly warmbloods, were included. Horse welfare was not compromised regardless of the drug assigned. There was no statistically significant effect of NSAIDs on pain score. Mean pain scores were significantly higher at T₁ than T₀ for each NSAID (F: 5.08 ± 2.50 vs. 1.58 ± 1.38 (p < 0.001); M: 4.60 ± 2.32 vs. 1.10 ± 1.20 (p < 0.001); K: 5.25 ± 1.39 vs. 1.50 ± 1.51 (p < 0.0001)) and lower at T₂ than T₁ for F (2.92 ± 2.423 vs. 5.08 ± 2.50 (p < 0.001)) and M (2.90 ± 1.37 vs. 4.60 ± 2.32 (p < 0.0325)). At T₁, senior pain scores were significantly different than for junior (5.56 ± 0.54 vs. 3.22 ± 0.62, p = 0.005). This study indicates that meloxicam and ketoprofen provide a similar level of analgesia to flunixin meglumine for the management of mild visceral pain in horses. PASPAS is not reliable for junior evaluators.

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.

Effect of body condition on intestinal permeability in horses

OBJECTIVE

To investigate effects of body condition on permeability of intestinal mucosa in horses.

ANIMALS

13 horses (7 obese and 6 lean) from 8 to 15 years of age.

PROCEDURES

Body condition score was assessed, and an oral sugar test (OST) was performed to evaluate glucose and insulin dynamics. Horses were allowed a 2-week diet acclimation period and were then euthanized. Tissue samples were collected from the jejunum, ileum, cecum, pelvic flexure, right dorsal colon, and rectum. Mucosal permeability was assessed by measuring transepithelial resistance and lipopolysaccharide (LPS) flux across tissue samples mounted in Ussing chambers.

RESULTS

5 obese horses and 1 lean horse had evidence of insulin dysregulation, whereas 1 obese and 5 lean horses had no abnormalities in results of the OST. Results for the OST were not available for 1 obese horse. Mucosal transepithelial resistance did not differ in any intestinal segment between obese and lean horses. Obese horses had a significantly higher LPS flux across jejunal mucosa, compared with results for lean horses, but there were no significant differences between obese and lean horses for other intestinal segments.

CONCLUSIONS AND CLINICAL RELEVANCE

Obese horses may have had greater paracellular mucosal permeability of jejunal mucosa to LPS, compared with that for lean horses. This finding was consistent with data for the gastrointestinal mucosa of humans and mice and supported the hypothesis that obese horses may be at higher risk from chronic exposure to increased amounts of LPS, compared with the risk for lean horses.

Sparing the gut: COX-2 inhibitors herald a new era for treatment of horses with surgical colic

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used to manage a wide variety of conditions in horses, including management of colic. Flunixin meglumine is by far the most commonly used drug in the control of colic pain and inflammation and has become a go-to for not only veterinarians but also horse-owners and nonmedical equine professionals. NSAID use, however, has always been controversial in critical cases due to a high risk of adverse effects associated with their potent cyclo-oxygenase (COX) inhibition. There are two important COX isoenzymes: COX-1 is generally beneficial for normal renal and gastrointestinal functions and COX-2 is associated with the pain and inflammation of disease. Newer selective NSAIDs can target COX-2-driven pathology while sparing important COX-1-driven physiology, which is of critical importance in horses with severe gastrointestinal disease. Emerging research suggests that firocoxib, a COX-2-selective NSAID labelled for use in horses, may be preferable for use in colic cases in spite of the decades-long dogma that flunixin saves lives.

Oral Administration of Meloxicam Suppresses Low-Dose Endotoxin Challenge-Induced Pain in Thoroughbred Horses

Nonsteroidal anti-inflammatory drugs such as flunixin meglumine have been used to treat signs of systemic inflammatory conditions, but it is also known to have the side effect to small intestine mucosa. It may be considered to be due to inhibition of both cyclooxygenase (COX)-1 and COX-2. On the other hand, meloxicam is widely used in equine clinical practice and an effective nonsteroidal anti-inflammatory drug with the preferential inhibitory effect on COX-2. However, it has not yet been evaluated in equine systemic inflammation. The aim of this study was to evaluate the effect of meloxicam administered 60 minutes prior lipopolysaccharide (LPS)-induced inflammatory response in five Thoroughbred horses using a crossover test. Clinical parameters including body temperature, heart rate, respiratory rate, behavioral pain score, and hoof wall surface temperature were recorded, and plasma tumor necrosis factor-alpha, cortisol, and leukocyte counts were measured at various times before and after LPS infusion for 420 minutes. At time points 60, 90 (P < .01), 120, and 180 (P < .05) minutes, pain scores were significantly lower in meloxicam-treated horses. There was no significant difference in other parameters. In the present study, we revealed the analgesic effect of meloxicam using an equine low-dose endotoxin model.

Pharmacokinetics of meloxicam after oral administration of a granule formulation to healthy horses

Background

Nonsteroidal anti‐inflammatory drugs are administered in horses for several systemic diseases. Selective cyclooxygenase‐2 inhibitors are preferred because of lower risk of adverse effects. Several meloxicam formulations have been tested in horses, but a recently marketed granule oral formulation has not been studied.

Objective

To characterize the pharmacokinetics of a novel granule meloxicam formulation in fasted and fed horses, and to compare pharmacokinetic features with oral suspension and tablets.

Animals

Seven healthy adult horses.

Methods

Meloxicam was administered at 0.6 mg/kg in fasted or fed horses. Blood samples were collected for pharmacokinetic analysis, and vital signs, hematology, and biochemistry variables were monitored for 72 hours.

Results

No adverse effects were detected. Volume of distribution and clearance after intravenous administration of meloxicam were 0.36 L/kg and 29.12 mL/h/kg, respectively, with a 12.39 hours of terminal half‐life. Protein binding was of 97%. Bioavailability was high for every oral formulation, ranging 70%‐110%, without feed effect. Because of a slower absorption, meloxicam after administration of granules had a longer half‐life (24 and 34 hours, fasted and fed, respectively) and mean residence time (31 and 47 hours), than suspension and tablets (ranging 10‐13 and 13‐15 hours, respectively). In addition, the time above therapeutic concentration was higher for the granule formulation than other formulations.

Conclusions and Clinical Importance

Granule formulation has different PK parameters compared to other oral formulations, which could enable this formulation to be used for different dosage regimens in order to reach a desired clinical effect or decrease the risk of adverse effects.

Multicentre, blinded, randomised clinical trial comparing the use of flunixin meglumine with firocoxib in horses with small intestinal strangulating obstruction

BACKGROUND

Small intestinal strangulating obstruction (SISO) is associated with endotoxaemia which leads to an increased risk of death. Nonsteroidal anti-inflammatory drugs (NSAIDs) are used to treat signs of endotoxaemia by inhibiting cyclo-oxygenases (COX). COX-1 is expressed constitutively and promotes gut barrier function, whereas COX-2 is inducible and contributes to the signs of endotoxaemia. In preclinical SISO trials, intestinal barrier recovery was more complete with reductions in endotoxin permeability in horses treated with COX-2 selective NSAIDs as compared with horses treated with flunixin meglumine.

OBJECTIVES

We hypothesised that treatment of post-surgical SISO horses with firocoxib (COX-2 selective) would reduce the signs of endotoxaemia to a greater extent than flunixin meglumine (nonselective COX inhibitor) while continuing to provide similar levels of pain control.

STUDY DESIGN

Blinded randomised clinical trial.

METHODS

In addition to clinical monitoring, preoperative and 12-, 24- and 48-h post-operative plasma samples were assessed for prostaglandin E₂ (PGE₂ ), thromboxane B₂ (TXB₂ ), TNF⍺ and soluble CD14 (sCD14).

RESULTS

In 56 recruited SISO horses, either flunixin meglumine (1.1 mg/kg, i.v., q12h) or firocoxib (0.3 mg/kg, i.v. loading dose; 0.1 mg/kg, i.v., q24h) was given in the post-operative period in three university hospitals from 2015 to 2017. COX-2 selectivity was confirmed by a relative lack of inhibition of the COX-1 prostanoid TXB₂ by firocoxib and significant inhibition by flunixin meglumine (P = 0.014). Both drugs inhibited the COX-2 prostanoid PGE₂ . There were no significant differences in pain scores between groups (P = 0.2). However, there was a 3.23-fold increased risk (P = 0.04) of increased plasma sCD14 in horses treated with flunixin meglumine, a validated biomarker of equine endotoxaemia.

MAIN LIMITATIONS

Horses were all treated with flunixin meglumine prior to referral. In addition, many horses were treated with lidocaine, which has been shown to mitigate the deleterious effects of flunixin meglumine.

CONCLUSIONS

In SISO cases, firocoxib reduced a biomarker of endotoxaemia as compared with flunixin meglumine while continuing to provide similar levels of pain control.

Scalable Gastric Resident Systems for Veterinary Application

Gastric resident dosage forms have been used successfully in farm animals for the delivery of a variety of drugs helping address the challenge of extended dosing. Despite these advances, there remains a significant challenge across the range of species with large variation in body size. To address this, we investigate a scalable gastric resident platform capable of prolonged retention. We investigate prototypes in dimensions consistent with administration and retention in the stomachs of two species (rabbit and pig). We investigate sustained gastric retention of our scalable dosage form platform, and in pigs show the capacity to modulate drug release kinetics of a model drug in veterinary practice, meloxicam, with our dosage form. The ability to achieve gastric residence and thereby enable sustained drug levels across different species may have a significant impact in the welfare of animals in both research, agricultural, zoological, and clinical practice settings.

Advances in Diagnostics and Treatments in Horses with Acute Colic and Postoperative Ileus

Differentiating between medical and surgical causes of colic is one of the primary goals of the colic workup, because early surgical intervention improves prognosis in horses requiring surgery. Despite the increasing availability of advanced diagnostics (hematologic analyses, abdominal ultrasound imaging, etc), the most accurate indicators of the need for surgery remain the presence of moderate to severe signs of abdominal pain, recurrence of pain after appropriate analgesic therapy, and the absence of intestinal borborygmi. Investigation of novel biomarkers, which may help to differentiate surgical lesions from those that can be managed medically, continues to be an active area of research.

Equine Intestinal Mucosal Pathobiology

The equine intestinal mucosa is intimately involved in maintaining homeostasis both on a systemic level by controlling extracellular fluid movement and at the local level to maintain barrier function. Horses are particularly susceptible to the clinical syndrome of colic, with the most severe cases involving strangulating obstruction that induces ischemia. Because of the mucosal vascular architecture, the mucosal epithelium is particularly susceptible to ischemic injury. The potential for reperfusion injury has been investigated and found to play a minimal role. However, inflammation does affect mucosal repair. Mechanisms of repair, including villus contraction, epithelial restitution, and tight junction closure, are critical to reforming the mucosal barrier. Nonsteroidal anti-inflammatory drugs have an impact on this repair, particularly at the level of the tight junctions. Completion of mucosal regeneration requires proliferation, which is now being actively studied in equine enteroids. All of these aspects of equine mucosal pathobiology are reviewed in depth.

Update on the use of cyclooxygenase-2-selective nonsteroidal anti-inflammatory drugs in horses

Nonsteroidal anti-inflammatory drugs work through inhibition of cyclooxygenase (COX) and are highly effective for the treatment of pain and inflammation in horses. There are 2 clinically relevant isoforms of COX. Cyclooxygenase-1 is constitutively expressed and is considered important for a variety of physiologic functions, including gastrointestinal homeostasis. Thus, NSAIDs that selectively inhibit COX-2 while sparing COX-1 may be associated with a lower incidence of adverse gastrointestinal effects. Various formulations of firocoxib, a COX-2-selective NSAID, labeled for use in horses are available in the United States. Equine practitioners should know that the FDA limits the use of firocoxib to formulations labeled for horses, regardless of price concerns. In addition, practitioners will benefit from understanding the nuances of firocoxib administration, including the importance of correct dosing and the contraindications of combining NSAIDs. Together with knowledge of the potential advantages of COX-2 selectivity, these considerations will help veterinarians select and treat patients that could benefit from this new class of NSAID.

Treatment of meloxicam overdose in a dog via therapeutic plasma exchange

OBJECTIVE

To describe the treatment of a meloxicam overdose in a dog with therapeutic plasma exchange (TPE).

CASE SUMMARY

A 6-month-old female Bulldog, presented for routine laparoscopic ovariectomy. Postoperatively the dog received an accidental overdose of meloxicam (1 mg/kg IV [intravenously]). The patient was treated with supportive medical therapy and TPE over 210 minutes achieving 1.2 plasma volume exchanges. During therapy, heparinized blood and effluent samples were collected. Meloxicam concentrations were determined in the samples by high pressure liquid chromatography. Post TPE, the dog continued to receive supportive medical therapy and was discharged 48 hours after the overdose. The dog remained asymptomatic for meloxicam intoxication. Follow-up rechecks at 1 and 6 weeks were unremarkable with no further treatment required.

NEW OR UNIQUE INFORMATION

This report describes the successful use of TPE adjunctively following an acute meloxicam overdose. An 82% reduction of plasma meloxicam concentration was achieved over 210 minutes. Twenty-four hours after therapy, a 47% sustained reduction of plasma meloxicam was measured after redistribution of drug between body compartments.

Treatment of endotoxaemia and septicaemia in the equine patient

Endotoxins, constituents of the cell wall of gram-positive and gram-negative bacteria, regularly result in severe illness and death in horses. In endotoxaemia, these constituents are present in the systemic circulation; in septicaemia, whole microbes invade normally sterile parts of the body. Interaction of these endotoxins with pathogen recognition receptors leads to an inflammatory response that cannot always be sufficiently contained and hence needs direct treatment. Over the last decennia, our understanding of the pathophysiology of endotoxaemia and septicaemia has significantly increased. Based on improved understanding of the interaction between receptors and endotoxins as well as the subsequent downstream signalling pathways, new therapeutic targets have been identified in laboratory animal species and humans. Important species differences in the recognition of endotoxins and pathogens by their receptors as well as the inflammatory response to receptor activation hamper extrapolation of this information to the horse (and other species). Historically, horses with endotoxaemia and septicaemia have been treated mainly symptomatically and supportively. Based on the identified therapeutic targets, this review describes the current knowledge of the treatment for endotoxaemia and septicaemia in the horse with reference to the findings in other animal species and humans.

Inhibition of Kv channel expression by NSAIDs depolarizes membrane potential and inhibits cell migration by disrupting calpain signaling

Clinical use of non-steroidal anti-inflammatory drugs (NSAIDs) is well known to cause gastrointestinal ulcer formation via several mechanisms that include inhibiting epithelial cell migration and mucosal restitution. The drug-affected signaling pathways that contribute to inhibition of migration by NSAIDs are poorly understood, though previous studies have shown that NSAIDs depolarize membrane potential and suppress expression of calpain proteases and voltage-gated potassium (Kv) channel subunits. Kv channels play significant roles in cell migration and are targets of NSAID activity in white blood cells, but the specific functional effects of NSAID-induced changes in Kv channel expression, particularly on cell migration, are unknown in intestinal epithelial cells. Accordingly, we investigated the effects of NSAIDs on expression of Kv1.3, 1.4, and 1.6 in vitro and/or in vivo and evaluated the functional significance of loss of Kv subunit expression. Indomethacin or NS-398 reduced total and plasma membrane protein expression of Kv1.3 in cultured intestinal epithelial cells (IEC-6). Additionally, depolarization of membrane potential with margatoxin (MgTx), 40mM K(+), or silencing of Kv channel expression with siRNA significantly reduced IEC-6 cell migration and disrupted calpain activity. Furthermore, in rat small intestinal epithelia, indomethacin and NS-398 had significant, yet distinct, effects on gene and protein expression of Kv1.3, 1.4, or 1.6, suggesting that these may be clinically relevant targets. Our results show that inhibition of epithelial cell migration by NSAIDs is associated with decreased expression of Kv channel subunits, and provide a mechanism through which NSAIDs inhibit cell migration and may contribute to NSAID-induced gastrointestinal (GI) toxicity.

Prevention of post operative complications following surgical treatment of equine colic: Current evidence

Changes in management of the surgical colic patient over the last 30 years have resulted in considerable improvement in post operative survival rates. However, post operative complications remain common and these impact negatively on horse welfare, probability of survival, return to previous use and the costs of treatment. Multiple studies have investigated risk factors for post operative complications following surgical management of colic and interventions that might be effective in reducing the likelihood of these occurring. The findings from these studies are frequently contradictory and the evidence for many interventions is lacking or inconclusive. This review discusses the current available evidence and identifies areas where further studies are necessary and factors that should be taken into consideration in study design.

The use of nonsteroidal anti-inflammatory drugs in critically ill horses

OBJECTIVE

To review the physiology of the cyclooxygenase (COX) enzymes with reference to the beneficial effects of nonsteroidal anti-inflammatory drugs (NSAIDs) related to their analgesic and antiendotoxic properties as well as the mechanisms responsible for adverse gastrointestinal, renal, and coagulation effects.

DATA SOURCES

Human and veterinary peer reviewed literature

VETERINARY DATA SYNTHESIS

NSAIDs are frequently administered to critically ill horses for their analgesic and anti-inflammatory effects. However, NSAIDs have significant side effects principally on the gastrointestinal mucosa and kidneys. These side effects may be exacerbated in critically ill horses if they have gastrointestinal damage or are volume depleted

CONCLUSIONS

This review provides important information for equine veterinarians and criticalists on the advantages and disadvantages of using traditional NSAIDs and newer equine COX-2 selective NSAIDs for the management of different conditions in critically ill horses.

Pharmacokinetics and adverse effects of oral meloxicam tablets in healthy adult horses

The objective of this study was to assess the pharmacokinetic profile and determine whether any adverse effects would occur in seven healthy adult horses following oral meloxicam tablet administration once daily for 14 days at a dose of 0.6 mg/kg·bwt. Horses were evaluated for health using physical examination, complete blood count, serum chemistry, urinalysis, and gastroscopy at the beginning and end of the study. Blood was collected for the quantification of meloxicam concentrations with liquid chromatography and mass spectrometry. The mean terminal half-life was 4.99 ± 1.11 h. There was no significant difference between the mean Cmax , 1.58 ± 0.71 ng/mL at Tmax 3.48 ± 3.30 h on day 1, 2.07 ± 0.94 ng/mL at Tmax 1.24 ± 1.24 h on day 7, and 1.81 ± 0.76 ng/mL at 1.93 ± 1.30 h on day 14 (P = 0.30). There was a statistically significant difference between the Tmax on the sample days (P = 0.04). No statistically significant increase in gastric ulcer score or laboratory analytes was noted. Oral meloxicam tablets were absorbed in adult horses, and adverse effects were not statistically significant in this study. Further studies should evaluate the adverse effects and efficacy of meloxicam tablets in a larger population of horses before routine use can be recommended.

The effect of nonsteroidal anti-inflammatory drugs on the equine intestine

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used in the management of pain and endotoxaemia associated with colic in the horse. While NSAIDs effectively treat the symptoms of colic, there is evidence to suggest that their administration is associated with adverse gastrointestinal effects including right dorsal colitis and inhibition of mucosal barrier healing. Several studies have examined the pathophysiology of NSAID associated effects on the large and small intestine in an effort to avoid these complications and identify effective alternative medications. Differences in the response of the large and small intestines to injury and NSAID treatment have been identified. Flunixin meglumine has been shown in the small intestine to inhibit barrier function recovery and increase permeability to lipopolysaccharide (LPS). A range of NSAIDs has been examined in the small intestine and experimental evidence suggests that those NSAIDs with cyclooxygenase independent anti-inflammatory effects or a COX-2 selective mode of action may offer significant advantages over traditional NSAIDs.

Ischemic postconditioning does not attenuate ischemia-reperfusion injury of rabbit small intestine

OBJECTIVE

To determine whether ischemic postconditioning can attenuate intestinal ischemia-reperfusion (I-R) injury and has a beneficial effect on tissue blood flow during reperfusion.

STUDY DESIGN

In vivo experimental study.

ANIMALS

New Zealand White rabbits (n=6).

METHODS

Rabbits were anesthetized with pentobarbital, to avoid the preconditioning effects of volatile anesthetics, and ventilated with room air. Rectal temperature, hemodynamics, and normocapnia were maintained. After celiotomy, 3 jejunal segments were isolated in each rabbit for the following groups: (1) control, (2) I-R, and (3) I-R with postconditioning. I-R was induced by a 45-minute occlusion of the segment jejunal artery followed by 2-hour reperfusion. The postconditioning segment had 4 cycles of 30-second reperfusion and 30-second reocclusion during the initial 4 minutes of reperfusion. Stable isotope-labeled microspheres were used to measure intestinal blood flow at baseline, end occlusion, and end reperfusion. At the end of reperfusion, intestine segments were harvested and the rabbits euthanatized. A semiquantitative histopathologic evaluation (0-5) was conducted by a single, blinded observer. Wet-to-dry weight ratios were calculated to assess intestinal edema.

RESULTS

There was no significant difference in grade of necrosis, tissue wet-to-dry weight ratios, or blood flow at any time point between ischemic and postconditioning groups.

CONCLUSIONS

Ischemic postconditioning was ineffective in this model of intestinal I-R.

CLINICAL RELEVANCE

Further experimental studies will need to be performed before clinical application of postconditioning for intestinal ischemia.

Expression of cyclooxygenase-1 and -2 in the left dorsal colon after different durations of ischemia and reperfusion in horses

OBJECTIVE-To identify expression and localization of cyclooxygenase (COX)-1 and COX-2 in healthy and ischemic-injured left dorsal colon of horses. SAMPLE POPULATION-Left dorsal colon tissue samples from 40 horses. PROCEDURES-Tissue samples that were used in several related studies on ischemia and reperfusion were evaluated. Samples were collected during anesthesia, before induction of ischemia, and following 1 hour of ischemia, 1 hour of ischemia and 30 minutes of reperfusion, 2 hours of ischemia, 2 hours of ischemia and 30 minutes of reperfusion, and 2 hours of ischemia and 18 hours of reperfusion. Histomorphometric analyses were performed to characterize morphological injury. Immunohistochemical analyses were performed to characterize expression and localization of COX-1 and COX-2. RESULTS-COX-1 and COX-2 were expressed in control tissues before ischemia was induced, predominantly in cells in the lamina propria. Ischemic injury significantly increased expression of COX-2 in epithelial cells on the colonic surface and in crypts. A similar significant increase of COX-1 expression was seen in the epithelial cells. CONCLUSIONS AND CLINICAL RELEVANCE-On the basis of information on the role of COX-2, upregulation of COX-2 in surface epithelium and crypt cells following ischemic injury in equine colon may represent an early step in the repair process.

Effect of firocoxib or flunixin meglumine on recovery of ischemic-injured equine jejunum

OBJECTIVE

To determine whether treatment of horses with firocoxib affects recovery of ischemic-injured jejunum, while providing effective analgesia.

ANIMALS

18 horses.

PROCEDURES

Horses (n = 6 horses/group) received saline (0.9% NaCl) solution (1 mL/50 kg, IV), flunixin meglumine (1.1 mg/kg, IV, q 12 h), or firocoxib (0.09 mg/kg, IV, q 24 h) before 2 hours of jejunal ischemia. Horses were monitored via pain scores and received butorphanol for analgesia. After 18 hours, ischemic-injured and control mucosa were placed in Ussing chambers for measurement of transepithelial resistance and permeability to lipopolysaccharide. Histomorphometry was used to determine denuded villus surface area. Western blots for cyclooxygenase (COX)-1 and COX-2 were performed. Plasma thromboxane B(2) and prostaglandin E(2) metabolite (PGEM) concentrations were determined.

RESULTS

Pain scores did not significantly increase after surgery in horses receiving flunixin meglumine or firocoxib. Transepithelial resistance of ischemic-injured jejunum from horses treated with flunixin meglumine was significantly lower than in saline- or firocoxib-treated horses. Lipopolysaccharide permeability across ischemic-injured mucosa was significantly increased in horses treated with flunixin meglumine. Treatment did not affect epithelial restitution. Cyclooxygenase-1 was constitutively expressed and COX-2 was upregulated after 2 hours of ischemia. Thromboxane B(2) concentration decreased with flunixin meglumine treatment but increased with firocoxib or saline treatment. Flunixin meglumine and firocoxib prevented an increase in PGEM concentration after surgery.

CONCLUSIONS AND CLINICAL RELEVANCE

Flunixin meglumine retarded mucosal recovery in ischemic-injured jejunum, whereas firocoxib did not. Flunixin meglumine and firocoxib were effective visceral analgesics. Firocoxib may be advantageous in horses recovering from ischemic intestinal injury.

Anti-inflammatory effects of intravenously administered lidocaine hydrochloride on ischemia-injured jejunum in horses

OBJECTIVE

To investigate effects of lidocaine hydrochloride administered IV on mucosal inflammation in ischemia-injured jejunum of horses treated with flunixin meglumine.

ANIMALS

24 horses.

PROCEDURES

Horses received saline (0.9% NaCl) solution (SS; 1 mL/50 kg, IV [1 dose]), flunixin meglumine (1 mg/kg, IV, q 12 h), lidocaine (bolus [1.3 mg/kg] and constant rate infusion [0.05 mg/kg/min], IV, during and after recovery from surgery), or both flunixin and lidocaine (n = 6/group). During surgery, blood flow was occluded for 2 hours in 2 sections of jejunum in each horse. Uninjured and ischemia-injured jejunal specimens were collected after the ischemic period and after euthanasia 18 hours later for histologic assessment and determination of cyclooxygenase (COX) expression (via western blot procedures). Plasma samples collected prior to (baseline) and 8 hours after the ischemic period were analyzed for prostanoid concentrations.

RESULTS

Immediately after the ischemic period, COX-2 expression in horses treated with lidocaine alone was significantly less than expression in horses treated with SS or flunixin alone. Eighteen hours after the ischemic period, mucosal neutrophil counts in horses treated with flunixin alone were significantly higher than counts in other treatment groups. Compared with baseline plasma concentrations, postischemia prostaglandin E(2) metabolite and thromboxane B(2) concentrations increased in horses treated with SS and in horses treated with SS or lidocaine alone, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

In horses with ischemia-injured jejunum, lidocaine administered IV reduced plasma prostaglandin E(2) metabolite concentration and mucosal COX-2 expression. Coadministration of lidocaine with flunixin ameliorated the flunixin-induced increase in mucosal neutrophil counts.

Effects of flunixin meglumine on recovery of colonic mucosa from ischemia in horses

OBJECTIVE

To examine the effects of flunixin meglumine (FM) on recovery of colonic mucosa from experimentally induced ischemia in horses.

ANIMALS

14 research horses.

PROCEDURES

Ischemia was induced in the colons of anesthetized horses for 2 hours. Afterward, horses received saline (0.9% NaCl) solution (12 mL, IV, q 12 h; n = 7) or FM (1.1 mg/kg, IV, q 12 h; 7) and were allowed to recover for 18 hours after termination of the ischemic event. Postoperative pain scores were recorded every 4 hours throughout the recovery period. At the end of the recovery period, horses were anesthetized, and ischemic and nonischemic segments of colonic mucosa were harvested for histologic evaluation, western blot analysis, and in vitro assessment of transepithelial electric resistance (TER) and transmucosal flux of tritium-labeled (3H-) mannitol. Horses were then euthanatized.

RESULTS

Flunixin meglumine significantly lowered pain scores at the first postoperative recording. There were no significant differences between treatment with saline solution and FM in any of the measurements for TER, 3H-mannitol flux, histomorphometric variables, neutrophil infiltration (detected via calprotectin immunostaining), and expressions of cyclooxygenase-1 and -2. After both treatments, TER declined significantly in nonischemic tissues in vitro, whereas it increased significantly in ischemic-injured tissues.

CONCLUSIONS AND CLINICAL RELEVANCE

Flunixin meglumine did not affect recovery of equine colonic mucosa from ischemic injury, and continued use in horses with colonic ischemia is therefore justified.