Pharmacokinetics of flunixin meglumine in mature swine after intravenous, intramuscular and oral administration

Validation of Standing and Locomotion Scoring, Behavioral Assessments, and Mechanical Nociceptive Threshold Testing on Naturally Occurring Sow Lameness

The objective of this study was to validate standing and locomotion lameness scoring, mechanical nociceptive threshold testing, and behavioral profile tools for the diagnosis of naturally occurring lameness etiologies in pigs. A total of 55 crossbred gilts and sows obtained from a commercial farm were enrolled in the study; with sound pigs classified as controls (8) and the remainder as lame due to integumentary (20), musculoskeletal (15), and combinations of integumentary and musculoskeletal (12) etiologies. Standing and locomotion lameness, mechanical nociceptive threshold (MNT) test, pig-human interventions, and latency to complete an obstacle course were evaluated. Standing and locomotion lameness scoring systems, MNT, and pig behavior (latency) were capable of discriminating between animals with mild organic lameness and animals that were sound and may have utility on the farm for staff to use to identify and manage lame animals. In rare instances, the tools used here were able to discriminate between broad categories of lameness etiology.

Lameness in Pregnant Sows Alters Placental Stress Response

Pregnant sows from commercial pig farms may experience painful states, such as lameness, an essential indicator in assessing sow welfare. We investigated the effect of lameness during the last third of pregnancy on reproductive performance and placental glucocorticoid concentrations in sows. Periodic locomotion assessments were carried out on two commercial pig farms using a validated 0-5 scoring system (from 0: normal locomotion; to 5: a downer animal). Sows from both farms (N = 511) were grouped based on their average locomotion scores. On Farm 1, 30 sows were selected and grouped as either Not Lame (NL = 16; X¯ = 0-1) or Lame (L = 14; X¯ > 1). On Farm 2, 39 sows were selected and grouped as either Not Lame (G1 = 12; X¯ = 0-1), Moderately Lame (G2 = 13; X¯ = 1.1-2), or Severely Lame (G3 = 14; X¯ ≥ 2.1). Reproductive data (gestation length, litter weight, average piglet weight, litter size, and the number of piglets born alive/mummified/stillborn) were recorded on both farms. Moreover, on Farm 2, piglet intrauterine growth restriction score and the number of piglets dead during the first week were also recorded, and placenta samples were collected to determine their cortisol/cortisone concentrations. A linear mixed model was used to analyze the data. The proportion of lameness in pregnant sows (N = 511) was >40%, and the gestation length tended to decrease with the presence of lameness (p < 0.1) in both farms. G2 sows had a higher placental cortisol/cortisone ratio than G1 and G3 sows (p < 0.01). In conclusion, lameness was high in the sows assessed, which may decrease sow gestation length and reduce placental efficiency in protecting the offspring from the sows' stress response.

Pharmacokinetics of combined administration of iron dextran with meloxicam or flunixin meglumine in piglets

OBJECTIVE

The objective was to evaluate the pharmacokinetics of compounding non-steroidal anti-inflammatory drugs (NSAIDs) meloxicam or flunixin meglumine with iron dextran (ID) in piglets.

ANIMAL

Forty piglets (8 d of age) were randomly allocated into 5 groups (8 piglets/group) and received 1 intramuscular injection in the neck of the following treatments: flunixin meglumine (2.2 mg/kg) administered alone (F) or mixed with ID (F+ID); or meloxicam (0.4 mg/kg) administered alone (M) or mixed with ID (M+ID); or ID alone.

PROCEDURE

Blood samples were collected via indwelling jugular catheters at pre-dose, and 10, 20, 30, 45, and 60 min, and 2, 4, 8, 12, 24, 36, 48, and 72 h post-treatment to determine plasma NSAIDs concentrations using liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters for plasma meloxicam and flunixin meglumine concentration-time profiles were determined for each piglet using noncompartmental analysis approaches. Statistical analyses were performed using SAS software with significance set at P < 0.05.

RESULTS

The AUC_0-tlast, AUC_0-∞, C_max, and relative bioavailability values in the M+ID and F+ID groups were lower than corresponding M and F groups. The M+ID group elimination half-life was lower, whereas λ_z and t_max values were greater than the corresponding M group.

CONCLUSION

Relative bioavailability of meloxicam and flunixin meglumine were reduced when compounded with ID in the same bottle and administered to piglets.

CLINICAL RELEVANCE

Further research is warranted to evaluate if decreased NSAID exposure when compounded with ID alters analgesic efficacy or drug residue depletion.

An Interactive Generic Physiologically Based Pharmacokinetic (igPBPK) Modeling Platform to Predict Drug Withdrawal Intervals in Cattle and Swine: A Case Study on Flunixin, Florfenicol and Penicillin G

Violative chemical residues in edible tissues from food-producing animals are of global public health concern. Great efforts have been made to develop physiologically based pharmacokinetic (PBPK) models for estimating withdrawal intervals (WDIs) for extralabel prescribed drugs in food animals. Existing models are insufficient to address the food safety concern as these models are either limited to 1 specific drug or difficult to be used by non-modelers. This study aimed to develop a user-friendly generic PBPK platform that can predict tissue residues and estimate WDIs for multiple drugs including flunixin, florfenicol, and penicillin G in cattle and swine. Mechanism-based in silico methods were used to predict tissue/plasma partition coefficients and the models were calibrated and evaluated with pharmacokinetic data from Food Animal Residue Avoidance Databank (FARAD). Results showed that model predictions were, in general, within a 2-fold factor of experimental data for all 3 drugs in both species. Following extralabel administration and respective U.S. FDA-approved tolerances, predicted WDIs for both cattle and swine were close to or slightly longer than FDA-approved label withdrawal times (eg, predicted 8, 28, and 7 days vs labeled 4, 28, and 4 days for flunixin, florfenicol, and penicillin G in cattle, respectively). The final model was converted to a web-based interactive generic PBPK platform. This PBPK platform serves as a user-friendly quantitative tool for real-time predictions of WDIs for flunixin, florfenicol, and penicillin G following FDA-approved label or extralabel use in both cattle and swine, and provides a basis for extrapolating to other drugs and species.

Plasma, urine and tissue concentrations of Flunixin and Meloxicam in Pigs

BACKGROUND

The objective of this study was to determine the renal clearance of flunixin and meloxicam in pigs and compare plasma and urine concentrations and tissue residues. Urine clearance is important for livestock show animals where urine is routinely tested for these drugs. Fourteen Yorkshire/Landrace cross pigs were housed in individual metabolism cages to facilitate urine collection. This is a unique feature of this study compared to other reports. Animals received either 2.2 mg/kg flunixin or 0.4 mg/kg meloxicam via intramuscular injection and samples analyzed by mass spectrometry. Pigs were euthanized when drugs were no longer detected in urine and liver and kidneys were collected to quantify residues.

RESULTS

Drug levels in urine reached peak concentrations between 4 and 8 h post-dose for both flunixin and meloxicam. Flunixin urine concentrations were higher than maximum levels in plasma. Urine concentrations for flunixin and meloxicam were last detected above the limit of quantification at 120 h and 48 h, respectively. The renal clearance of flunixin and meloxicam was 4.72 ± 2.98 mL/h/kg and 0.16 ± 0.04 mL/h/kg, respectively. Mean apparent elimination half-life in plasma was 5.00 ± 1.89 h and 3.22 ± 1.52 h for flunixin and meloxicam, respectively. Six of seven pigs had detectable liver concentrations of flunixin (range 0.0001-0.0012 µg/g) following negative urine samples at 96 and 168 h, however all samples at 168 h were below the FDA tolerance level (0.03 µg/g). Meloxicam was detected in a single liver sample (0.0054 µg/g) at 72 h but was below the EU MRL (0.065 µg/g).

CONCLUSIONS

These data suggest that pigs given a single intramuscular dose of meloxicam at 0.4 mg/kg or flunixin at 2.2 mg/kg are likely to have detectable levels of the parent drug in urine up to 2 days and 5 days, respectively, after the first dose, but unlikely to have tissue residues above the US FDA tolerance or EU MRL following negative urine testing. This information will assist veterinarians in the therapeutic use of these drugs prior to livestock shows and also inform livestock show authorities involved in testing for these substances.

Pharmacokinetics of Intravenous, Intramuscular, Oral, and Transdermal Administration of Flunixin Meglumine in Pre-wean Piglets

Castration and tail-docking of pre-wean piglets are common procedures that are known to induce pain and would benefit from pain mitigation. Flunixin meglumine (FM) is a non-steroidal anti-inflammatory drug currently approved in the United States for pyrexia in swine and lameness pain in cattle. The objective of this study was to establish the pharmacokinetic (PK) parameters resulting from intravenous (IV), intramuscular (IM), oral (PO) and transdermal (TD) administration of FM in pre-wean piglets. FM was administered to thirty-nine pre-wean piglets at a target dose of 2.2 mg/kg for IV and IM and 3.3 mg/kg for PO and TD route. Plasma was collected at twenty-seven time points from 0 to 9 days after FM administration and concentrations were determined using ultra-high performance liquid chromatography coupled with mass spectrometry (UPLC-MS). Pharmacokinetic data were analyzed using noncompartmental analysis (NCA) methods and nonlinear mixed-effects (NLME). Initial plasma concentration for IV (C₀) 11,653 μg/L and mean peak plasma concentrations (C_max) 6,543 μg/L (IM), 4,883 μg/L (PO), and 31.5 μg/L (TD) were measured. The time points of peak FM concentrations (t_max) were estimated 30 min, 1 h, and 24 h for IM, PO, and TD, respectively. The bioavailability (F) of PO and IM FM was estimated at >99%, while the bioavailability of TD FM was estimated to be 7.8%. The reported C_max of FM after IM and PO administration is consistent with therapeutic concentration ranges that mitigate pain in other species and adult pigs. However, the low estimated concentration of FM after TD dosing is not expected to mitigate pain in pre-wean piglets. The low F of TD FM suggests that expanding the surface area of application is unlikely to be sufficient to establish an effective TD dose for pain, while the high bioavailability for PO FM should allow for an effective dose regimen to be established.

A study to assess the correlation between plasma, oral fluid and urine concentrations of flunixin meglumine with the tissue residue depletion profile in finishing-age swine

Background

Flunixin meglumine (FM) was investigated for the effectiveness of plasma, oral fluid, and urine concentrations to predict tissue residue depletion profiles in finishing-age swine, along with the potential for untreated pigs to acquire tissue residues following commingled housing with FM-treated pigs. Twenty pigs were housed in groups of three treated and one untreated control. Treated pigs received one 2.2 mg/kg dose of FM intramuscularly. Before treatment and at 1, 3, 6, 12, 24, 36, and 48 h (h) after treatment, plasma samples were taken. At 1, 4, 8, 12 and 16 days (d) post-treatment, necropsy and collection of plasma, urine, oral fluid, muscle, liver, kidney, and injection site samples took place. Analysis of flunixin concentrations using liquid chromatography/tandem mass spectrometry was done. A published physiologically based pharmacokinetic (PBPK) model for flunixin in cattle was extrapolated to swine to simulate the measured data.

Results

Plasma concentrations of flunixin were the highest at 1 h post-treatment, ranging from 1534 to 7040 ng/mL, and were less than limit of quantification (LOQ) of 5 ng/mL in all samples on Day 4. Flunixin was detected in the liver and kidney only on Day 1, but was not found 4–16 d post-treatment. Flunixin was either not seen or found less than LOQ in the muscle, with the exception of one sample on Day 16 at a level close to LOQ. Flunixin was found in the urine of untreated pigs after commingled housing with FM-treated pigs. The PBPK model adequately correlated plasma, oral fluid and urine concentrations of flunixin with residue depletion profiles in liver, kidney, and muscle of finishing-age pigs, especially within 24 h after dosing.

Conclusions

Results indicate untreated pigs can be exposed to flunixin by shared housing with FM-treated pigs due to environmental contamination. Plasma and urine samples may serve as less invasive and more easily accessible biological matrices to predict tissue residue statuses of flunixin in pigs at earlier time points (≤24 h) by using a PBPK model.

Lateral flow immunoassay for 5-hydroxyflunixin based on near-infrared fluorescence molecule as an alternative label to gold nanoparticles

A high-affinity monoclonal antibody (mAb) has been prepared and separately a gold nanoparticle (AuNP)-based and a near-infrared (NIR) fluorescence-based lateral flow immunoassay (LFA) developed for determination of 5-hydroxyflunixin residue in raw milk. The AuNP and IRDye® 800CW were used to label anti-5-hydroxyflunixin mAb to form the AuNP-mAb and NIR dye-mAb conjugates, respectively. Quantitative determination of 5-hydroxyflunixin was achieved by imaging the optical or fluorescence intensity of the AuNP-mAb and NIR dye-mAb captured on the test line. As a result, the detection limits of the AuNP-based LFA and NIR dye-based LFA were 0.82 and 0.073 ng/mL in raw milk, respectively. The considerable improvement on assay sensitivity of the NIR-based LFA can be attributed to the lower background and less antibody consumption per test than that of the AuNP-based LFA. The spiking experiment by the NIR-based LFA yielded 85.7-112.6% recovery with a relative standard deviation below 14%, indicating that it has satisfactory assay accuracy and precision. Furthermore, the analytical results of actual samples by the NIR dye-based LFA were consistent with that by instrumental analysis. Therefore, these results demonstrated that the NIR dye is an ideal alternative label to the conventional AuNP for the development of LFA for veterinary drugs in animal-origin food. Graphical abstract.

Validation of the UNESP-Botucatu pig composite acute pain scale (UPAPS)

The creation of species-specific valid tools for pain assessment is essential to recognize pain and determine the requirement and efficacy of analgesic treatments. This study aimed to assess behaviour and investigate the validity and reliability of an acute pain scale in pigs undergoing orchiectomy. Forty-five pigs aged 38±3 days were castrated under local anaesthesia. Behaviour was video-recorded 30 minutes before and intermittently up to 24 hours after castration. Edited footage (before surgery, after surgery before and after rescue analgesia, and 24 hours postoperatively) was analysed twice (one month apart) by one observer who was present during video-recording (in-person researcher) and three blinded observers. Statistical analysis was performed using R software and differences were considered significant when p<0.05. Intra and inter-observer agreement, based on intra-class correlation coefficient, was good or very good between most observers (>0.60), except between observers 1 and 3 (moderate agreement 0.57). The scale was unidimensional according to principal component analysis. The scale showed acceptable item-total Spearman correlation, excellent predictive and concurrent criterion validity (Spearman correlation ≥ 0.85 between the proposed scale versus visual analogue, numerical rating, and simple descriptive scales), internal consistency (Cronbach's α coefficient >0.80 for all items), responsiveness (the pain scores of all items of the scale increased after castration and decreased after intervention analgesia according to Friedman test), and specificity (> 95%). Sensitivity was good or excellent for most of the items. The optimal cut-off point for rescue analgesia was ≥ 6 of 18. Discriminatory ability was excellent for all observers according to the area under the curve (>0.95). The proposed scale is a reliable and valid instrument and may be used clinically and experimentally to assess postoperative acute pain in pigs. The well-defined cut-off point supports the evaluator´s decision to provide or not analgesia.

Comparative Plasma and Interstitial Fluid Pharmacokinetics of Meloxicam, Flunixin, and Ketoprofen in Neonatal Piglets

Piglet castration and tail-docking are routinely performed in the United States without analgesia. Pain medications, predominately non-steroidal anti-inflammatory drugs, are used in the EU/Canada to decrease pain associated with processing and improve piglet welfare, however, past studies have shown the efficacy and required dose remain controversial, particularly for meloxicam. This study assessed the pharmacokinetics of three NSAIDs (meloxicam, flunixin, and ketoprofen) in piglets prior to undergoing routine castration and tail-docking. Five-day-old male piglets (8/group) received one of 3 randomized treatments; meloxicam (0.4 mg/kg), flunixin (2.2 mg/kg), ketoprofen (3.0 mg/kg). Two hours post-dose, piglets underwent processing. Drug concentrations were quantified in plasma and interstitial fluid (ISF) and pharmacokinetic parameters were generated by non-compartmental analysis. Time to peak concentration (T_max) of meloxicam, flunixin, and S(-)-ketoprofen in plasma were 1.21, 0.85, and 0.59 h, compared to 2.81, 3.64, and 2.98 h in the ISF, respectively. The apparent terminal half-life of meloxicam, flunixin and S(-)-ketoprofen were 4.39, 7.69, and 3.50 h, compared to 11.26, 16.34, and 5.54 h, respectively in the ISF. If drug concentrations in the ISF are more closely related to efficacy than the plasma, then the delay between the Tmax in plasma and ISF may be relevant to the timing of castration in order to provide the greatest analgesic effect.

Transmammary delivery of firocoxib to piglets reduces stress and improves average daily gain after castration, tail docking, and teeth clipping1

Painful processing procedures in piglets such as tail docking, castration, and teeth clipping are an emerging animal welfare concern. We hypothesized that transmammary delivery of a nonsteroidal anti-inflammatory drug, firocoxib, would reduce pain associated with processing in piglets. This study compared the pharmacokinetics, efficacy, safety, and tissue residue concentrations of 4 doses of firocoxib (0.5, 1.0, 1.5, or 2.0 mg/kg) administered to sows and delivered to nursing piglets prior to processing. Sixteen sows, 5 ± 2 d postpartum, were randomly assigned to 1 of 4 treatment groups. On day 0, sows received a single intramuscular dose of firocoxib at 7 ± 1 h before piglet surgical castration, tail docking, and teeth clipping (males) or sham handling (females). Firocoxib and cortisol concentrations were determined from selected samples collected from sows and 3 piglets per litter (2 barrows and 1 gilt) at 0, 2, 4, 6, 8, 12, 24, 48, 72, 96, and 120 h after drug administration. On day 21, piglets were weighed and all animals were euthanized and necropsied. Tissues were collected from 3 piglets per litter for histological examination and drug residue analysis. Mean (±SEM) peak plasma firocoxib concentrations (Cmax) were 107.90 ± 15.18, 157.50 ± 24.91, 343.68 ± 78.89, and 452.83 ± 90.27 ng/mL in sows receiving 0.5, 1.0, 1.5, and 2.0 mg/kg firocoxib, respectively, and 9.53 ± 1.21, 31.04 ± 6.79, 53.30 ± 11.1, and 44.03 ± 7.47 ng/mL in their respective piglets. Mean plasma terminal half-life values ranged from 26 to 31 h in sows and 30 to 48 h in piglets. Barrows nursing sows that received 2.0 mg/kg firocoxib had a lower mean plasma cortisol concentration at 1 ± 1 h after processing compared with barrows nursing sows that received 1.0 mg/kg (P = 0.0416) and 0.5 mg/kg of firocoxib (P = 0.0397). From processing to weaning, litters of sows receiving 2.0 mg/kg firocoxib gained more weight than litters of sows that received 0.5 mg/kg (P = 0.008) or 1.0 mg/kg (P = 0.005). No signs of nonsteroidal anti-inflammatory drug toxicity were observed on examination of the kidney, liver, stomach, and small intestine, and concentrations of firocoxib and the descyclopropylmethyl metabolite were below the limit of detection (0.01 µg/g) in all tissues examined from sows and piglets. These findings indicate that maternal delivery of firocoxib to suckling piglets before tail docking and castration may safely reduce processing-induced stress and enhance production by increasing weaning weights.

Pharmacokinetics of transdermal flunixin in sows

The objective of this study was to describe the pharmacokinetics (PK) of flunixin in 12 nonlactating sows following transdermal (TD) flunixin (3.33 mg/kg) and intravenous (IV; 2.20 mg/kg) flunixin meglumine (FM) administration using a crossover design with a 10-day washout period. Blood samples were collected postadministration from sows receiving IV FM (3, 6, 10, 20, 40 min and 1, 3, 6, 12, 16, 24, 36, and 48 hr) and from sows receiving TD flunixin (10, 20, 40 min and 1, 2, 3, 4, 6, 8, 12, 16, 24, 36, 48, 60, and 72 hr). Liquid chromatography and mass spectrometry were used to determine plasma flunixin concentrations, and noncompartmental methods were used for PK analysis. The geometric mean ± SD area under the plasma concentration-time curve (AUC) following IV injection was 26,820.59 ± 9,033.88 and 511.83 ± 213.98 hr ng/ml for TD route. Mean initial plasma concentration (C₀ ) was 26,279.70 ± 3,610.00 ng/ml, and peak concentration (C_max ) was 14.61 ± 7.85 ng/ml for IV and TD administration, respectively. The percent mean bioavailability of TD flunixin was 1.55 ± 1.00. Our results demonstrate that topical administration is not an efficient route for delivering flunixin in mature sows.

Use of non-steroidal anti-inflammatory drugs in porcine health management

OBJECTIVE

Treatment of inflammation and pain management is an important topic in the welfare of pigs. It is very difficult for veterinary practitioners to choose the most appropriate product for a certain problem. This review aims to summarise and discuss the characteristics of different non-steroidal anti-inflammatory drugs (NSAIDs), as well as paracetamol and metamizole, available for pigs in the European Union.

METHODS

The databases Pubmed, Google Scholar, CliniPharm CliniTox and European Medicines Agency were searched. Relevant terms (eg,'meloxicam', 'fever', 'swine', 'pig', 'inflammation', 'castration', 'pain') were used to search for original articles, reviews and books. Only peer-reviewed articles were used. References from studies were also analysed in order to find additional relevant studies.

CONCLUSION

Studies which have investigated the efficacy of NSAIDs for different conditions, using different treatment regimens, are scarce. Most studies focused on the efficacy of NSAID-related pain alleviation in piglet castration, as well as the anti-inflammatory potential of NSAIDs in experimental inflammation models. Little research has been carried out on the use of metamizole, tolfenamic acid, paracetamol and sodium salicylate and their effect in pigs.

Integration of Food Animal Residue Avoidance Databank (FARAD) empirical methods for drug withdrawal interval determination with a mechanistic population-based interactive physiologically based pharmacokinetic (iPBPK) modeling platform: example for flunixin meglumine administration

Violative chemical residues in animal-derived food products affect food safety globally and have impact on the trade of international agricultural products. The Food Animal Residue Avoidance Databank program has been developing scientific tools to provide appropriate withdrawal interval (WDI) estimations after extralabel drug use in food animals for the past three decades. One of the tools is physiologically based pharmacokinetic (PBPK) modeling, which is a mechanistic-based approach that can be used to predict tissue residues and WDIs. However, PBPK models are complicated and difficult to use by non-modelers. Therefore, a user-friendly PBPK modeling framework is needed to move this field forward. Flunixin was one of the top five violative drug residues identified in the United States from 2010 to 2016. The objective of this study was to establish a web-based user-friendly framework for the development of new PBPK models for drugs administered to food animals. Specifically, a new PBPK model for both cattle and swine after administration of flunixin meglumine was developed. Population analysis using Monte Carlo simulations was incorporated into the model to predict WDIs following extralabel administration of flunixin meglumine. The population PBPK model was converted to a web-based interactive PBPK (iPBPK) framework to facilitate its application. This iPBPK framework serves as a proof-of-concept for further improvements in the future and it can be applied to develop new models for other drugs in other food animal species, thereby facilitating the application of PBPK modeling in WDI estimation and food safety assessment.

Plasma pharmacokinetic profile and efficacy of meloxicam administered subcutaneously and intramuscularly to sheep

Plasma pharmacokinetic profiles and the anti-inflammatory efficacy of meloxicam were determined when administered subcutaneously (SC) or intramuscularly (IM) to sheep. Merino ewes were initially injected with 0.1 mL of oil of turpentine into a forelimb to induce inflammation, followed by either 1.0 mg/kg or 2.0 mg/kg of meloxicam administered either SC or IM (n = 6 per treatment group) or followed by no meloxicam administration (control) (n = 4). Ewes were examined to determine skin temperature, limb circumference, limb sensitivity and signs of lameness at 0, 0.5, 1, 2, 4, 6, 8, 10, 12, 24 and 48 h following treatment, with blood collected at these time-points to quantify meloxicam plasma concentrations. Skin temperature of ewes dosed with meloxicam at 1.0 mg/kg SC and 2.0 mg/kg IM at 12 h and 1.0 mg/kg SC at 24 were significantly different to the controls (P < 0.05). Limb circumferences of ewes dosed with 1.0 mg/kg IM were significantly different to controls at 10 h and 12 h (P < 0.05). All meloxicam treatment groups resulted in reduced limb sensitivity compared to controls at 6 h, with the 1.0 and 2.0 mg/kg IM treatments significantly different at 12 h (P < 0.05) and 1.0 and 2.0 mg/kg SC groups, significantly different to controls at 48 h (P < 0.05). No significant difference in lameness scores were detected over 48 h. The 1.0 mg/kg IM treatment had a significantly greater plasma meloxicam concentration than the 1.0 mg/kg SC treatment over 0.5 to 4 h (P < 0.001). Both 1.0 mg/kg SC and IM treatments demonstrated elimination half-lives (mean ± SD) of 10.82 ± 2.46 and 12.63 ± 2.37 h, respectively. Meloxicam at all doses provided some anti-inflammatory and analgesic effects from 6 to 48 h; however no route could be distinguished as more efficacious than the others.

Genetic Parameter Estimates for Metabolizing Two Common Pharmaceuticals in Swine

In livestock, the regulation of drugs used to treat livestock has received increased attention and it is currently unknown how much of the phenotypic variation in drug metabolism is due to the genetics of an animal. Therefore, the objective of the study was to determine the amount of phenotypic variation in fenbendazole and flunixin meglumine drug metabolism due to genetics. The population consisted of crossbred female and castrated male nursery pigs (n = 198) that were sired by boars represented by four breeds. The animals were spread across nine batches. Drugs were administered intravenously and blood collected a minimum of 10 times over a 48 h period. Genetic parameters for the parent drug and metabolite concentration within each drug were estimated based on pharmacokinetics (PK) parameters or concentrations across time utilizing a random regression model. The PK parameters were estimated using a non-compartmental analysis. The PK model included fixed effects of sex and breed of sire along with random sire and batch effects. The random regression model utilized Legendre polynomials and included a fixed population concentration curve, sex, and breed of sire effects along with a random sire deviation from the population curve and batch effect. The sire effect included the intercept for all models except for the fenbendazole metabolite (i.e., intercept and slope). The mean heritability across PK parameters for the fenbendazole and flunixin meglumine parent drug (metabolite) was 0.15 (0.18) and 0.31 (0.40), respectively. For the parent drug (metabolite), the mean heritability across time was 0.27 (0.60) and 0.14 (0.44) for fenbendazole and flunixin meglumine, respectively. The errors surrounding the heritability estimates for the random regression model were smaller compared to estimates obtained from PK parameters. Across both the PK and plasma drug concentration across model, a moderate heritability was estimated. The model that utilized the plasma drug concentration across time resulted in estimates with a smaller standard error compared to models that utilized PK parameters. The current study found a low to moderate proportion of the phenotypic variation in metabolizing fenbendazole and flunixin meglumine that was explained by genetics in the current study.

PK/PD modeling of flunixin meglumine in a kaolin-induced inflammation model in piglets

Flunixin is marketed in several countries for analgesia in adult swine but little is known about its efficacy in piglets. Thirty-two piglets (6-8 days old) were randomized to receive placebo saline (n = 11, group CONTROL) or flunixin meglumine intravenously at 2.2 (n = 11, group MEDIUM) or 4.4 (n = 10, group HIGH) mg/kg, 10 hr after subcutaneous injection of kaolin in the left metacarpal area. A hand-held algometer was used to determine each piglet's mechanical nociceptive threshold (MNT) from both front feet up to 50 hr after treatment (cut-off value of 24.5 newton). Serial venous blood samples were obtained to quantify flunixin in plasma using LC-MS/MS. A PKPD model describing the effect of flunixin on the mechanical nociceptive threshold was obtained based on an inhibitory indirect response model. A two-compartmental PK model was used. A significant effect of flunixin was observed for both doses compared to control group, with 4.4 mg/kg showing the most relevant (6-10 newton) and long-lasting effect (34 hr). The median IC50 was 6.78 and 2.63 mg/ml in groups MEDIUM and HIGH, respectively. The ED50 in this model was 6.6 mg/kg. Flunixin exhibited marked antinociceptive effect on kaolin-induced inflammatory hyperalgesia in piglets.

Gene co-expression network analysis identifies porcine genes associated with variation in metabolizing fenbendazole and flunixin meglumine in the liver

Identifying individual genetic variation in drug metabolism pathways is of importance not only in livestock, but also in humans in order to provide the ultimate goal of giving the right drug at the right dose at the right time. Our objective was to identify individual genes and gene networks involved in metabolizing fenbendazole (FBZ) and flunixin meglumine (FLU) in swine liver. The population consisted of female and castrated male pigs that were sired by boars represented by 4 breeds. Progeny were randomly placed into groups: no drug (UNT), FLU or FBZ administered. Liver transcriptome profiles from 60 animals with extreme (i.e. fast or slow drug metabolism) pharmacokinetic (PK) profiles were generated from RNA sequencing. Multiple cytochrome P450 (CYP1A1, CYP2A19 and CYP2C36) genes displayed different transcript levels across treated versus UNT. Weighted gene co-expression network analysis identified 5 and 3 modules of genes correlated with PK parameters and a portion of these were enriched for biological processes relevant to drug metabolism for FBZ and FLU, respectively. Genes within identified modules were shown to have a higher transcript level relationship (i.e. connectivity) in treated versus UNT animals. Investigation into the identified genes would allow for greater insight into FBZ and FLU metabolism.

Effect of propofol and remifentanil on cerebral perfusion and oxygenation in pigs: a systematic review

The objective of this review is to evaluate the existing literature with regard to the influence of propofol and remifentanil total intravenous anaesthesia (TIVA) on cerebral perfusion and oxygenation in healthy pigs. Anaesthesia has influence on cerebral haemodynamics and it is important not only in human but also in veterinary anaesthesia to preserve optimal regulation of cerebral haemodynamics. Propofol and remifentanil are widely used in neuroanaesthesia and are increasingly used in experimental animal studies. In translational models, the pig has advantages compared to small laboratory animals because of brain anatomy, metabolism, neurophysiological maturation, and cerebral haemodynamics. However, reported effects of propofol and remifentanil on cerebral perfusion and oxygenation in pigs have not been reviewed. An electronic search identified 99 articles in English. Title and abstract screening selected 29 articles for full-text evaluation of which 19 were excluded with reasons. Of the 10 peer-reviewed articles included for review, only three had propofol or remifentanil anaesthesia as the primary study objective and only two directly investigated the effect of anaesthesia on cerebral perfusion and oxygenation (CPO). The evidence evaluated in this systematic review is limited, not focused on propofol and remifentanil and possibly influenced by factors of potential importance for CPO assessment. In one study of healthy pigs, CPO measures were within normal ranges following propofol-remifentanil anaesthesia, and addition of a single remifentanil bolus did not affect regional cerebral oxygen saturation (rSO2). Even though the pool of evidence suggests that propofol and remifentanil alone or in combination have limited effects on CPO in healthy pigs, confirmative evidence is lacking.

Measuring the efficacy of flunixin meglumine and meloxicam for lame sows using a GAITFour pressure mat and an embedded microcomputer-based force plate system

Pain associated with lameness on farm is a negative affective state and has a detrimental impact on individual farm animal welfare. Animal pain can be managed utilizing husbandry tools and through pharmacological approaches. Nonsteroidal anti-inflammatory drugs including meloxicam and flunixin meglumine are compounds used in many species for pain management because they are easy to administer, long lasting, and cost-effective. Assessing an animal's biomechanical parameters using such tools as the embedded microcomputer-based force plate system and GAITFour pressure mat gait analysis walkway system provides an objective, sensitive, and precise means to detect animals in lame states. The objectives of this study were to determine the efficacy of meloxicam and flunixin meglumine for pain mitigation in lame sows using the embedded microcomputer-based force plate system and GAITFour pressure mat gait analysis walkway system. Lameness was induced in 24 mature mixed-parity sows using a chemical synovitis model and compared 3 treatments: meloxicam (1.0 mg/kg per os), flunixin meglumine (2.2 mg/kg intramuscular) and sterile saline (intramuscular). Weight distribution (kg) for each foot was collected twice per second for a total of 5 min for each time point using the embedded microcomputer-based force plate system. Stride time, stride length, maximum pressure, activated sensors, and stance time were collected using 3 quality walks (readings) for each time point using the GAITFour pressure mat gait analysis walkway system. Sows administered flunixin meglumine or meloxicam tolerated more weight on their lame leg compared with saline sows (P < 0.005). Sows administered flunixin meglumine or meloxicam had smaller differences in stance time, maximum pressure, and activated sensors between the sound and lame legs compared with saline-treated sows between 37 and 60 h after lameness induction (P < 0.03). In conclusion, flunixin meglumine and meloxicam administration mitigated pain sensitivity in sows after lameness induction when pain sensitivity was evaluated with the embedded microcomputer-based force plate system and GAITFour pressure mat gait analysis walkway system. Analgesic drugs may be a key tool to manage negative pain affective states associated with lameness.

Differential Gene Expression across Breed and Sex in Commercial Pigs Administered Fenbendazole and Flunixin Meglumine

Characterizing the variability in transcript levels across breeds and sex in swine for genes that play a role in drug metabolism may shed light on breed and sex differences in drug metabolism. The objective of the study is to determine if there is heterogeneity between swine breeds and sex in transcript levels for genes previously shown to play a role in drug metabolism for animals administered flunixin meglumine or fenbendazole. Crossbred nursery female and castrated male pigs (n = 169) spread across 5 groups were utilized. Sires (n = 15) of the pigs were purebred Duroc, Landrace, Yorkshire or Hampshire boars mated to a common sow population. Animals were randomly placed into the following treatments: no drug (control), flunixin meglumine, or fenbendazole. One hour after the second dosing, animals were sacrificed and liver samples collected. Quantitative Real-Time PCR was used to measure liver gene expression of the following genes: SULT1A1, ABCB1, CYP1A2, CYP2E1, CYP3A22 and CYP3A29. The control animals were used to investigate baseline transcript level differences across breed and sex. Post drug administration transcript differences across breed and sex were investigated by comparing animals administered the drug to the controls. Contrasts to determine fold change were constructed from a model that included fixed and random effects within each drug. Significant (P-value <0.007) basal transcript differences were found across breeds for SULT1A1, CYP3A29 and CYP3A22. Across drugs, significant (P-value <0.0038) transcript differences existed between animals given a drug and controls across breeds and sex for ABCB1, PS and CYP1A2. Significant (P <0.0038) transcript differences across breeds were found for CYP2E1 and SULT1A1 for flunixin meglumine and fenbendazole, respectively. The current analysis found transcript level differences across swine breeds and sex for multiple genes, which provides greater insight into the relationship between flunixin meglumine and fenbendazole and known drug metabolizing genes.

The effect of breed and sex on sulfamethazine, enrofloxacin, fenbendazole and flunixin meglumine pharmacokinetic parameters in swine

Drug use in livestock has received increased attention due to welfare concerns and food safety. Characterizing heterogeneity in the way swine populations respond to drugs could allow for group-specific dose or drug recommendations. Our objective was to determine whether drug clearance differs across genetic backgrounds and sex for sulfamethazine, enrofloxacin, fenbendazole and flunixin meglumine. Two sires from each of four breeds were mated to a common sow population. The nursery pigs generated (n = 114) were utilized in a random crossover design. Drugs were administered intravenously and blood collected a minimum of 10 times over 48 h. A non-compartmental analysis of drug and metabolite plasma concentration vs. time profiles was performed. Within-drug and metabolite analysis of pharmacokinetic parameters included fixed effects of drug administration date, sex and breed of sire. Breed differences existed for flunixin meglumine (P-value<0.05; Cl, Vdss ) and oxfendazole (P-value<0.05, AUC0→∞ ). Sex differences existed for oxfendazole (P-value < 0.05; Tmax ) and sulfamethazine (P-value < 0.05, Cl). Differences in drug clearance were seen, and future work will determine the degree of additive genetic variation utilizing a larger population.