Evaluation of flunixin meglumine pour-on administration on prostaglandin E2 concentration in inflammatory exudate after induction of inflammation in cattle

Effects of a single transdermal administration of flunixin meglumine in early postpartum Holstein Friesian dairy cows: Part 1. Inflammatory and metabolic markers, uterine health, and indicators of pain

The objectives of this study were to assess the effects of a single transdermal administration of flunixin meglumine (FM) in early postpartum Holstein Friesian dairy cows on serum concentrations of inflammatory and metabolic markers, uterine health, and indicators of pain. The hypothesis was that the anti-inflammatory, antipyretic, and analgetic effects of the pharmaceutic agent would reduce systemic inflammation, resulting in improved metabolic and inflammatory profile, diminished incidence of metritis, and reduced expression of pain. A total of 500 cows (153 primiparous, 347 multiparous) from 3 different commercial dairy farms in the northeast of Germany were included in a randomized controlled clinical trial. Farms were preselected based on high haptoglobin concentrations in their fresh lactating cows. Cows were excluded if they had experienced dystocia, stillbirth, or twin birth, or if they showed any signs of milk fever, retained fetal membranes, or fever (>40°C). The cows were treated once with either FM (3.33 mg/kg) or a placebo as control (CON) through transdermal administration between 24 to 36 h postpartum (d 2). General health examinations were performed (daily from d 2-8 and additionally on d 15 postpartum), vaginal discharge was assessed using the Metricheck device (d 8 and 15 postpartum) and serum samples were analyzed for inflammatory and metabolic markers (d 2, 4, and 6 postpartum). Effects of treatment, parity, sampling day, and their interactions were evaluated using mixed effects models. Primiparous cows treated with FM showed lower serum haptoglobin concentrations (0.90 ± 0.08 vs. 1.17 ± 0.07 g/L; ± standard error of the mean) and higher serum albumin concentrations (35.5 ± 0.31 vs. 34.8 ± 0.31 g/L) on d 6 postpartum. They also had a lower risk for purulent vaginal discharge with or without a fever compared with CON cows on d 15 postpartum (odds ratio for CON vs. FM: 1.63, 95% CI: 1.26-2.00), and body temperature was lower throughout the first 15 d in milk (39.1 ± 0.11 vs. 39.2 ± 0.11°C). Multiparous cows treated with FM had lower serum β-hydroxybutyrate concentrations on d 4 postpartum (0.71 ± 0.05 vs. 0.78 ± 0.05 mmol/L) and d 6 postpartum (0.74 ± 0.05 vs. 0.80 ± 0.05 mmol/L). Regardless of parity, FM-treated cows were significantly less likely to abduct their tail from their body (14.3 vs. 23.6%) and show an arched back (27.9 vs. 39.7%) on the day after treatment compared with CON cows. It can be concluded that FM treatment slightly reduced inflammation and diminished the risk for metritis in primiparous cows, improved metabolic profile in multiparous cows, and reduced expressions of pain in all cows.

The pharmacokinetics of transdermal flunixin in lactating dairy goats

Flunixin is a nonsteroidal anti-inflammatory drug approved for use in cattle to manage pyrexia associated with bovine respiratory disease, mastitis, and endotoxemia. In the United States, no nonsteroidal anti-inflammatory drugs are approved for use in goats, but analgesics are needed for management of painful conditions to improve animal welfare. The objective of this study was to evaluate the pharmacokinetics of transdermal flunixin in dairy goats to determine a milk withdrawal interval (WDI) to avoid violative residue contamination in the food supply. Six adult lactating dairy goats received 3.3 mg/kg of transdermal flunixin before milk, interstitial fluid (ISF), and blood samples were collected at various time points for 360 h. The samples were analyzed using tandem mass spectrometry to detect flunixin as well as the flunixin marker metabolite, 5-hydroxyflunixin followed by a pharmacokinetic WDI calculation using the US Food and Drug Administration tolerance limit method to propose safe residue levels in goat milk. The mean flunixin apparent plasma half-life was 21.63 h. The apparent milk half-life for 5-hydroxyflunixin was 17.52 h. Our findings provide a milk WDI of 60 h using the US Food and Drug Administration tolerance of 0.002 µg/mL (established for bovine milk) and a more conservative WDI of 96 h using a limit of quantification of 0.001 µg/mL following the extralabel use of transdermal flunixin in dairy goats.

Evaluation of the pharmacokinetics and efficacy of transdermal flunixin for pain mitigation following castration in goats

The mitigation of pain associated with common management procedures is a rising concern among veterinarians, producers and consumers. Nonsteroidal anti-inflammatory drugs are vital compounds for this purpose due to their cost, convenience, and efficacy. A transdermal formulation of flunixin meglumine (FM) was approved for the treatment of pain in cattle; however, the efficacy has yet to be determined for small ruminants. The current study had two aims: 1) to determine the pharmacokinetics of transdermal flunixin meglumine (TD FM) in bucklings and 2) to evaluate pain mitigation by TD FM following castration. To evaluate pharmacokinetics, 12 male goats (mean age = 6 mo) received 2.2 mg/kg of FM IV (n = 6) or 3.3 mg/kg TD FM (n = 6). Plasma FM concentrations were measured. The mean C_max, T_max, and harmonic mean half-life for TD FM were 1.09 ± 0.65 μg/mL, 5.50 ± 2.95 h, and 7.16 ± 2.06 h, respectively. To evaluate the efficacy of pain mitigation, 18 goats were randomly assigned to three treatment groups: 1) TD FM and castration (FM CAST) (n = 6); 2) transdermal placebo and castration (PL CAST) (n = 6); and 3) TD FM and sham castration (SHAM) (n = 6). Plasma samples were collected at 0, 12, 24, 36, 48, 72, and 96 h to assess cortisol and prostaglandin E₂ (PGE₂)_. Daily dry matter intake (DMI) was recorded and body weight was measured at the beginning and end of the study. Thermography (IRT) images of the scrotum, as well as heart rate (HR), respiratory rate (RR), and rectal temperature, were taken twice daily. Separate mixed analysis of variance models were used to test the effects of treatment, time, and their interaction on mean body temperature, IRT, HR, and RR. Autoregressive covariance structure was utilized to account for repeated measures and individual goat DMI prior to the study was added as a covariate. There were no differences in vital parameters, IRT measurements, cortisol, or PGE₂ in animals receiving either TD FM or placebo following castration (P > 0.05). DMI had a treatment by hour interaction and was significantly higher in FM CAST and SHAM groups than the PL CAST group (P = 0.04). Goats in the SHAM group gained weight throughout the study, whereas goats in all other groups lost weight (P = 0.02). Results indicate that TD FM may mitigate pain as demonstrated by increased DMI; however, a single dose may not be sufficient to reduce physiological indicators of pain associated with castration in goats.

Pharmacokinetics of Transdermal Flunixin Meglumine Following a Single Dose in Marine Toads (Rhinella marina)

Transdermal administration is an important method of pharmacologic drug therapy in amphibians, made possible by their unique skin physiology and permeability. Despite this, there are relatively few studies that investigate transdermal pharmacokinetics in amphibians. The objective of this study was to investigate the pharmacokinetics of transdermal flunixin meglumine applied topically to marine toads (Rhinella marina). Twenty-one adult marine toads were administered flunixin meglumine (3.3 mg/kg) topically on their dorsum and randomized (n = 7/group) to blood collection at two timepoints from the following: 1, 2, 4, 8, 12, and 24 hours (h), using a sparse sampling protocol. Plasma was analyzed by ultra-performance liquid chromatography-tandem mass spectrometry. Samples were analyzed individually and reported as a mean of the samples at each timepoint. The mean peak plasma concentration was 6.31 µg/ml, area under the curve was 29.37 μg-h/mL, and elimination half-life was 2.79 h. No adverse effects were noted in any animals. A subset of 12 animals were euthanized at serial timepoints and necropsied. Histopathology of skin and major organs revealed one minimal superficial lesion in a single toad potentially attributable to flunixin meglumine administration; otherwise, no other treatment-related lesions were observed in 11 of 12 toads. A single topical dose of transdermal flunixin meglumine was rapidly absorbed in marine toads in the current study, and peak plasma concentrations exceeded therapeutic ranges established in cattle with no significant pathologic findings.

The effects of baicalin on piglets challenged with Glaesserella parasuis

Glaesserella parasuis (G. parasuis) causes porcine vascular inflammation and damage. Baicalin is reported to have antioxidant and anti-inflammatory functions. However, whether baicalin protects piglets against G. parasuis challenge and the potential protective mechanism have not been investigated. Therefore, in this study, we comprehensively examined the protective efficacy of baicalin in piglets challenged with G. parasuis and the possible protective mechanism. Our results show that baicalin attenuated the release of the inflammation-related cytokines interleukin (IL) 1β, IL6, IL8, IL10, and tumour necrosis factor α (TNF-α) and reduced high mobility group box 1 (HMGB1) production and cell apoptosis in piglets infected with G. parasuis. Baicalin also inhibited the activation of the mitogen-activated protein kinase (MAPK) signalling pathway and protected piglets against G. parasuis challenge. Taken together, our data suggest that baicalin could protect piglets from G. parasuis by reducing HMGB1 release, attenuating cell apoptosis, and inhibiting MAPK signalling activation, thereby alleviating the inflammatory response induced by the bacteria. Our results suggest that baicalin has utility as a novel therapeutic drug to control G. parasuis infection.

Comparison of the effect of tildipirosin administered alone or in combination with transdermal flunixin on the performance, health, activity, and well-being of transported feedlot calves on arrival at the feedlot

Long distance transportation can be a significant source of stress to cattle and is associated with increased risk of bovine respiratory disease (BRD). The administration of a nonsteroidal anti-inflammatory drug (NSAID) has been shown to reduce stress following long distance transport. The objective of this study was to compare performance, health, accelerometer activity, and well-being between calves receiving either tildipirosin (Zuprevo 18%; Merck Animal Health, Madison, NJ) alone or in combination with transdermal flunixin (BANAMINE Transdermal Pour-on Solution; Merck Animal Health, Madison, NJ) on arrival at the feedlot. Three hundred eighty-four polled, Continental × English, and English crossbred bulls (n = 199) and steers (n = 185) were enrolled into one of two treatments: 1) tildipirosin administered in the neck as a single dose of 4 mg/kg only (PLBO) 2) tildipirosin in combination with transdermal flunixin applied to the dorsal midline at a dose of 3.3 mg/kg (FTD). Outcomes measured were average daily gain (ADG), dry mater intake (DMI), gain to feed, morbidity, mortality, accelerometer activity data, and a daily visual analog scale (VAS) assessment of well-being. Body weight (BW) was determined by weighing individual animals; ADG was calculated as initial BW-final BW / total days on feed; DMI was calculated as daily pen feed allocation-feed remaining at next feeding / number of calves in the pen; and gain to feed was calculated as pen level ADG / pen level DMI. The VAS used was a 100 mm line anchored at each end by descriptors of "no pain" or "severe pain". Statistical analysis was performed using JMP 13 computer software using pen as the experimental unit, lot number as a random variable, and treatment as a fixed variable. There was no treatment effect on DMI (P = 0.51). During the first 14 d on feed, FTD calves had a lower ADG of 0.90 kg/d compared with 1.33 kg/d in the PLBO group (P = 0.05). There were no differences observed in morbidity and mortality between groups (P = 0.29). There were no treatment differences from activity data (P = 0.19). The VAS assessment showed a significant time × treatment interaction (P < 0.001). During the first 36 h after treatment administration, the FTD-treated calves had lower VAS scores [6.23 (95% CI: 5.27-7.20) compared with 7.28 (95% CI: 6.32-8.24)] than PLBO (P < 0.05). Results suggest that FTD-treated calves showed less signs of pain the first 36 h postdrug application relative to PLBO calves.

Effect of rain on absorption after transdermal application of flunixin in calves

Flunixin is a nonsteroidal anti‐inflammatory drug (NSAID) that has anti‐inflammatory, anti‐pyretic, and analgesic effects. Recently, a novel transdermal formulation was developed (Finadyne^® Transdermal, MSD Animal Health) and is now the first NSAID registered to be administered as a pour‐on product in cattle. According to the manufacturer's instructions, the pour‐on product should be applied only to dry skin and exposure to rain should be avoided for at least 6 hr after application. The objective of the study was to evaluate the effect of simulated exposure to light or heavy rain on flunixin absorption and bioavailability within the first 4 hr after administration. Therefore, an isocratic HPLC method was developed to quantify flunixin concentrations in bovine serum by UV detection. Light rain decreased flunixin absorption only when rain started immediately after flunixin administration, while light rain starting more than 30 min after administration of flunixin had no effect on absorption. Absorption and bioavailability of flunixin was impacted under simulated heavy rain conditions, when exposure to rain occurred within one hour after the application of the pour‐on formulation, but not later.

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.

The impact of pain on the pharmacokinetics of transdermal flunixin meglumine administered at the time of cautery dehorning in Holstein calves

OBJECTIVE

To study the influence of pain on the pharmacokinetics and anti-inflammatory actions of transdermal flunixin administered at dehorning.

STUDY DESIGN

Prospective, crossover, clinical study.

ANIMALS

A total of 16 male Holstein calves, aged 6-8 weeks weighing 61.3 ± 6.6 kg.

METHODS

Calves were randomly assigned to one of two treatments: transdermal flunixin and dehorning (PAIN) or transdermal flunixin and sham dehorning (NO PAIN). Flunixin meglumine (3.33 mg kg^-1) was administered topically as a pour-on concurrently with hot iron dehorning or sham dehorning. The calves were subjected to the alternative treatment 14 days later. Blood samples were collected at predetermined time points up to 72 hours for measurement of plasma flunixin concentrations. Pharmacokinetics parameters were determined using noncompartmental analysis. Prostaglandin E₂ (PGE₂) concentration was determined using a commercial enzyme-linked immunosorbent assay. The 80% inhibition concentration (IC₈₀) of PGE₂ was determined using nonlinear regression. Pharmacokinetic data were statistically analyzed using paired t tests and Wilcoxon rank sums for nonparametric data. Flunixin and PGE₂ concentrations were log transformed and analyzed using repeated measures.

RESULTS

A total of 15 calves completed the study. Plasma half-life of flunixin was significantly longer in PAIN (10.09 hours) than NO PAIN (7.16 hours) (p = 0.0202). Bioavailability of transdermal flunixin was 30% and 37% in PAIN and NO PAIN, respectively (p = 0.097). Maximum plasma concentrations of flunixin were 0.95 and 1.16 μg mL^-1 in PAIN and NO PAIN, respectively (p = 0.089). However, there was a treatment (PAIN versus NO PAIN) by time interaction (p = 0.0353). PGE₂ concentrations were significantly lower in the PAIN treatment at 48 and 72 hours (p = 0.0092 and p = 0.0287, respectively). The IC₈₀ of PGE₂ by flunixin was similar in both treatments (p = 0.88).

CONCLUSION AND CLINICAL RELEVANCE

Pain alters the pharmacokinetics and anti-inflammatory effects of transdermally administered flunixin.