Effects of transdermal flunixin meglumine on pain biomarkers at dehorning in calves

The objective of this study was to evaluate the analgesic properties of transdermal flunixin meglumine when given at the time of dehorning on pain biomarkers. Twenty-four weaned male Holstein calves, 6 to 8 wk of age were enrolled into the study. The calves were randomly assigned to 1 of 3 treatment groups: 1) transdermal flunixin and dehorn (DH-FLU); 2) transdermal flunixin and sham dehorn (SHAM-FLU); and 3) placebo and dehorn (DH-PLBO). Transdermal flunixin at a label dose of 3.33 mg/kg (or placebo at an equivalent volume) was administered as a pour-on along the top-line of the calves in each treatment group concurrently with electrocautery dehorning or sham dehorning. Biomarker parameters collected and analyzed included: infrared thermography (IRT), mechanical nociception threshold (MNT), plasma cortisol, and substance P (SP). There were no differences in maximal temperatures detected for the IRT measurements of the medial canthus of the eye for the DH groups. Mean control point MNT measurements at 48 h were 3.14 kgF, 3.46 kgF, and 1.43 kgF for the DH-FLU, Sham-FLU, and DH-PLBO groups, respectively (P = 0.0001). No other differences of MNT were detected between the dehorned groups for the other test sites and time points. Plasma cortisol reached peak concentration at 20 min postdehorning for the DH-FLU and DH-PLBO groups and 10 min for SHAM-FLU group. Peak plasma cortisol concentrations were 32.0 ng/mL, 12.7 ng/mL, and 28.8 ng/mL for the DH-FLU, SHAM-FLU, and DH-PLBO groups, respectively. Cortisol concentrations were lower for the DH-FLU group at 90 min postdehorning compared to the SHAM-FLU and DH-PLBO groups ( = 0.04). Area under the effect curve (AUEC) were similar for all groups ( = 0.93). No statistical differences in SP concentrations between groups were detected for any of the time points. In conclusion, transdermal flunixin meglumine given at the time of dehorning did not provide substantial analgesia based on the pain biomarkers investigated. Further investigation into its role as part of a multimodal analgesic plan is warranted.

Impact of carprofen administration on stress and nociception responses of calves to cautery dehorning

The objective of this study was to investigate the effects of carprofen administered immediately before cautery dehorning on nociception and stress. Forty Holstein calves aged approximately 6 to 8 wk old were either placebo treated and sham dehorned ( = 10) or cautery dehorned following administration of carprofen (1.4 mg/kg) subcutaneously ( = 10) or orally ( = 10) or a subcutaneous and oral placebo ( = 10) in a randomized, controlled trial. All animals were given a cornual nerve block using lidocaine before dehorning. Response variables including mechanical nociception threshold, ocular temperature, heart rate, and respiratory rate were measured before and following cautery dehorning for 96 h. Blood samples were also collected over 96 h following dehorning and analyzed for plasma cortisol and substance P concentrations by RIA. Plasma carprofen concentration and ex vivo PGE concentrations were also determined for this time period. Average daily gain was calculated for 7 d after dehorning. Data were analyzed using a linear mixed effects model with repeated measures, controlling for baseline values by their inclusion as a covariate in addition to planned contrasts. Dehorning was associated with decreased nociception thresholds throughout the study and a stress response immediately after dehorning, following the loss of local anesthesia, and 48 h after dehorning compared with sham-dehorned calves. Carprofen was well absorbed after administration and reached concentrations that inhibited ex vivo PGE concentrations for 72 h (subcutaneous) and 96 h (oral) compared with placebo-treated calves ( < 0.05). Carprofen-treated calves tended to be less sensitive ( = 0.097) to nociceptive threshold tests. Overall, at the dosing regimen studied, the effect of carprofen on sensitivity and stress following cautery dehorning was minimal. Consideration of route of administration and dose determination studies may be warranted.

The pharmacokinetics of transdermal flunixin meglumine in Holstein calves

This study describes the pharmacokinetics of topical and intravenous (IV) flunixin meglumine in Holstein calves. Eight male Holsteins calves, aged 6 to 8 weeks, were administered flunixin at a dose of 2.2 mg/kg intravenously. Following a 10-day washout period, calves were dosed with flunixin at 3.33 mg/kg topically (transdermal). Blood samples were collected at predetermined times from 0 to 48 h for the intravenous portions and 0 to 72 h following topical dosing. Plasma drug concentrations were determined using liquid chromatography with mass spectroscopy. Pharmacokinetic analysis was completed using noncompartmental methods. The mean bioavailability of topical flunixin was calculated to be 48%. The mean AUC for flunixin was determined to be 13.9 h × ug/mL for IV administration and 10.1 h × ug/mL for topical administration. The mean half-life for topical flunixin was 6.42 h and 4.99 h for the intravenous route. The C_max following topical application of flunixin was 1.17 μg/mL. The time to maximum concentration was 2.14 h. Mean residence time (MRT) following IV injection was 4.38 h and 8.36 h after topical administration. In conclusion, flunixin when administered as a topical preparation is rapidly absorbed and has longer half-life compared to IV administration.

The effects of firocoxib on cautery disbudding pain and stress responses in preweaned dairy calves

Perioperative analgesic effects of oral firocoxib following cautery disbudding were investigated in preweaned calves. Twenty Holstein calves approximately 4 to 6wk old received a single oral dose of firocoxib, a nonsteroidal antiinflammatory, at 0.5mg/kg (n=10) or placebo (n=10) in a randomized controlled clinical trial. Responses, including ocular temperature determined by infrared thermography, pressure algometry measuring mechanical nociception threshold, and heart rate, were evaluated at 2, 4, 7, 8, and 24h after cornual nerve block and cautery disbudding. Blood samples were collected over 96h and analyzed for plasma cortisol and substance P concentrations by RIA. Additionally, ex vivo prostaglandin E2 concentrations were determined over a 72-h study period using an enzyme immunoassay. Data were analyzed using a linear mixed effects model with repeated measures. An inhibition of ex vivo prostaglandin E2 synthesis was observed from 12 to 48h following disbudding in calves treated with firocoxib. Cautery disbudding was associated with an increased nociception for the duration of sampling (24h). During the initial 24-h period following disbudding, no difference in response between treatment groups was noted. Following 24h, mean cortisol concentrations diverged between the 2 study groups with placebo-treated calves having increased cortisol concentrations at approximately 48h after disbudding. Furthermore, the overall integrated cortisol response as calculated as area under the effect curve tended to be reduced in firocoxib-treated calves. The prolonged effects of cautery dehorning require further investigation. Moreover, the effect of firocoxib on cortisol reduction observed in this study requires additional exploration.