Enantiospecific pharmacokinetics and pharmacodynamics of ketoprofen in sheep

Pharmacokinetic/pharmacodynamic modeling of ketoprofen and flunixin at piglet castration and tail-docking

This study performed population‐pharmacokinetic/pharmacodynamic (pop‐PK/PD) modeling of ketoprofen and flunixin in piglets undergoing routine castration and tail‐docking, utilizing previously published data. Six‐day‐old male piglets (8/group) received either ketoprofen (3.0 mg/kg) or flunixin (2.2 mg/kg) intramuscularly. Two hours post‐dose, piglets were castrated and tail docked. Inhibitory indirect response models were developed utilizing plasma cortisol or interstitial fluid prostaglandin E2 (PGE2) concentration data. Plasma IC50 for ketoprofen utilizing PGE2 as a biomarker was 1.2 μg/ml, and ED50 for was 5.83 mg/kg. The ED50 calculated using cortisol was 4.36 mg/kg; however, the IC50 was high, at 2.56 μg/ml. A large degree of inter‐individual variability (124.08%) was also associated with the cortisol IC50 following ketoprofen administration. IC50 for flunixin utilizing cortisol as a biomarker was 0.06 μg/ml, and ED50 was 0.51 mg/kg. The results show that the currently marketed doses of ketoprofen (3.0 mg/kg) and flunixin (2.2 mg/kg) correspond to drug responses of 33.97% (ketoprofen‐PGE2), 40.75% (ketoprofen‐cortisol), and 81.05% (flunixin‐cortisol) of the maximal possible responses. Given this information, flunixin may be the best NSAID to use in mitigating castration and tail‐docking pain at the current label dose.

The Surface Area to Volume Ratio Changes the Pharmacokinetic and Pharmacodynamic Parameters in the Subcutaneous Tissue Cage Model: As Illustrated by Carprofen in Sheep

Introduction

Pharmacokinetic and pharmacodynamic models can be powerful tools for predicting outcomes. Many models are based on repetitive sampling of the vascular space, due to the simplicity of obtaining samples. As many drugs do not exert their effect in the vasculature, models have been developed to sample tissues outside the bloodstream. Tissue cages are hollow devices implanted subcutaneously, or elsewhere, that are filled with fluid allowing repetitive sampling to occur. The physical dimensions of the cage, namely, the diffusible surface area to volume ratio, would be expected to change the rate of drug movement into and out of tissue cages.

Methods

Seven sheep were implanted with five pairs of tissue cages, subcutaneously. Each pair of cages had a different length but a fixed diffusible surface area, so the surface area to volume ratio differed. Carrageenan was injected into half of the cages in each animal during one sampling period in a cross-over design. Samples from each cage and the bloodstream were obtained at 14-time points during two sampling periods. The concentration of carprofen was measured using LC–MS/MS and the results were modeled using nonlinear mixed-effects techniques. Prostaglandin metabolites were also measured and the change over time was analyzed using linear mixed effect modeling.

Results

The presence of carrageenan within an animal changed the systemic pharmacokinetics of carprofen. The rate of drug movement into and out of the tissue cages varied with the surface area to volume ratio. The concentration time curve for prostaglandin metabolites changed with cage size.

Conclusion

The surface area volume ratio of tissue cages will influence the calculated pharmacokinetic parameters and may affect calculated pharmacodynamics, thus, it is an important factor to consider when using tissue cage data for dosing regimes.

Cardiorespiratory alterations in a newborn ovine model of systemic viral inflammation

BACKGROUND

Respiratory viruses can be responsible for severe apneas and bradycardias in newborn infants. The link between systemic inflammation with viral sepsis and cardiorespiratory alterations remains poorly understood. We aimed to characterize these alterations by setting up a full-term newborn lamb model of systemic inflammation using polyinosinic:polycytidylic acid (Poly I:C).

METHODS

Two 6-h polysomnographic recordings were carried out in eight lambs on two consecutive days, first after an IV saline injection, then after an IV injection of 300 μg/kg Poly I:C.

RESULTS

Poly I:C injection decreased locomotor activity and increased NREM sleep. It also led to a biphasic increase in rectal temperature and heart rate. The latter was associated with an overall decrease in heart-rate variability, with no change in respiratory-rate variability. Lastly, brainstem inflammation was found in the areas of the cardiorespiratory control centers 6 h after Poly I:C injection.

CONCLUSIONS

The alterations in heart-rate variability induced by Poly I:C injection may be, at least partly, of central origin. Meanwhile, the absence of alterations in respiratory-rate variability is intriguing and noteworthy. Although further studies are obviously needed, this might be a way to differentiate bacterial from viral sepsis in the neonatal period.

IMPACT

Provides unique observations on the cardiorespiratory consequences of injecting Poly I:C in a full-term newborn lamb to mimic a systemic inflammation secondary to a viral sepsis. Poly I:C injection led to a biphasic increase in rectal temperature and heart rate associated with an overall decrease in heart-rate variability, with no change in respiratory-rate variability. Brainstem inflammation was found in the areas of the cardiorespiratory control centers.

Pharmacokinetics and Bioavailability of Carprofen in Rainbow Trout (Oncorhynchus mykiss) Broodstock

The aim of this study was to determine the pharmacokinetics of carprofen following intravenous (IV), intramuscular (IM) and oral routes to rainbow trout (Oncorhynchus mykiss) broodstock at temperatures of 10 ± 1.5 °C. In this study, thirty-six healthy rainbow trout broodstock (body weight, 1.45 ± 0.30 kg) were used. The plasma concentrations of carprofen were determined using high-performance liquid chromatography and pharmacokinetic parameters were calculated using non-compartmental analysis. Carprofen was measured up to 192 h for IV route and 240 h for IM, and oral routes in plasma. The elimination half-life (t1/2λz) was 30.66, 46.11, and 41.08 h for IV, IM and oral routes, respectively. Carprofen for the IV route showed the total clearance of 0.02 L/h/kg and volume of distribution at steady state of 0.60 L/kg. For IM and oral routes, the peak plasma concentration (Cmax) was 3.96 and 2.52 μg/mL with the time to reach Cmax of 2 and 4 h, respectively. The bioavailability was 121.89% for IM route and 78.66% for oral route. The favorable pharmacokinetic properties such as the good bioavailability and long t1/2λz for IM and oral route of carprofen suggest the possibility of its effective use for the treatment of various conditions in broodstock.

Pharmacokinetics of Ketoprofen in Nile Tilapia (Oreochromis niloticus) and Rainbow Trout (Oncorhynchus mykiss)

The objective of this study was to document the pharmacokinetics of ketoprofen following 3 mg/kg intramuscular (IM) and intravenous (IV) injections in rainbow trout (Oncorhynchus mykiss) and 8 mg/kg intramuscular (IM) injection in Nile tilapia (Oreochromis niloticus). Plasma was collected laterally from the tail vein for drug analysis at various time intervals up to 72 h following the injection of ketoprofen. In trout, area under the curve (AUC) levels were 115.24 μg hr/mL for IM and 135.69 μg hr/mL for IV groups with a half-life of 4.40 and 3.91 h, respectively. In both trout and tilapia, there were detectable ketoprofen concentrations in most fish for 24 h post-injection. In tilapia, there was a large difference between the R- and S-enantiomers, suggesting either chiral inversion from R- to S-enantiomer or more rapid clearance of the R-enantiomer. AUC values of the S- and R-enantiomers were 510 and 194 μg hr/Ml, respectively, corresponding to a faster clearance for the R-enantiomer. This study shows that there were very high plasma concentrations of ketoprofen in trout and tilapia with no adverse effects observed. Future studies on the efficacy, frequency of dosing, analgesia, adverse effects, and route of administration are warranted.

Randomised trial of the bioavailability and efficacy of orally administered flunixin, carprofen and ketoprofen in a pain model in sheep

OBJECTIVE

To determine the efficacy and bioavailability of non-steroidal anti-inflammatory drugs (NSAIDs) when administered orally to sheep.

DESIGN

Randomised experimental design with four treatment groups: three NSAID groups and one control group (n = 10/group). The study animals were 40 18-month-old Merino ewes with an average weight of 31.4 ± 0.5 kg.

METHODS

Treatment was given orally at 24 h intervals for 6 days at dose rates expected to achieve therapeutic levels in sheep: carprofen (8.0 mg/kg), ketoprofen (8.0 mg/kg) and flunixin (4.0 mg/kg). Oil of turpentine (0.1 mL) was injected into a forelimb of each sheep to induce inflammation and pain; responses (force plate pressure, skin temperature, limb circumference, haematology and plasma cortisol) were measured at 0, 3, 6, 9, 12, 24, 36, 48, 72 and 96 h post-injection. NSAID concentrations were determined by ultra-high-pressure liquid chromatography.

RESULTS

The NSAIDs were detectable in ovine plasma 2 h after oral administration, with average concentrations of 4.5-8.4 µg/mL for ketoprofen, 2.6-4.1 µg/mL for flunixin and 30-80 µg/mL for carprofen. NSAID concentrations dropped 24 h after administration. Pain response to an oil of turpentine injection was assessed using the measures applied but no effect of the NSAIDs was observed. Although this pain model has been previously validated, the responses observed in this study differed from those in the previous study.

CONCLUSIONS AND CLINICAL RELEVANCE

The three NSAIDs reached inferred therapeutic concentrations in blood at 2 h after oral administration. The oil of turpentine lameness model may need further validation.

Preparation and the biopharmaceutical evaluation for the metered dose transdermal spray of dexketoprofen

The objective of the present work was to develop a metered dose transdermal spray (MDTS) formulation for transdermal delivery of dexketoprofen (DE). DE release from a series of formulations was assessed in vitro. Various qualitative and quantitative parameters like spray pattern, pump seal efficiency test, average weight per metered dose, and dose uniformity were evaluated. The optimized formulation with good skin permeation and an appropriate drug concentration and permeation enhancer (PE) content was developed incorporating 7% (w/w, %) DE, 7% (v/v, %) isopropyl myristate (IPM), and 93% (v/v, %) ethanol. In vivo pharmacokinetic study indicated that the optimized formulation showed a more sustainable plasma-concentration profile compared with the Fenli group. The antiinflammatory effect of DE MDTS was evaluated by experiments involving egg-albumin-induced paw edema in rats and xylene-induced ear swelling in mice. Acetic acid-induced abdominal constriction was used to evaluate the anti-nociceptive actions of DE MDTS. Pharmacodynamic studies indicated that the DE MDTS has good anti-inflammatory and anti-nociceptive activities. Besides, skin irritation studies were performed using rat as an animal model. The results obtained show that the MDTS can be a promising and innovative therapeutic system used in transdermal drug delivery for DE.

Pharmacodynamics, Chiral Pharmacokinetics, and Pharmacokinetic-Pharmacodynamic Modeling of Fenoprofen in Patients With Diabetes Mellitus

The objective of the present study was to assess the influence of type 1 and type 2 diabetes mellitus on the enantioselective pharmacodynamics and pharmacokinetics of fenoprofen. Patients with diabetes mellitus type 1 (n = 7) or type 2 (n = 7) and healthy volunteers (n = 13) received orally a single 600-mg dose of racemic fenoprofen. Monocompartmental analysis of (+)-(S)-fenoprofen showed a significant difference (P < .05, Kruskal-Wallis test) in area under the curve (AUC) values (153.68 vs 243.50 microg x h/mL) and oral clearance (1.95 vs 1.23 L/h) only between patients with diabetes mellitus type 2 and healthy volunteers. The inhibitory activity of cyclooxygenases was evaluated indirectly by the determination of prostaglandin E2 (COX-2) and thromboxane B2 (COX-1) using the sigmoidal inhibitory Emax model. The patients with type 2 diabetes mellitus presented lower IC50 (3.29 vs 6.0 microg/mL) and g (0.73 vs 2.01) values for COX-1 activity compared to healthy volunteers (P < .05, Kruskal-Wallis test). These results show that diabetes mellitus type 2, but not type 1, influences the pharmacokinetics and pharmacodynamics of (+)-(S)-fenoprofen.

Enantiospecific ketoprofen concentrations in plasma after oral and intramuscular administration in growing pigs

Background

Ketoprofen is a non-steroidal anti-inflammatory drug which has been widely used for domestic animals. Orally administered racemic ketoprofen has been reported to be absorbed well in pigs, and bioavailability was almost complete. The objectives of this study were to analyze R- and S-ketoprofen concentrations in plasma after oral (PO) and intra muscular (IM) routes of administration, and to assess the relative bioavailability of racemic ketoprofen for both enantiomers between those routes of administration in growing pigs.

Methods

Eleven pigs received racemic ketoprofen at dose rates of 4 mg/kg PO and 3 mg/kg IM in a randomized, crossover design with a 6-day washout period. Enantiomers were separated on a chiral column and their concentrations were determined by liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were calculated and relative bioavailability (F_rel) was determined for S and R –ketoprofen.

Results

S-ketoprofen was the predominant enantiomer in pig plasma after administration of the racemic mixture via both routes. The mean (± SD) maximum S-ketoprofen concentration in plasma (7.42 mg/L ± 2.35 in PO and 7.32 mg/L ± 0.75 in IM) was more than twice as high as that of R-ketoprofen (2.55 mg/L ± 0.99 in PO and 3.23 mg/L ± 0.70 in IM), and the terminal half-life was three times longer for S-ketoprofen (3.40 h ± 0.91 in PO and 2.89 h ± 0.85 in IM) than R-ketoprofen (1.1 h ± 0.90 in PO and 0.75 h ± 0.48 in IM). The mean (± SD) relative bioavailability (PO compared to IM) was 83 ± 20% and 63 ± 23% for S-ketoprofen and R-ketoprofen, respectively.

Conclusions

Although some minor differences were detected in the ketoprofen enantiomer concentrations in plasma after PO and IM administration, they are probably not relevant in clinical use. Thus, the pharmacological effects of racemic ketoprofen should be comparable after intramuscular and oral routes of administration in growing pigs.

Dose-response investigation of oral ketoprofen in pigs challenged with Escherichia coli endotoxin

In order to determine the effective dose, the effects of orally administered ketoprofen were evaluated in pigs following intravenous challenge with Escherichia coli endotoxin. One hour after the challenge, five groups of pigs were treated with either tap water or ketoprofen (0.5 mg/kg, 1 mg/kg, 2 mg/kg or 4 mg/kg). The body temperature was measured and a total clinical score was calculated after assessing the general behaviour, respiratory rate and locomotion of the pigs. Thromboxane B(2) and ketoprofen concentrations were analysed from blood samples. Ketoprofen treatment significantly reduced the rectal temperature and total clinical scores, and lowered blood thromboxane B(2) concentrations when compared with the control group. Ketoprofen plasma concentrations were lower than previously reported in healthy pigs after similar doses. The appropriate dose of orally administered ketoprofen in pigs in this model is 2 mg/kg, as the higher dose of 4 mg/kg failed to provide an additional benefit.

Chiral inversion of R(-) to S(+) ketoprofen in pigs

The S(+) enantiomer of ketoprofen is predominant in the plasma of pigs after administration of racemic ketoprofen, although the occurrence and extent of R(-)-to-S(+) inversion is uncertain. Plasma concentrations of both enantiomers were measured and percentages of S(+) ketoprofen were calculated at different time points after intravenous and oral dosing of pigs with 1.5mg/kg R(-) ketoprofen. S(+) ketoprofen was formed immediately after administration and concentrations exceeded R(-) concentrations after 1h. Absence of pre-systemic inversion was deduced from the lower S(+) percentages after oral administration. A rapid and increasing inversion, reaching a maximum of about 70%, occurred and appeared to be responsible for the predominance of S(+) ketoprofen in pig plasma after administration of the racemate.

Development and validation of a tissue cage model of acute inflammation in the cat

Four cylindrical silicon tissue cages (TC, internal volume: 6.7 ± 0.11 cm(3)) were inserted subcutaneously in 29 young healthy cats. A mild inflammatory reaction was induced by intracaveal injection of 1 mL of a 2%λ-carrageenan solution. TC exudate was subsequently sampled at predetermined times (up to 120 h) to measure exudate leucocyte counts and the concentrations of protein and eicosanoids. TC remained in situ for 9-10 months and were well tolerated. Leucocyte counts peaked at 34 h (50.1 ± 57.6 × 10(3) cells/mm(3) ) and returned towards baseline after 72 h. Protein concentration increased from 26.2 ± 2.7 g/L to a peak of 35.9 ± 6.0 g/L at 12 h before returning to baseline at 48 h. Exudate prostaglandin (PG)E(2) concentration peaked at 24 h (11.7 ± 13.7 ng/mL) and returned to baseline by 120 h. Repeated collection of fluid from noninjected cages did not increase transudate PGE(2). Ketoprofen (2 mg/kg, subcutaneously) suppressed exudate PGE(2) at 24 h. The carrageenan-stimulated TC model is an ethical and novel means of investigating soft tissue inflammation in the cat, in which exudate PGE(2) acts as surrogate marker of cyclooxygenase-2 activity. This model will facilitate the investigation of in vivo pharmacokinetics and pharmacodynamics of anti-inflammatory drugs in this species.

Enantioselective pharmacokinetics of ketoprofen in piglets: the significance of neonatal age

Following intravenous dose of 6mg/kg racemic ketoprofen, the chiral pharmacokinetics of ketoprofen was investigated in eight piglets aged 6 and 21days old. S-ketoprofen predominated over R-ketoprofen in plasma of the piglets in both age groups. The volumes of distribution of S-ketoprofen for the 6- and 21-day-old piglets were 241.7 (211.3-276.5) mL/kg and 155.0 (138.7-173.1) mL/kg, respectively, while the corresponding parameters for R-ketoprofen were 289.2 (250.3-334.2) mL/kg and 193.0 (168.7-220.8) mL/kg. The clearances of R-ketoprofen [948.4 (768.0-1171.2) mL/h/kg and 425 (319.1-566.0) mL/h/kg for the 6- and 21-day-old piglets, respectively] were significantly higher compared to the clearances of S-ketoprofen [57.3 (46.6-70.4) mL/h/kg and 33.8 (27.0-42.2) mL/h/kg for 6- and 21-day-old piglets, respectively]. The elimination half-life of S-ketoprofen was 3.4h for both age groups, while the elimination half-life of R-ketoprofen was 0.2h for the 6-day-old and 0.4h for the 21-day-old piglets. The clearances of both R- and S-ketoprofen were significantly higher in the 6-day-old piglets compared to when they were 21 days old. Furthermore, the volumes of distribution were larger in the youngest age group.

Early detection of ketoprofen-induced acute kidney injury in sheep as determined by evaluation of urinary enzyme activities

OBJECTIVE

To evaluate early indicators of renal tissue destruction and changes in urinary enzyme activities in sheep during the first hours after acute kidney injury induced by administration of an overdose of an NSAID.

ANIMALS

12 adult female sheep.

PROCEDURES

Acute kidney injury was induced in 6 sheep by administration of ketoprofen (30 mg/kg, IV) and detected by evaluation of urinary protein concentration, iohexol clearance, and results of histologic examination. Six sheep served as control animals. Blood and urine samples were collected for up to 24 hours after administration of ketoprofen. Plasma concentrations of urea, creatinine, albumin, and total protein; plasma activities of alkaline phosphatase, acid phosphatase, γ-glutamyl transpeptidase (GGT), matrix metalloproteinase (MMP)-2, and MMP-9; and urinary creatinine and protein concentrations, specific gravity, and activities of alkaline phosphatase, acid phosphatase, GGT lactate dehydrogenase, N-acetyl-β-D-glucosaminidase (NAG), MMP-2, and MMP-9 were measured. Urinary protein concentration and enzyme activities were normalized on the basis of urinary creatinine concentrations and reported as ratios.

RESULTS

Many urinary enzyme-to-creatinine ratios increased before the plasma creatinine concentration exceeded the reference value. Urine NAG, lactate dehydrogenase, and acid phosphatase activities were increased beginning at 2 hours after ketoprofen administration, and alkaline phosphatase, GGT, and MMP-2 activities were increased beginning at 4 hours after ketoprofen administration. Most peak urinary enzyme-to-creatinine ratios were detected earlier than were the highest plasma creatinine and urea concentrations.

CONCLUSIONS AND CLINICAL RELEVANCE

Urinary enzyme activities were sensitive early indicators of acute kidney injury induced by an overdose of an NSAID in sheep.

Ketoprofen in piglets: enantioselective pharmacokinetics, pharmacodynamics and PK/PD modelling

The chiral pharmacokinetics and pharmacodynamics of ketoprofen were investigated in a placebo-controlled study in piglets after intramuscular administration of 6 mg/kg racemic ketoprofen. The absorption half-lives of both enantiomers were short, and S-ketoprofen predominated over R-ketoprofen in plasma. A kaolin-induced inflammation model was used to evaluate the anti-inflammatory, antipyretic and analgesic effects of ketoprofen. Skin temperatures increased after the kaolin injection, but the effect of ketoprofen was small. No significant antipyretic effects could be detected, but body temperatures tended to be lower in the ketoprofen-treated piglets. Mechanical nociceptive threshold testing was used to evaluate the analgesic effects. The piglets in the ketoprofen-treated group had significantly higher mechanical nociceptive thresholds compared to the piglets in the placebo group for 12-24 h following the treatment. Pharmacokinetic/pharmacodynamic modelling of the results from the mechanical nociceptive threshold testing gave a median IC(50) for S-ketoprofen of 26.7 μg/mL and an IC(50) for R-ketoprofen of 1.6 μg/mL. This indicates that R-ketoprofen is a more potent analgesic than S-ketoprofen in piglets. Estimated ED(50) for racemic ketoprofen was 2.5 mg/kg.

Use of a pharmacokinetic/pharmacodynamic approach in the cat to determine a dosage regimen for the COX-2 selective drug robenacoxib

This study investigated the analgesic, anti-inflammatory and antipyretic efficacy of the new COX-2 selective inhibitor robenacoxib in the cat and established pharmacodynamic (PD) parameters for these effects. Robenacoxib, at a dosage of 2 mg/kg administered subcutaneously, was evaluated in a kaolin-induced paw inflammation model in 10 cats, using both clinically relevant endpoints (lameness scoring, locomotion tests) and other indicators of inflammation (body and skin temperature, thermal pain threshold) to establish its pharmacological profile. A pharmacokinetic/pharmacodynamic (PK/PD) modelling approach, based on indirect response models, was used to describe the time course and magnitude of the responses to robenacoxib. All endpoints demonstrated good responsiveness to robenacoxib administration and both the magnitude and time courses of responses were well described by the indirect pharmacodynamic response models. Pharmacokinetic and clinically relevant pharmacodynamic parameters were used to simulate dosage regimens that will assist the planning of clinical trials and the selection of an optimal dosage regimen for robenacoxib in the cat.

Differential inhibition of cyclooxygenase isoenzymes in the cat by the NSAID robenacoxib

Robenacoxib is a new nonsteroidal anti-inflammatory drug (NSAID) developed for use in companion animal medicine. The objectives of this study were: to quantify the inhibitory actions of robenacoxib on cyclooxygenase (COX) isoenzymes in feline whole blood assays; to establish blood concentration-time profiles of robenacoxib after intravenous and subcutaneous dosing in the cat and; to predict the time courses of inhibition of COX isoforms by robenacoxib. COX-1 and COX-2 activities in heparinized feline whole blood samples were induced with calcium ionophore and lipopolysaccharide, respectively. Inhibition of thromboxane B2 provided a marker of both COX-1 and COX-2 activities and a nonlinear parametric mixed effects modelling approach was used to establish the pharmacodynamic parameters describing this inhibition. Mean values (and prediction intervals) of IC50 were 28.9 (16.4-51.1) microM (COX-1) and 0.058 (0.010-0.340) microM (COX-2). These parameters were used to compute several selectivity indices. Selectivity IC ratios (COX-1:COX-2) were 502.3 (IC50/IC50), 451.6 (IC95/IC95) and 17.05 (IC20/IC80). Based on a clinically recommended dosage regimen of 2 mg/kg, it was predicted that the corresponding mean robenacoxib blood concentration over the first 12 h after drug administration corresponded to 5% inhibition of COX-1 and 90% inhibition of COX-2.

Evaluation of bioequivalence after oral, intramuscular, and intravenous administration of racemic ketoprofen in pigs

OBJECTIVE

To assess bioequivalence after oral, IM, and IV administration of racemic ketoprofen in pigs and to investigate the bioavailability after oral and IM administration.

ANIMALS

8 crossbred pigs.

PROCEDURES

Each pig received 4 treatments in a randomized crossover design, with a 6-day washout period. Ketoprofen was administered at 3 and 6 mg/kg, PO; 3 mg/kg, IM; and 3 mg/kg, IV. Plasma ketoprofen concentrations were measured by use of high-performance liquid chromatography for up to 48 hours. To assess bioequivalence, a 90% confidence interval was calculated for the area under the time-concentration curve (AUC) and maximum plasma concentration (C(max)).

RESULTS

Equivalence was not detected in the AUCs among the various routes of administration nor in C(max) between oral and IM administration of 3 mg/kg. The bioavailability of ketoprofen was almost complete after each oral or IM administration. Mean +/- SD C(max) was 5.09 +/- 1.41 microg/mL and 7.62 +/- 1.22 microg/mL after oral and IM doses of 3 mg/kg, respectively. Mean elimination half-life varied from 3.52 +/- 0.90 hours after oral administration of 3 mg/kg to 2.66 +/- 0.50 hours after IV administration. Time to peak C(max) after administration of all treatments was approximately 1 hour. Increases in AUC and C(max) were proportional when the orally administered dose was increased from 3 to 6 mg/kg.

CONCLUSIONS AND CLINICAL RELEVANCE

Orally administered ketoprofen was absorbed well in pigs, although bioequivalence with IM administration of ketoprofen was not detected. Orally administered ketoprofen may have potential for use in treating pigs.

Effectiveness of non-steroidal anti-inflammatory drugs and epidural anaesthesia in reducing the pain and stress responses to a surgical husbandry procedure (mulesing) in sheep

In this study, we examined the potential of several widely used non-steroidal anti-inflammatory drugs (NSAIDs) and other analgesics to reduce pain and stress in sheep after surgery. Because mulesing involves a greater degree of tissue trauma than other surgical husbandry procedures such as castration or tail-docking, it provides a more rigorous and conservative test to identify potentially useful analgesic strategies in sheep. Merino lambs (5 weeks of age) were randomised into eight treatment groups: (1) carprofen; (2) flunixin; (3) ketoprofen; (4) buprenorphine; (5) xylazine; (6) lignocaine epidural; (7) saline control; (8) sham control. The NSAIDs were administered 1.5 h before mulesing, buprenorphine 0.75 h and xylazine and lignocaine 0.25 h before mulesing. Pain- and discomfort-related behaviours were recorded for 12 h after mulesing, and plasma cortisol concentrations were measured before mulesing and 0.5, 6, 12, 24 and 48 h after mulesing. The results indicated that no single analgesic treatment provided satisfactory analgesia during both the surgical mulesing procedure and the ensuing period of pain associated with the inflammatory phase. However, there were indications that two NSAIDs (carprofen and flunixin) showed good potential as analgesics during the inflammatory phase. A combination of short- and long-acting analgesics may be needed to provide more complete pain relief. In conclusion, the administration of some NSAIDs offers the potential for good analgesia in sheep for the inflammatory phase following the tissue trauma of surgical husbandry procedures. Other analgesic options need to be considered if the acute stress response to the procedure is to be reduced.

N-(6,7-Dichloro-2,3-dioxo-1,2,3,4-tetrahydroquinoxalin-5-yl)-N-alkylsulfonamides as peripherally restricted N-methyl-d-aspartate receptor antagonists for the treatment of pain

It has been hypothesized that peripherally restricted NMDA receptor antagonists may be effective analgesics for osteoarthritis pain. A class of novel quinoxalinedione atropisomers, first discovered for an NMDA receptor antagonist program for the treatment of stroke, was evaluated and further optimized with the goal of finding peripherally restricted NMDA receptor antagonists.

Involvement of opioidergic and alpha2-adrenergic mechanisms in the central analgesic effects of non-steroidal anti-inflammatory drugs in sheep

The level within the central nervous system where non-steroidal anti-inflammatory drugs (NSAIDs) produce analgesia and the mechanisms by which they mediate this effect are still uncertain. This study assessed the central analgesic effects of ketoprofen, phenylbutazone, salicylic acid and tolfenamic acid in sheep implanted with indwelling intrathecal (i.t.) catheters and submitted to mechanical noxious stimulation. The sheep received i.t. cumulative concentrations (0.375-200 microM; 100 microL) as well as a single intravenous (i.v.) dose (3, 8, 10 and 2 mg/kg, respectively) of each NSAID. The sheep were also given i.t. naloxone (5.49 mM; 100 microL) and atipamezole (4.03 mM; 100 microL) prior to i.v. ketoprofen. None of the i.t. NSAIDs increased mechanical thresholds. Intravenously, only ketoprofen and tolfenamic acid raised the pain thresholds. The hypoalgesic effect of i.v. ketoprofen was prevented by i.t. naloxone or atipamezole. Although NSAIDs had no direct effect on the spinal cord, their analgesic action appeared to be spinally mediated.

Pharmacodynamics and pharmacokinetics of nonsteroidal anti-inflammatory drugs in species of veterinary interest

This review summarises selected aspects of the pharmacokinetics (PK) and pharmacodynamics (PD) of nonsteroidal anti-inflammatory drugs (NSAIDs). It is not intended to be comprehensive, in that it covers neither minor species nor several important aspects of NSAID PD. The limited objective of the review is to summarise those aspects of NSAID PK and PD, which are important to an understanding of PK-PD integration and PK-PD modelling (the subject of the next review in this issue). The general features of NSAID PK are: usually good bioavailability from oral, intramuscular and subcutaneous administration routes (but with delayed absorption in horses and ruminants after oral dosing), a high degree of binding to plasma protein, low volumes of distribution, limited excretion of administered dose as parent drug in urine, marked inter-species differences in clearance and elimination half-life and ready penetration into and slow clearance from acute inflammatory exudate. The therapeutic effects of NSAIDs are exerted both locally (at peripheral inflammatory sites) and centrally. There is widespread acceptance that the principal mechanism of action (both PD and toxicodynamics) of NSAIDs at the molecular level comprises inhibition of cyclooxygenase (COX), an enzyme in the arachidonic acid cascade, which generates inflammatory mediators of the prostaglandin group. However, NSAIDs possess also many other actions at the molecular level. Two isoforms of COX have been identified. Inhibition of COX-1 is likely to account for most of the side-effects of NSAIDs (gastrointestinal irritation, renotoxicity and inhibition of blood clotting) but a minor contribution also to some of the therapeutic effects (analgesic and anti-inflammatory actions) cannot be excluded. Inhibition of COX-2 accounts for most and possibly all of the therapeutic effects of NSAIDs. Consequently, there has been an intensive search to identify and develop drugs with selectivity for inhibition of COX-2. Whole blood in vitro assays are used to investigate quantitatively the three key PD parameters (efficacy, potency and sensitivity) for NSAID inhibition of COX isoforms, providing data on COX-1:COX-2 inhibition ratios. Limited published data point to species differences in NSAID-induced COX inhibition, for both potency and potency ratios. Members of the 2-arylpropionate sub-groups of NSAIDs exist in two enantiomeric forms [R-(-) and S-(+)] and are licensed as racemic mixtures. For these drugs there are marked enantiomeric differences in PK and PD properties of individual drugs in a given species, as well as important species differences in both PK and PD properties.

PK-PD integration and PK-PD modelling of nonsteroidal anti-inflammatory drugs: principles and applications in veterinary pharmacology

Much useful information relevant to elucidation of mechanism of action of nonsteroidal anti-inflammatory drugs (NSAIDs) at the molecular level can be obtained from integrating pharmacokinetic (PK) and pharmacodynamic (PD) data, such data being obtained usually, although not necessarily, in separate studies. Integrating PK and PD data can also provide a basis for selecting clinically relevant dosing schedules for subsequent evaluation in disease models and clinical trials. The principles underlying and uses of PK-PD integration are illustrated in this review for phenylbutazone in the horse and cow, carprofen and meloxicam in the horse, carprofen and meloxicam in the cat and nimesulide in the dog. In the PK-PD modelling approach for NSAIDs, the PK and PD data are generated (usually though not necessarily) in vivo in the same investigation and then modelled in silico, usually using the integrated effect compartment or indirect response models. Drug effect is classically modelled with the sigmoidal E(max) (Hill) equation to derive PD parameters which define efficacy, potency and sensitivity. The PK-PD modelling approach for NSAIDs can be undertaken at the molecular level using surrogates of inhibition of cyclooxygenase (COX) isoforms (or indeed other enzymes e.g. 5-lipoxygenase). Examples are provided of the generation of PD parameters for several NSAIDs (carprofen, ketoprofen, vedaprofen, flunixin and tolfenamic acid) in species of veterinary interest (horse, calf, sheep and goat), which indicate that all drugs investigated except vedaprofen were non-selective for COX-1 and COX-2 in the four species investigated under the experimental conditions used, vedaprofen being a COX-1 selective NSAID. In these studies, plasma concentration was linked to COX inhibitory action in the biophase using an effect compartment model. Data for S-(+)-ketoprofen have been additionally subjected to inter-species modelling and allometric scaling of both PK and PD parameters. For several species values of four PK parameters were highly correlated with body weight, whilst values for PD parameters based on COX inhibition lacked allometric relationship with body weight. PK-PD modelling of NSAIDs has also been undertaken using clinical end-points and surrogates for clinical end-points in disease models. By measurement of clinically relevant indices in clinically relevant models, data generated for PD parameters have been used to set dosages and dose intervals for evaluation and confirmation in clinical trials. PK-PD modelling of NSAIDs is likely to prove superior to conventional dose titration studies for dosage schedule determination, as it sweeps the whole of the concentration-effect relationship for all animals and therefore permits determination of genuine PD parameters. It also introduces time as a second independent variable thus allowing prediction of dosage interval. Using indirect response models and clinically relevant indices, PD data have been determined for flunixin, phenylbutazone and meloxicam in the horse, nimesulide in the dog and meloxicam in the cat.

Pharmacology of drugs used to treat osteoarthritis in veterinary practice

As in humans, pain in animals may be associated with a wide range of conditions and circumstances, ranging from acute trauma to joint diseases. Joint diseases are common in companion animal medicine (horse, dog, cat) and at least 80% of cases are classified as osteoarthritis (OA). Several drug classes are available for OA therapy, including corticosteroids, non-steroidal antiinflammatory drugs (NSAIDs), agents with potential disease modifying properties and nutraceuticals. For long-term maintenance OA treatment, particularly in the horse and dog, NSAIDs are routinely and extensively used. This review outlines the pharmacokinetics (PK) and pharmacodynamics (PD) of NSAIDs in companion and farm animal species. NSAID PK and PD have been studied in models of acute inflammation, which enable use of PK-PD modeling to facilitate (a) studies of mechanism of action at the molecular level and (b) prediction of dosages for clinical use. The PK-PD approach is a powerful but underutilized tool which also facilitates inter-species comparisons.

Modeling and allometric scaling of s(+)-ketoprofen pharmacokinetics and pharmacodynamics: a retrospective analysis

Interspecies scaling of pharmacokinetic (PK) parameters is commonplace in drug development. However, information about proportionality of pharmacodynamic (PD) parameters in different species is scarce. We investigated the feasibility of allometric scaling of PK and PD parameters of s(+)-ketoprofen (sKTP) using the literature data from several animal species. Two different indirect response models were proposed to characterize sKTP inhibitory effects on synthesis of thromboxane B(2) (TXB(2)) and prostaglandin E(2) (PGE(2)). Using the traditional allometric approach, the obtained PK and PD parameters were plotted against body weights (BW) on a log-log scale. For all species, values of systemic clearance (Cl), distribution clearance (Cl(D)), central volume of distribution (V(c)), and volume of distribution at steady-state (V(ss)) were highly correlated (r(2) = 0.89-0.99) with BW. The PD parameters for inhibition of TXB(2) synthesis were poorly correlated with BW (r(2) = 0.25-0.54) while most of the parameters for inhibition of PGE(2) synthesis lacked any correlation (r(2) approximately 0.05). In conclusion, indirect response models adequately described the time course of sKTP inhibitory effects on synthesis of TXB(2) and PGE(2). Allometrical scaling showed PK parameters to change proportionally to BW, whereas PD parameters had limited ranges and were essentially weight independent.

Pharmacodynamics, chiral pharmacokinetics and PK-PD modelling of ketoprofen in the goat

There have been few studies of the pharmacodynamics of nonsteroidal antiinflammatory drugs (NSAIDs) using PK-PD modelling, yet this approach offers the advantage of defining the whole concentration-effect relationship, as well as its time course and sensitivity. In this study, ketoprofen (KTP) was administered intravenously to goats as the racemate (3.0 mg/kg total dose) and as the single enantiomers, S(+) KTP and R(-) KTP (1.5 mg/kg of each). The pharmacokinetics and pharmacodynamics of KTP were investigated using a tissue cage model of acute inflammation. The pharmacokinetics of both KTP enantiomers was characterized by rapid clearance, short mean residence time (MRT) and low volume of distribution. The penetration of R(-) KTP into inflamed (exudate) and noninflamed (transudate) tissue cage fluids was delayed but area under the curve values were only slightly less than those in plasma, whereas MRT was much longer. The S(+) enantiomer of KTP penetrated less readily into exudate and transudate. Unidirectional inversion of R(-) to S(+) KTP occurred. Both rac-KTP and the separate enantiomers produced marked inhibition of serum thromboxane B2 (TxB2) synthesis (ex vivo) and moderate inhibition of exudate prostaglandin E2 (PGE2) synthesis (in vivo); pharmacodynamic variables for S(+) KTP were Emax (%) = 94 and 100; IC50 (microg/mL) = 0.0033 and 0.0030; N = 0.45 and 0.58, respectively, where Emax is the maximal effect, IC50 the plasma drug concentration producing 50% of Emax and N the slope of log concentration/effect relationship. The IC50 ratio, serum TxB2:exudate PGE2 was 1.10. Neither rac-KTP nor the individual enantiomers suppressed skin temperature rise at, or leucocyte infiltration into, the site of acute inflammation. These data illustrate for KTP shallow concentration-response relationships, probable nonselectivity of KTP for cyclooxygenase (COX)-1 and COX-2 inhibition and lack of measurable effect on components of inflammation.

Tissue chamber model of acute inflammation in farm animal species

A tissue chamber model of acute inflammation for use in comparative studies in calves, sheep, goats and pigs has been established and validated. Tissue chambers were prepared from silicon rubber tubing, of inner diameter 12.7 mm, length 115 mm and volume 15 ml, with 10 holes, each of 6mm diameter, at each end. In each animal two or four chambers were inserted at subcutaneous sites. Six weeks after implantation an acute inflammatory reaction in a single cage was generated by the intracaveal injection of 0.5 ml of 1% carrageenan solution. Serial samples of exudate (injected chamber), transudate (non-injected chamber) and blood were collected for measurement of exudate and transudate leucocyte count, prostaglandin (PG)E(2) concentration in exudate and serum thromboxane (Tx)B(2) concentration. In addition, skin temperature changes over exudate and transudate chambers were recorded. In all four species, carrageenan induced an acute inflammatory response, indicated by increases to peak values followed by return towards baseline in skin temperature, leucocyte count and PGE(2) concentration. For each of these variables in calves, sheep and goats the increases were significantly greater for exudate than for transudate. The degree of intra-species variation in each variable was acceptable. Marked inter-species differences were recorded: skin temperature rise was greatest in calves and least in sheep and goats; exudate PGE(2) concentration was increased in the order sheep>goat>pig>calf; serum TxB(2) concentration was increased in the order calf>goat>sheep>pig and exudate leucocyte count was increased to a greater extent in the pig than in the three ruminant species. The model has advantages over some previously described tissue chamber models of inflammation and will be suitable for use in comparative studies of inflammatory mechanisms and the pharmacokinetics and pharmacodynamics of anti-inflammatory drugs.

Ketoprofen in the cat: pharmacodynamics and chiral pharmacokinetics

The non-steroidal anti-inflammatory drug ketoprofen (KTP) was administered as the racemate to cats intravenously (IV) and orally at clinically recommended dose rates of 2 and 1 mg/kg, respectively, to establish its chiral pharmacokinetic and pharmacodynamic properties. After IV dosing, clearance was more than five times greater and elimination half-life and mean residence time were approximately three times shorter for R(-) KTP than for S(+) KTP. Absorption of both S(+) and R(-) enantiomers was rapid after oral dosing and enantioselective pharmacokinetics was demonstrated by the predominance of S(+) KTP, as indicated by plasma AUC of 20.25 (S(+)KTP) and 4.09 (R(-)KTP) microg h/mL after IV and 6.36 (S(+)KTP) and 1.83 (R(-)KTP) microg h/mL after oral dosing. Bioavailability after oral dosing was virtually complete. Reduction in ex vivo serum thromboxane (TX)B(2) concentrations indicated marked inhibition of platelet cyclo-oxygenase (COX)-1 for 24 h after both oral and IV dosing and inhibition was statistically significant for 72 h after IV dosing. Both oral and IV rac-KTP failed to affect wheal volume produced by intradermal injection of the mild irritant carrageenan but wheal skin temperature was significantly inhibited by IV rac-KTP at some recording times. Possible reasons for the disparity between marked COX-1 inhibition and the limited effect on the cardinal signs of inflammation are considered. In a second experiment, the separate enantiomers of KTP were administered IV, each at the dose rate of 1mg/kg. S(+)KTP again predominated in plasma and there was unidirectional chiral inversion of R(-) to S(+)KTP. Administration of both enantiomers again produced marked and prolonged inhibition of platelet COX-1 and, in the case of R(-)KTP, this was probably attributable to S(+)KTP formed by chiral inversion.

Enantiospecific pharmacokinetics of ketoprofen in plasma and synovial fluid of horses with acute synovitis

Pharmacokinetic parameters were established for enantiomers of the nonsteroidal anti-inflammatory drug (NSAID) ketoprofen (KTP) administered as the racemic mixture at a dose of 2.2 mg/kg and as separate enantiomers, each at a dose of 1.1 mg/kg to a group of six horses (five mares and one gelding). A four-period cross-over study in a LPS-induced model of acute synovitis was used. After administration of the racemic mixture S(+)KTP was the predominant enantiomer in plasma as well as in synovial fluid. Unidirectional inversion of R(-) to S(+)KTP was demonstrated but the inversion was less marked than previously reported. It is suggested that this reduction could be because of the influence of the inflammatory reaction on hepatic metabolism. The disposition of KTP enantiomers after administration of the racemic mixture was similar to those observed after administration of S(+) and R(-)KTP. The S(+) and R(-)KTP concentrations in synovial fluid were low and short lasting. After administration of R(-)KTP significant concentrations of the optical antipode were detected in synovial fluid.