Influence of oxytetracycline on carprofen pharmacodynamics and pharmacokinetics in calves

Moxidectin is a candidate for use as an in vivo internal standard in pharmacokinetic studies, as demonstrated with use in simultaneous tissue cage and ultrafiltration fluid collection

In vivo ultrafiltration has been used in veterinary pharmacokinetics since the early 2000's as an improvement on the tissue cage model which enables sampling of fluids from extra-circulatory compartments. Variability in analyte recovery from ultrafiltration samples, due to membrane fouling or tissue inflammation, has been a concern for this technique. Internal standards may be used to scale or verify the unknown result, such as is common in analytical extractions and in vivo microdialysis. Eight merino sheep were implanted with subcutaneous tissue cages and 2 weeks prior to the initiation of the study the sheep were injected with 0.2 mg/kg moxidectin subcutaneously. On the day of the study ultrafiltration probes were inserted subcutaneously. At time zero 4 mg/kg of carprofen was injected intravenously. Plasma, tissue cage, and ultrafiltration samples were taken 30 min before and 0.5, 1, 2, 3, 4, 5, 7, 24, 36, 48, 72 h after dosing. Carprofen and moxidectin concentrations were measured by LC-MS/MS. Pharmacokinetic parameters were estimated using Monolix for both the carprofen concentrations and the moxidectin corrected carprofen concentrations. The ultrafiltration probes failed to consistently produce enough sample volume to analyse. Moxidectin concentrations in the plasma and tissue cage fluid were stable throughout the 72 h sampling window. Moxidectin proved to be suitable as an in vivo internal standard for pharmacokinetic research using, tissue cages, plasma sampling and ultrafiltration probes, but the application of ultrafiltration techniques requires refinement.

Swine as the Animal Model for Testing New Formulations of Anti-Inflammatory Drugs: Carprofen Pharmacokinetics and Bioavailability of the Intramuscular Route

Carprofen (CP) is a non-steroidal anti-inflammatory drug (NSAID) frequently used to treat respiratory diseases in numerous small animals, but also in large species. CP is a formidable candidate for further therapeutic research of human inflammatory diseases using the pig as an animal model. However, CP administration in swine is very uncommon and respective pharmacokinetics/bioavailability studies are scarce. A simultaneous population pharmacokinetic analysis after CP intravenous and intramuscular administrations in pigs has shown high extent and rate of absorption and a similar distribution profile with respect to man and other mammals. However, clearance and half-life values found in swine suggest a slower elimination process than that observed in man and some other animal species. Although not reported in other species, liver and kidney concentrations achieved at 48 h post-intramuscular administration in pigs were ten times lower than those found in plasma. Simulations pointed to 4 mg/kg every 24 h as the best dosage regimen to achieve similar therapeutic levels to those observed in other animal species. All these findings support the use of pig as an animal model to study the anti-inflammatory effects of CP in humans.

The use of toxicokinetics and exposure studies to show that carprofen in cattle tissue could lead to secondary toxicity and death in wild vultures

Veterinary medicines can be extremely damaging to the environment, as seen with the catastrophic declines in Gyps vulture in South Asia due to their secondary exposure to diclofenac in their primary food source. Not surprisingly, concern has been raised over other similar drugs. In this study, we evaluate the toxicity of carprofen to the Gyps vulture clade through plasma pharmacokinetics evaluations in Bos taurus cattle (their food source) and Gyps africanus (a validated model species); tissue residues in cattle; and the effect of carprofen as a secondary toxicant as both tissue-bound residue or pure drug at levels expected in cattle tissues. Carprofen residues were highest in cattle kidney (7.72 ± 2.38 mg/kg) and injection site muscle (289.05 ± 98.96 mg/kg of dimension of 5 × 5 × 5 cm). Vultures exposed to carprofen as residues in the kidney tissue or pure drug equivalents showed no toxic signs. When exposed to average injection site concentrations (64 mg/kg) one of two birds died with evidence of severe renal and liver damage. Toxicokinetic analysis revealed a prolonged drug half-life of 37.75 h in the dead bird as opposed to 13.99 ± 5.61 h from healthy birds dosed intravenously at 5 mg/kg. While carprofen may generally be harmless to Gyps vultures, its high levels at the injection site in treated cattle can result in lethal exposure in foraging vultures, due to relative small area of tissue it is found therein. We thus suggest that carprofen not be used in domesticated ungulates in areas where carcasses are accessible or provided to vultures at supplementary feeding sites.

Evaluation of Bioequivalence of Two Long-Acting 20% Oxytetracycline Formulations in Pigs

The aim of this study was to explore the bioequivalence of long-acting oxytetracycline in two formulations, a reference formulation (Terramycin 20% LA, Pfizer) and a test one (Kangtekang 20% LA, Huishen). Both formulations were administered intramuscularly at 20 mg/kg body weight at each of 24 healthy animals during a two-period crossover parallel experimental design. The oxytetracycline (OTC) concentrations in plasma were measured by high-performance liquid chromatography, and the limit of quantification was 0.05 µg/ml with a recovery ratio of above 90%. Moreover, the descriptive pharmacokinetics parameters (Cmax, AUC0-144h, and AUC0-∞) were calculated and compared under analysis of variance, and 90% confidence interval (CI) were compared, except for Tmax analyzed by non-parametric tests based on Wilcoxons's signed rank test. The comparison results of Cmax, AUC0-144h, AUC0-∞, and Tmax were 5.066 ± 0.486, 5.071 ± 0.877 µg/ml, 118.926 ± 13.259, 126.179 ± 17.390 µg h/ml, 123.087 ± 13.906, 130.732 ± 18.562 µg h/ml, 0.740 ± 0.278, 0.650 ± 0.258 h, respectively, and did not reveal any significant differences. In addition, 90% CIs of these ratios for reference and test product were within an interval of 80-125%, and the relative bioavailability of test one was (94.291 ± 15.287)%. Therefore, it has been concluded that test OTC was bioequivalent to the reference formulation in pigs.

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

The effect of flunixin transdermal pour-on solution (Finadyne® Transdermal; MSD Animal Health) on prostaglandin E₂ (PGE₂) synthesis in bovine inflammatory exudate was evaluated in a tissue cage model of acute inflammation. Twelve calves were randomly allocated to two-treatment groups over two sequences. Three weeks prior to the first period, sterile hollow perforated polyethylene balls were surgically embedded in the subcutis at four distinct sites in each animal. On the first day of each period, an aseptic inflammation was induced by injecting 0.5mL of a 2% carrageenan solution into the lumen of each tissue cage. Treatment with either flunixin transdermal or negative control (NaCl) immediately followed. 0.5mL of exudate was collected prior to challenge, and at 2, 4, 8, 12, 24, 36 and 48h after challenge. Exudate PGE₂ concentrations were analyzed using ultra-high pressure liquid chromatography coupled with tandem mass spectrometry method. Mean PGE₂ concentrations were consistently lower in calves treated with flunixin transdermal than those measured in calves treated with negative control, indicating an inhibitory activity on cyclooxygenase. Inhibition was the highest at 8h after treatment, and differences with the negative control were significant at +8, 24, 36 and 48h. The flunixin transdermal formulation was effective in reducing PGE₂ concentrations in bovine exudate following an induced inflammation. Its anti-inflammatory action started in the first hours after treatment and lasted up to 48h.

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.

Antimicrobial synergy between carprofen and doxycycline against methicillin-resistant Staphylococcus pseudintermedius ST71

Background

New therapeutic strategies are needed to face the rapid spread of multidrug-resistant staphylococci in veterinary medicine. The objective of this study was to identify synergies between antimicrobial and non-antimicrobial drugs commonly used in companion animals as a possible strategy to restore antimicrobial susceptibility in methicillin-resistant Staphylococcus pseudintermedius (MRSP).

Results

A total of 216 antimicrobial/non-antimicrobial drug combinations were screened by disk diffusion using a clinical MRSP sequence type (ST) 71 strain resistant to all six antimicrobials tested (ampicillin, ciprofloxacin, clindamycin, doxycycline, oxacillin and trimethoprim/sulfamethoxazole). The most promising drug combination (doxycycline-carprofen) was further assessed by checkerboard testing extended to four additional MRSP strains belonging to ST71 or ST68, and by growth inhibition experiments.

Seven non-antimicrobial drugs (bromhexine, acepromazine, amitriptyline, clomipramine, carprofen, fluoxetine and ketoconazole) displayed minimum inhibitory concentrations (MICs) ranging between 32 and >4096 mg/L, and enhanced antimicrobial activity of one or more antimicrobials. Secondary screening by checkerboard assay revealed a synergistic antimicrobial effect between carprofen and doxycycline, with the sum of the fractional inhibitory concentration indexes (ΣFICI) ranging between 0.3 and 0.5 depending on drug concentration. Checkerboard testing of multiple MRSP strains revealed a clear association between synergy and carriage of tetK, which is a typical feature of MRSP ST71. An increased growth inhibition was observed when MRSP ST71 cells in exponential phase were exposed to 0.5/32 mg/L of doxycycline/carprofen compared to individual drug exposure.

Conclusions

Carprofen restores in vitro susceptibility to doxycycline in S. pseudintermedius strains carrying tetK such as MRSP ST71. Further research is warranted to elucidate the molecular mechanism behind the identified synergy and its linkage to tetK.

Repurposing drugs for treatment of tuberculosis: a role for non-steroidal anti-inflammatory drugs

INTRODUCTION

The number of cases of drug-resistant Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), has risen rapidly in recent years. This has led to the resurgence in repurposing existing drugs, such as non-steroidal anti-inflammatory drugs (NSAIDs), for anti-TB treatment.

SOURCES OF DATA

Evidence from novel drug screening in vitro, in vivo, pharmacokinetic/pharmacodynamics analyses and clinical trials has been used for the preparation of this systematic review of the potential of NSAIDs for use as an adjunct in new TB chemotherapies.

AREAS OF AGREEMENT

Certain NSAIDs have demonstrated inhibitory properties towards actively replicating, dormant and drug-resistant clinical isolates of M. tuberculosis cells.

AREAS OF CONTROVERSY

NSAIDs are a diverse class of drugs, which have reported off-target activities, and their endogenous antimicrobial mechanism(s) of action is still unclear.

GROWING POINTS

It is essential that clinical trials of NSAIDs continue, in order to assess their suitability for addition to the current TB treatment regimen. Repurposing molecules such as NSAIDs is a vital, low-risk strategy to combat the trend of rapidly increasing antibiotic resistance.