Quantitation of meloxicam in the plasma of koalas (Phascolarctos cinereus) by improved high performance liquid chromatography

Preliminary analyses of tryptophan, kynurenine, and the kynurenine: Tryptophan ratio in plasma, as potential biomarkers for systemic chlamydial infections in koalas

Chlamydiosis is the major infectious disease responsible for significant morbidity and mortality in free-living koalas. Recently, it was reported that 28.5% of koalas infected with chlamydiosis were presented with no overt clinical signs. Identification and quantification of changes in plasma biomarkers' fluctuations have the potential to enhance C. pecorum detection and facilitate the monitoring of therapeutic efficacy of antibiotics to treat this disease in koalas. Therefore, concentrations of the essential amino acid tryptophan, tryptophan's metabolite kynurenine, and the kynurenine:tryptophan ratio were quantified by high-performance liquid chromatography in the plasma of clinically normal koalas (n = 35), koalas identified with chlamydial disease (n = 35) and koalas that had other non-chlamydial co-morbidities (n = 10). Results showed that there was a significant difference between the clinically normal versus diseased, and clinically normal versus 'other' (both p < 0.001) in kynurenine plasma concentrations and kynurenine:tryptophan ratio; and also between the clinically normal and diseased in tryptophan plasma concentrations (p = 0.001). Proposed reference ranges of tryptophan, kynurenine, and kynurenine:tryptophan ratio in koalas are: 4.27-10.4 μg/mL, 0.34-1.23 μg/mL, and 0.05-0.22, respectively. Proposed optimal cut-off points to differentiate between clinically normal and diseased are: ≤ 4.75 μg/mL (tryptophan), ≥ 0.88 μg/mL (kynurenine), and ≥ 0.12 (kynurenine:tryptophan); and ≤ 7.67 μg/mL (tryptophan), ≥ 1.18 μg/mL (kynurenine), and ≥ 0.16 (kynurenine:tryptophan) to differentiate between released/recovered and euthanised of the diseased/'other' koalas. Significant differences in haematological and biochemical analytes were in the plasma globulins between the clinically normal and diseased koalas (p = 0.01), and in alkaline phosphatase between the clinically normal and 'other' koalas (p = 0.03). Although these potential biomarkers, especially tryptophan, may not be specific for detecting C. pecorum from the rest of the population, kynurenine and the kynurenine:tryptophan ratio may have a role in identifying unhealthy koalas from the clinically normal ones, irrespective of the underlying cause.

Residue depletion profiles and withdrawal interval estimations of meloxicam in eggs and ovarian follicles following intravenous (Meloxicam solution for injection) and oral (Meloxidyl®) administration in domestic chickens (Gallus domesticus)

Meloxicam is a non-steroidal anti-inflammatory drug (NSAID) commonly prescribed in an extralabel manner for treating chickens in urbanized settings. The objectives of this study were to determine meloxicam depletion profiles in eggs and ovarian follicles and to estimate associated withdrawal intervals (WDI) in laying hens following a single intravenous or repeated oral administration. The observed peak concentration of meloxicam in ovarian follicles were consistently higher than in egg yolk and egg white samples. Terminal half-lives were 31-h, 113-h and 12-h in ovarian follicles, egg yolk and egg white samples, respectively, for repeated oral administrations at 1 mg/kg for 20 doses at 12-h intervals. The terminal half-life following a single intravenous administration at 1 mg/kg was 50-h for ovarian follicles. Meloxicam WDI estimations using ovarian follicle and egg yolk concentration data following 20 doses at 12-h intervals were 36 and 12 days, respectively. Meloxicam WDI estimation using egg yolk concentration data following 8 doses at 24-h intervals was 12 days. These results improve our understanding on the residue depletion of meloxicam from chickens' reproductive tracts and egg products and provide WDIs to help ensure food safety for humans consuming eggs from treated laying hens.

Pharmacokinetic Profile of Doxycycline in Koala Plasma after Weekly Subcutaneous Injections for the Treatment of Chlamydiosis

Simple Summary

Doxycycline is an antimicrobial used for treating chlamydial infections in various species, including the koala. The dose and route of administration used initially are based on first principles. Therefore, this study investigates the absorption, distribution, metabolism, and excretion of subcutaneous doxycycline injections, and evaluates the suitability of the current dosage regimen for inhibiting chlamydial pathogens. The results suggest that the current doxycycline dosage remained therapeutically effective for up to six days after each dose, with some accumulation over successive doses. All koalas in the study improved clinically and tested negative for chlamydial pathogens post-treatment before being released. This study contributes to determining the optimal dosage of doxycycline to treat chlamydiosis safely and effectively in infected koalas.

Abstract

Six mature, male koalas (Phascolarctos cinereus), with clinical signs of chlamydiosis, were administered doxycycline as a 5 mg/kg subcutaneous injection, once a week for four weeks. Blood was collected at standardised time points (T = 0 to 672 h) to quantify the plasma doxycycline concentrations through high-pressure liquid chromatography (HPLC). In five koalas, the doxycycline plasma concentration over the first 48 h appeared to have two distinct elimination gradients; therefore, a two-compartmental analysis was undertaken to describe the pharmacokinetic (PK) profile. The average ± SD maximum plasma concentration (C_max) was 312.30 ± 107.74 ng/mL, while the average time ± SD taken to reach the maximum plasma concentration (T_max) was 1.68 ± 1.49 h. The mean ± SD half-life of the distribution phase (T_1/2 α) and the elimination phase (T_1/2 β) were 10.51 ± 7.15 h and 82.93 ± 37.76 h, respectively. The average ± SD percentage of doxycycline binding to koala plasma protein was 83.65 ± 4.03% at three different concentrations, with a mean unbound fraction (fu) of 0.16. Using probability of target attainment modelling, doxycycline plasma concentrations were likely to inhibit 90% of pathogens with the doxycycline minimum inhibitory concentration (MIC) of 8.0–31.0 ng/mL, and the reported doxycycline MIC to inhibit Chlamydia pecorum isolates at the area under the curve/minimum inhibitory concentration (AUC/MIC) target of ≥24. All koalas were confirmed to be negative for Chlamydia pecorum using loop-mediated isothermal amplification (LAMP), from ocular and penile urethra swabs, three weeks after the last doxycycline injection.

Pharmacokinetics and bioavailability of meloxicam in rainbow trout (Oncorhynchus mykiss) broodstock following intravascular, intramuscular, and oral administrations

The pharmacokinetics and bioavailability of meloxicam were investigated after single intravascular (IV), intramuscular (IM), and oral dose of 1 mg/kg in rainbow trout broodstock at 11 ± 1.2°C. A total of 36 healthy rainbow trout (Oncorhynchus mykiss) broodstock weighing 1.40 ± 0.26 kg was used for the investigation. Plasma concentrations of meloxicam were measured with high-performance liquid chromatography-ultraviolet detection, and pharmacokinetic parameters were calculated by non-compartmental analysis. The elimination half-life for IV, IM, and oral routes was 3.63, 4.55, and 2.95 h, respectively. The IV route for meloxicam showed the total clearance of 0.05 L/h/kg and volume of distribution at a steady state of 0.20 L/kg. The peak plasma concentration was 2.97 μg/ml for the IM route and 0.84 μg/ml for the oral route. The bioavailability was 78.45% for the IM route and 21.48% for the oral route. Meloxicam following IM and oral administration displayed short t_1/2ʎz . The short t_1/2ʎz could be an advantage for the short-term use in acute conditions. The IM route with the good bioavailability can be preferred for the treatment of various conditions. However, developing new oral formulations with the good bioavailability for meloxicam is necessary to minimize stress and trauma through minimal handling in rainbow trout broodstock.

Pharmacokinetic Parameters and Tissue Withdrawal Intervals for Sheep Administered Multiple Oral Doses of Meloxicam

Simple Summary

Meloxicam is an anti-inflammatory drug used to treat pain and inflammation in ruminants including sheep, and pharmacokinetic studies are needed to protect the food supply from drug residues after use in food-producing animals. This study estimated plasma pharmacokinetic parameters and meat withdrawal intervals (WDI) for market sheep after multiple daily oral doses of meloxicam. Single and multiple dose plasma pharmacokinetic studies, a multi-dose tissue depletion study, and a follow-up study to investigate if events prior to slaughter were associated with differences in plasma meloxicam concentrations, all using sample data collected after completion of dosing, were completed. Using regulatory agency methods for calculating withdrawal times, an estimated WDI of at least 10 d following the last dose is recommended for market lambs treated with ten daily oral 1 mg/kg doses of meloxicam tablets suspended in water. The effect of events surrounding slaughter on plasma meloxicam concentrations in lambs is unknown but should be considered if plasma samples are obtained immediately prior to or during the slaughter process and used for pharmacokinetic investigations.

Abstract

Meloxicam is an anti-inflammatory drug used to treat pain and inflammation in ruminants including sheep, and pharmacokinetic studies are needed to protect the food supply from drug residues after use in food-producing animals. This study estimated plasma pharmacokinetic parameters and meat withdrawal intervals (WDI) for market sheep after multiple daily oral doses of meloxicam. Single and multiple dose plasma pharmacokinetic studies, a multi-dose tissue depletion study, and a follow-up study to investigate if events prior to slaughter were associated with differences in plasma meloxicam concentrations, all using sample data collected after completion of dosing, were completed. Using regulatory agency methods for calculating withdrawal times, an estimated WDI of at least 10 d following the last dose is recommended for market lambs treated with 10 daily oral 1 mg/kg doses of meloxicam tablets suspended in water. The effect of events surrounding slaughter on plasma meloxicam concentrations in lambs is unknown but should be considered if plasma samples are obtained immediately prior to or during the slaughter process and used for pharmacokinetic investigations.

Preliminary Investigation into a Novel Sustained-Release Formulation of Meloxicam in Sheep (Ovis aries)-Pharmacokinetic Profile

Simple Summary

Meloxicam is an effective non-steroidal anti-inflammatory drug (NSAID) suitable for ameliorating pain in sheep. Pain caused by husbandry procedures and other inflammatory conditions in sheep can persist for an extended time beyond the duration of action of currently available formulations of NSAIDs. This study investigates a novel sustained-release formulation of meloxicam to determine its potential for extended pain alleviation. Compared to a conventional formulation of meloxicam, the sustained-release formulation provided extended half-life making it a suitable candidate for providing extended pain relief.

Abstract

This study is a preliminary investigation describing the pharmacokinetic profile of a novel subcutaneous sustained-release meloxicam formulation (SRMF) in sheep. Six merino ewe hoggets (41.5 ± 4.6 kg) were treated with a novel subcutaneous SRMF at 2 mg/kg bodyweight (BW). Blood samples were collected at t = 0, 2, 4, 6, 8, 10, 12, 24, 48, 96, 144, 168, 192, and 336 h following treatment, and interstitial (ISF) fluid samples were collected at periods of 8 to 12 h, 12 to 24 h, 24 to 48 h, 48 to 52 h, and 92 to 96 h following treatment. High-pressure liquid chromatography (HPLC) analysis with ultraviolet detection was utilised to determine the concentration of meloxicam in plasma and ISF. The SRMF exhibited the following mean (±SD) pharmacokinetic indices: C_max of 1.58 μg/mL (±0.82 μg/mL) at a T_max of 10.0 h (±1.79 h), and half life (t_1/2) of 31.4 h (±13.17 h) in sheep plasma. Interstitial fluid samples were collected from three of the six sheep, with a decrease in meloxicam concentration exhibited over 52 h. This study demonstrates a variable extended t_1/2, a delayed T_max, and a lower C_max of the SRMF, as compared to that of a conventional meloxicam formulation (CMF) in sheep, as previously referenced (t_1/2: 14.28 h; T_max: 5 h; C_max: 15.94 μg/mL). Further research to determine the clinical efficacy and safety of the SRMF in sheep is warranted.

Ultrasensitive and simultaneous detection of 6 nonsteroidal anti-inflammatory drugs by colloidal gold strip sensor

In this work, an oxicam group-selective monoclonal antibody against 6 nonsteroidal anti-inflammatory drugs (NSAID; meloxicam, lornoxicam, piroxicam, sudoxicam, droxicam, and tenoxicam) was prepared. Also, a spacer arm with carboxyl group was derived at the hydroxyl of meloxicam to generate the meloxicam hapten. The half-maximal inhibitory concentrations (IC₅₀) were, respectively, 0.31 ng/mL for meloxicam, 0.49 ng/mL for lornoxicam, 2.90 ng/mL for piroxicam, 1.95 ng/mL for sudoxicam, 3.08 ng/mL for droxicam, and 5.36 ng/mL for tenoxicam. A colloidal gold immunochromatographic strip based on the monoclonal antibody was developed for the detection of these 6 NSAID in milk. The results could be obtained by the naked eye in 10 min, and the cut-off values and the visual limits of detection in real samples were 5, 5, 10, 10, 25, and 25 ng/mL, and 0.25, 1, 0.5, 0.5, 1, and 1 ng/mL, respectively. This immunochromatopgraphic strip is a suitable tool for on-site detection and screening of oxicam NSAID in milk samples.

The Application of TLC and Densitometry for Quantitative Determination of Meloxicam in Tablets

Background:

Meloxicam is as a non-steroidal anti-inflammatory drug that indicates a strong anti-inflammatory, analgesic and antipyretic activity. It is used in the treatment of osteoarthritis arthritis, osteoarthritis and rheumatoid arthritis in the form of various pharmaceutical preparations.

Objective:

The aim of the work was an elaboration of chromatographic conditions enabling the complete separation of impurities A and B from meloxicam and also its quantitative determination in tablets with use of TLC combined with densitometry as well as the comparison of the method proposed with that described in the literature by Starek and Krzek.

Methods:

The mixture of ethyl acetate: toluene: n-butylamine (2:2:1, v/v/v) was used as a mobile phase. Determination of meloxicam was performed on silica gel and aluminium oxide plates. Chromatographic conditions presented in this work are better than those described by Starek and Krzek.

Results:

Linearity of the method for both types of plates was in the range from 1.0 to 5.0 µg/spot. Limit of quantification for silica gel plates was 0.18 µg/spot, while for aluminium oxide plates it was 0.26 µg/spot. Limit of detection has been also specified, 0.06 μg/spot for silica gel plates and 0.08 μg/spot for aluminium oxide plates. The average amount of meloxicam in tablets obtained on silica gel plates was 100.4%, and on the aluminium oxide plates it was 100.3%.

Conclusion:

The developed method of determination of meloxicam using thin layer chromatography combined with densitometry turned out to be accurate, precise and specific. It can be successfully applied in quality control of meloxicam.

In vitro binding of cefovecin to plasma proteins in Australian marsupials and plasma concentrations of cefovecin following single subcutaneous administration to koalas (Phascolarctos cinereus)

BACKGROUND

Cefovecin has a long duration of antibiotic activity in cats and dogs, somewhat attributable to its high plasma protein binding.

AIMS

To determine the cefovecin binding to plasma proteins in vitro in selected Australian marsupials and to quantify the change in cetovecin concentration over time following subcutaneous injection in koalas.

METHODS AND RESULTS

Various cefovecin concentrations were incubated with plasma and quantified using HPLC. The median (range) bound percentages when 10 μg/mL of cefovecin was incubated with plasma were 11.1 (4.1-20.4) in the plasma of the Tasmanian devil, 12.7 (5.8-17.3) in the koala, 18.9 (14.6-38.0) in the eastern grey kangaroo, 16.9 (15.7-30.2) in the common brush-tailed possum, 37.6 (25.3-42.3) in the eastern ring-tailed possum and 36.4 (35.0-38.3) in the red kangaroo, suggesting that cefovecin may have a shorter duration of action in these species than in cats and dogs. Cefovecin binding to plasma proteins in thawed, frozen equine plasma was also undertaken for assay quality control and the median (range) plasma protein binding (at 10 μg/mL) was 95.6% (94.9-96.6%). Cefovecin was also administered to six koalas at 8 mg/kg subcutaneously and serial blood samples were collected at 3, 6, 24, 48, 72, 96 h thereafter. Cefovecin plasma concentrations were not quantifiable in four koalas and in the other two, the mean plasma concentration at t = 3 h was 1.04 ± 0.01 μg/mL.

CONCLUSION

Because of the limited pharmacokinetic data generated, no further pharmacokinetic analysis was performed; however, a single injected bolus of cefovecin is likely to have a short duration of action in koalas (hours, rather than days).

With or Without Internal Standard in HPLC Bioanalysis. A Case Study

The mandatory strategy of using internal standard in HPLC is still controversial. Despite that the introduction of internal standard methodology in the early stage of development of HPLC technology was used to improve method accuracy and precision, there are still practical situations in which a simple external standard quantification is adequate. The aim of the study is to compare the determination of meloxicam (MXC) in human plasma by HPLC with or without using an internal standard according to some key points related to the reason of introducing the internal standardization such as the reducing of sample preparation errors or variability for low injection volumes. The HPLC analysis was performed on reversed phase with UV detection after protein precipitation. Piroxicam (PXC) was used as an internal standard. The two methods are compared in terms of accuracy and precision over the same concentration range. The stability of the analyte has been proved. According to the results, the quantitative determination of MXC in human plasma after simple protein precipitation by using PXC as an internal standard does not bring any significant improvement of accuracy and precision of the experimental measurements.

Percentage of faecal excretion of meloxicam in the Cape vultures (Gyps corprotheres)

Asian Gyps vulture species are gradually recovering from the devastating effect of diclofenac being present in contaminated carcasses. This drug was responsible for the death of over 10 million vultures in India, Nepal and Pakistan. To prevent the extinction of vultures, meloxicam was introduced after the ban of veterinary diclofenac. Meloxicam's safety in vultures was attributed to its short elimination half-life in contrast with diclofenac. The reason for the rapid elimination of meloxicam is yet to be explained. The aim of this study was to evaluate the role of biotransformation in the elimination of meloxicam. Six Cape griffon vultures (Gyps coprotheres) were treated with 2 mg/kg meloxicam intramuscularly for faecal and plasma quantification of meloxicam concentration over time. In the plasma meloxicam was characterised by a half-life, mean residence time, clearance and volume of distribution at steady state of 0.37 ± 0.10 h, 0.90 ± 0.12 h, 0.02 ± 0.00 l/h kg and 0.02 ± 0.00 l/kg respectively (presented as geometric mean). Over the 24 h monitoring period, the total non-metabolised meloxicam in the faeces was 1.35 ± 0.71% of the total concentration in the plasma. Based on the short meloxicam elimination half-life and low cumulative concentration of total faecal meloxicam over a period in excess of 10 half-lives, this study indicates that Cape griffon vultures are efficient metaboliser of meloxicam, which is suggestive of different set of cytochrome enzymes being involved in the metabolism to that for diclofenac in this species. Identification of orthologous human CYP2C9 and CYP3A4 enzyme families in vultures will be an important further step in explaining the differences in the metabolic pathway(s) of meloxicam and diclofenac for the species.

In vitro hepatic microsomal metabolism of meloxicam in koalas (Phascolarctos cinereus), brushtail possums (Trichosurus vulpecula), ringtail possums (Pseudocheirus peregrinus), rats (Rattus norvegicus) and dogs (Canis lupus familiaris)

Quantitative and qualitative aspects of in vitro metabolism of the non-steroidal anti-inflammatory drug meloxicam, mediated via hepatic microsomes of specialized foliage (Eucalyptus) eating marsupials (koalas and ringtail possums), a generalized foliage eating marsupial (brushtail possum), rats, and dogs, are described. Using a substrate depletion method, intrinsic hepatic clearance (in vitro Clint) was determined. Significantly, rates of oxidative transformation of meloxicam, likely mediated via cytochromes P450 (CYP), were higher in marsupials compared to rats or dogs. The rank order of apparent in vitro Clint was brushtail possums (n=3) (mean: 394μL/min/mg protein), >koalas (n=6) (50), >ringtail possums (n=2) (36) (with no significant difference between koalas and ringtail possums), >pooled rats (3.2)>pooled dogs (in which the rate of depletion, as calculated by the ratio of the substrate remaining was <20% and too slow to determine). During the depletion of meloxicam, at a first-order rate constant, 5-hydroxymethyl metabolite (M1) was identified in the brushtail possums and the rat as the major metabolite. However, multiple hydroxyl metabolites were observed in the koala (M1, M2, and M3) and the ringtail possum (M1 and M3) indicating that these specialized foliage-eating marsupials have diverse oxidation capacity to metabolize meloxicam. Using a well-stirred model, the apparent in vitro Clint of meloxicam for koalas and the rat was further scaled to compare with published in vivo Cl. The closest in vivo Cl prediction from in vitro data of koalas was demonstrated with scaled hepatic Cl(total) (average fold error=1.9) excluding unbound fractions in the blood and microsome values; whereas for rats, the in-vitro scaled hepatic Cl fu(blood, mic), corrected with unbound fractions in the blood and microsome values, provided the best prediction (fold error=1.86). This study indicates that eutherians such as rats or dogs serve as inadequate models for dosage extrapolation of this drug to marsupials due to differences in hepatic turnover rate. Furthermore, as in vivo Cl is one of the pharmacokinetic indexes for determining therapeutic drug dosages, this study demonstrates the utility of in vitro to in vivo scaling as an alternative prediction method of drug Cl in koalas.