Pharmacokinetics of marbofloxacin in freshwater crocodiles (Crocodylus siamensis) after intravenous and intramuscular administration

Pharmacokinetics of tildipirosin in estuarine (Crocodylus porosus) and freshwater (Crocodylus siamensis) crocodiles

Tildipirosin is a macrolide antimicrobial. It is authorised for the treatment and prevention of respiratory disease in cattle and pigs. There are no data on its administration in crocodiles. Therefore, this study evaluated the disposition kinetics of tildipirosin after intravenous (dose: 2 mg/kg) and intramuscular (doses: 2 and 4 mg/kg) administration in two crocodilian species (estuarine and freshwater; n = 5). Tildipirosin plasma concentrations were quantified by a validated HPLC method. Plasma concentrations obtained at each extraction time were analysed by non-compartmental methods. In the estuarine and freshwater crocodiles, the apparent volumes of distribution of tildipirosin after intravenous administration were 0.36 ± 0.10 and 1.48 ± 0.26 L/kg, respectively. These values, suggesting poorer tissue distribution, were much lower than those obtained in mammals. There was complete bioavailability of tildipirosin after intramuscular route at a dose of 2 mg/kg; however, at a dose of 4 mg/kg the bioavailability decreased by about 20-25 %. Furthermore, the pharmacokinetics of tildipirosin were markedly different in the two crocodilian species. Considering a MIC of 0.5 µg/mL, the surrogate marker AUC0-24/MIC indicates that tildipirosin would greatly exceed the value of 65 h for both crocodile species and dose levels tested. This suggests that both doses (2 and 4 mg/kg) may provide a bactericidal effect. Therefore, based on the absence of adverse reactions following the administration of tildipirosin in both crocodilian species, and considering its favourable pharmacokinetic properties, tildipirosin may be useful in treating infections in these reptiles.

Pharmacokinetics and pharmacodynamics of dextroketamine alone or combined with midazolam in Caiman crocodilus

Pharmacokinetics studies of anesthetic agents are important for understanding of the pharmacology and metabolism of anesthetic agents in reptilians. This study was designed to examine the pharmacokinetic and pharmacodynamic properties of intravenous dextroketamine alone or combined with midazolam in Caiman crocodilus. Eight caimans were anesthetized with dextroketamine (10 mg/kg; group D) or dextroketamine and midazolam (10 and 0.5 mg/kg respectively; group DM) into the occipital venous sinus. The pharmacokinetic parameters were calculated by HPLC using a non-compartmental modeling. Serial blood samples were collected at baseline and within 15 and 30 min, and 11.5, 2, 4, 8, 12, 24 and 48 h of drug administration. Sedation status over time differed between groups. All animals in group D (8/8; 100%) showed signs of light sedation at t10. Half (4/8; 50%) of these caimans did not progress to deeper levels of sedation. In spite of light sedation at t10, animals in group DM were deeply sedated within 13.13 ± 7.04 min of anesthetic agent injection. The area under the plasma concentration-time curve (AUC0-48) and half-life of dextroketamine changed significantly after combination with midazolam. Even without significant changes in clearance, the almost two-fold increase in the half-life of dextroketamine suggests a slower rate of elimination.

Pharmacokinetic disposition of marbofloxacin after intramuscular administration in estuarine crocodiles (Crocodylus porosus)

To date, the pharmacokinetics of fluoroquinolones in estuarine crocodiles (Crocodylus porosus) have been reported for enrofloxacin but not for marbofloxacin (MBF), which is a broad-spectrum antibiotic used only in veterinary medicine. This study investigated the pharmacokinetics of MBF after intramuscular administration at two difference dosages (2 and 4 mg/kg body weight) in estuarine crocodiles and estimated pharmacokinetic/pharmacodynamic (PK/PD) surrogate parameters for the optimization of dosage regimens. Ten treated estuarine crocodiles were divided into two groups (n = 5) using a randomization procedure according to a parallel study design. Blood samples were collected at assigned times up to 168 h. MBF plasma samples were cleaned up using liquid-liquid extraction and analyzed using a validated high-performance liquid chromatography method with fluorescence detection. A non-compartment approach was used to fit the plasma concentration of MBF vs time curve for each crocodile. The plasma concentrations of MBF were quantifiable for up to 168 h in both groups. The elimination half-life values of MBF were long (33.99 and 39.28 h for 2 and 4 mg/kg, respectively) with no significant differences between the groups. The average plasma protein binding of MBF was 30.85%. According to the surrogated PK/PD parameter (AUC0-24 -to-MIC ratio >100-125), the 2 and 4 mg/kg dosing rates should be effective for bacteria with MIC values lower than 0.125 μg/mL and 0.35 μg/mL, respectively.

PHARMACOKINETICS OF SINGLE INTRAMUSCULAR ADMINISTRATION OF CEFTIOFUR CRYSTALLINE FREE ACID IN AMERICAN ALLIGATORS (ALLIGATOR MISSISSIPPIENSIS)

A pharmacokinetic study of ceftiofur crystalline free acid sterile oil suspension (CCFA) was performed in six apparently healthy juvenile American alligators (Alligator mississippiensis). A single intramuscular dose of 30 mg/kg was administered in the triceps muscle. Blood samples were collected prior to treatment and at 4, 12, 24, 48, 72, 120, 144, 192, 288, and 366 h post administration. Plasma samples were analyzed for ceftiofur equivalent concentrations using liquid chromatography-mass spectrometry. Pharmacokinetic parameters were determined by noncompartmental analysis. Mean peak plasma concentration was 23.2 µg/ml (range, 16.0-27.9), median time to maximum concentration was 72 h (range, 72-120), mean area under the curve from 0 to 366 h postdose was 4.24 h · mg/ml (range, 3.54-4.97), and mean terminal half-life was 143 h (range, 90.8-220). Plasma concentrations were maintained above the minimum inhibitory concentration for this study of 2.0 µg/ml, which was established from similar CCFA pharmacokinetic studies in other reptilian species, through the end of the data collection of 366 h. Because of prolonged plasma concentrations, a dosing interval could not be established in this study. Future studies should include extended collection time points and multidose studies to determine dosing regimens.

Pharmacokinetic characteristics of azithromycin in freshwater crocodiles (Crocodylus siamensis) after intramuscular administration at three different dosages

The study evaluated the pharmacokinetic features of azithromycin (AZM) in 15 freshwater crocodiles (Crocodylus siamensis) in Thailand. The crocodiles were administered a single intramuscular (i.m.) injection of AZM at three different dosages of 2.5, 5, and 10 mg/kg body weight (b.w.). Blood samples were collected at pre-assigned times up to 168 h. The plasma concentrations of AZM were measured using a validated liquid chromatography-tandem mass spectrometry method. The plasma concentration of AZM were quantifiable for up to 168 h after i.m. administration at the three different dosages. A non-compartmental model was used to fit the plasma concentration of AZM versus the time curve for each crocodile. The elimination half-life values of AZM were 33.70, 38.11, and 34.80 h following i.m. injection after dosages of 2.5, 5, and 10 mg/kg b.w., respectively. There were no significant differences among groups. The results indicated that the overall rate of elimination of AZM in freshwater crocodiles was relatively slow. The maximum concentration and area under the curve from zero to the last values of AZM increased in a dose-dependent fashion. The average binding percentage of AZM to plasma protein was 48.66%. Based on the pharmacokinetic data, the susceptibility break-point and the surrogate PK-PD index (T > MIC), the intramuscular administration of AZM at a dose of 10 mg/kg b.w. might be appropriate for the treatment of susceptible bacterial infections (MIC < 4 μg/ml) in freshwater crocodiles.

Pharmacokinetics of danofloxacin in freshwater crocodiles (Crocodylus siamensis) after intramuscular injection

The present study evaluated the pharmacokinetic profiles of danofloxacin (DNX) in freshwater crocodiles (Crocodylus siamensis), following single intramuscular (i.m.) administrations at two different dosages of 6 and 12 mg/kg body weight (b.w.). Blood samples were collected at assigned times up to 168 h. DNX in the harvested crocodile plasma was extracted using liquid-liquid extraction and analyzed using a validated high-performance liquid chromatography method equipped with fluorescence detection. The pharmacokinetic analysis was performed using a non-compartmental approach. DNX in plasma was quantifiable from 5 min to 168 h after i.m. administration at the two dosages in freshwater crocodiles. The area under the curve (AUC) and maximum concentration (C_max ) values increased in a dose-dependent fashion. Long elimination half-life (48.18 and 67.29 h) and low clearance (0.024 and 0.020 ml/g h) were obtained in the high- and low-dose groups, respectively. According to the pharmacokinetic-pharmacodynamic surrogate (AUC_0-24h /MIC > 125), i.m. single administration of DNX at a dosage of 6 mg/kg b.w. is predicted to have antibacterial success for disease caused by bacteria with MIC < 0.04 μg/ml in the freshwater crocodile, C. siamensis.

Pharmacokinetic profiles of clarithromycin in freshwater crocodiles (Crocodylus siamensis)

Clarithromycin (CLA) is a new β-lactamase-resistant macrolide antibiotic with potent activity against gram-positive and some gram-negative bacteria. To the authors' best knowledge, limited pharmacokinetic information to establish suitable therapeutic plans is available for freshwater crocodiles. To assess the prudent use of antibiotic in reptiles, this study was conducted to explore the pharmacokinetic characteristics of CLA in the freshwater crocodile, Crocodylus siamensis, following either single intravenous (i.v.) or intramuscular (i.m.) administration at a dosage of 2.5 mg/kg body weight (b.w.). Blood samples were collected at assigned times up to 168 h. CLA plasma samples were cleaned up using liquid-liquid extraction, and analysed by a validated liquid chromatography tandem-mass spectrometry (LC-MS/MS). CLA was quantifiable from 5 min to 72 h after i.v. administration, whereas it was detectable for 168 after i.m. administration at an identical dose rate. A non-compartmental model was used to fit the plasma concentration of CLA versus time curve for each crocodile. The t_1/2λz value, similar for both routes (20 h), indicated that the overall rate of elimination of CLA in crocodiles is relatively slow. The average i.m. F% was complete. The protein plasma bound was found to be about 30%. CLA is a time-dependent antibiotic, and the T > MIC is the best PK/PD predictor for its efficacy. The CLA dosage of 2.5 mg/kg appeared to produce an appropriate value of the PK-PD surrogate that predicts antibacterial success for disease caused by susceptible bacteria.

Pharmacokinetics of a Long-Acting Formulation of Oxytetracycline in Freshwater Crocodiles (Crocodylus siamensis) after Intramuscular Administration at Three Different Dosages

Simple Summary

The oxytetracycline long-acting formulation (OTC-LA) is used to treat sensitive pathogenic bacteria in the freshwater crocodile, Crocodylus siamensis. The pharmacokinetic profiles of differential dosages of OTC after intramuscular administration were investigated to determine the appropriate dosage for the treatment of bacterial infections in freshwater crocodiles. In freshwater crocodiles, dosages of 10 and 20 mg/kg produced OTC plasma concentrations higher than 2.0 µg/mL as a minimum inhibitory concentration (MIC) for 192 h and 216 h after intramuscular administration, respectively, while the OTC plasma concentration remained below the MIC of 2.0 µg/mL at a dosage of 5 mg/kg body weight (b.w.). When considering plasma protein binding of 32%, an intramuscular (i.m.) administration at a dosage of 10 mg/kg b.w. might be effective for two weeks to treat sensitive pathogenic bacteria in freshwater crocodiles.

Abstract

To date, the necessary pharmacokinetic information has been limited to establish suitable therapeutic plans for freshwater crocodiles. Therefore, this study was conducted to evaluate the pharmacokinetic profile of the oxytetracycline long-acting formulation (OTC-LA) in the freshwater crocodile, Crocodylus siamensis, following a single intramuscular (i.m.) administration at three different dosages of 5, 10 and 20 mg/kg body weight (b.w.). Blood samples were collected at assigned times up to 216 h after i.m. administration at the three different dosages. The plasma concentrations of OTC were measured using a validated liquid chromatography tandem-mass spectrometry (LC-MS/MS) method. The C_max (± SD) values of OTC were 2.15 ± 0.51 µg/mL, 7.68 ± 1.08 µg/mL and 17.08 ± 2.09 µg/mL at doses of 5, 10 and 20 mg/kg b.w., respectively. The elimination half-life values were 33.59 ± 2.51 h, 38.42 ± 5.47 h and 38.04 ± 1.98 h at dosages of 5, 10 and 20 mg/kg b.w., respectively. Based on the pharmacokinetic data, the pharmacokinetic/pharmacodynamic (PK/PD) index, the susceptibility break-point and plasma protein binding, a dosage once every two weeks of 10 mg/kg b.w. OTC intramuscularly might be suitable for initiating the treatment of susceptible bacterial infections in freshwater crocodiles. However, further PK/PD studies are warranted to confirm whether the dose rates used in this study can produce longer-term antimicrobial success for diseases caused by susceptible bacteria in freshwater crocodiles.

Pharmacokinetic profiles of amoxicillin trihydrate in freshwater crocodiles (Crocodylus siamensis) after intramuscular administration at two doses

The aim of the present study was to elucidate the pharmacokinetic profiles of amoxicillin trihydrate (AMX) in Siamese freshwater crocodiles (Crocodylus siamensis). Crocodiles were administered a single intramuscular injection of AMX, at a dose of either 5 or 10 mg/kg body weight (b.w.). Blood samples were collected at preassigned times up to 120 hr. The plasma concentrations of AMX were measured using a validated liquid chromatography tandem-mass spectrometry method. AMX plasma concentrations were quantifiable for up to 72 hr (5 mg/kg b.w.) and 96 hr (10 mg/kg b.w.). The elimination half-life (t_{1/2λ z} ) of AMX following dosing at 5 mg/kg b.w. (8.72 ± 0.61 hr) was almost identical to that following administration at 10 mg/kg b.w (8.98 ± 1.13 hr). The maximum concentration and area under the curve from zero to the last values of AMX increased in a dose-dependent fashion. The average binding percentage of AMX to plasma protein was 21.24%. Based on the pharmacokinetic data, susceptibility break point, and the surrogate PK-PD index (T > MIC, 0.25 μg/ml), intramuscular administration of AMX at dose of 5 mg/kg b.w. every 4 days might be appropriate for the treatment of susceptible bacterial infections in freshwater crocodiles.

Pharmacokinetics of marbofloxacin in Green sea turtles (Chelonia mydas) following intravenous and intramuscular administration at two dosage rates

Limited pharmacokinetic information to establish suitable therapeutic plans is available for green sea turtles. Therefore, the present study was conducted to evaluate the pharmacokinetic characteristics of marbofloxacin (MBF) in the green sea turtle, Chelonia mydas, following single intravenous (i.v.) or intramuscular (i.m.) administration at two dosages of 2 and 4 mg/kg body weight (b.w.). Blood samples were collected at assigned times up to 168 hr. MBF in plasma was extracted using liquid-liquid extraction and analyzed by a validated high-performance liquid chromatography (HPLC). MBF was quantifiable from 15 min to 96 hr after i.v. and i.m. administrations at two dose rates. A noncompartmental model was used to fit the plasma concentration of MBF versus time curve for each green sea turtle. The t_1/2λz value, similar for both the dosages (22-28 hr), indicated that the overall rate of elimination of MBF in green sea turtles is relatively slow. The average i.m. F% ranged 88%-103%. MBF is a concentration-dependent drug and the AUC/MIC ratio is the best PK/PD predictor for its efficacy. The MBF dosage of 4 mg/kg appeared to produce an appropriate value of the PK-PD surrogate that predicts antibacterial success for disease caused by susceptible bacteria. In contrast, i.m. administration of MBF at a dosage of 2 mg/kg b.w. was not found to produce a suitable PK-PD surrogate index. However, further studies of multiple doses and plasma binding proteins are warranted to confirm an appropriate dosage regimen.

Pharmacokinetics of injectable marbofloxacin after intravenous and intramuscular administration in red-eared sliders (Trachemys scripta elegans)

Fluoroquinolone antibacterial drugs are currently used in reptilian medicine because of their broad spectrum of activity including the most frequent pathogens of these species. The disposition kinetics of marbofloxacin (MBX) at a single dose of 2 mg/kg were determined in healthy red-eared sliders after intravenous (IV) and intramuscular (IM) administration. The influence of renal portal system on the bioavailability of the drug was investigated by using forelimb and hindlimb as IM injection sites. Apparent volume of distribution at steady-state (V_ss ) and systemic clearance (Cl) of marbofloxacin after IV administration were estimated to be 48.21 ± 5.42 ml/kg and 23.38 ± 2.90 ml/hr·kg, respectively. The absolute bioavailabilities after IM route were 45.96% (forelimb) and 52.09% (hindlimb). The lack of statistically significant differences in most of the pharmacokinetic parameters after the two IM injection sites suggests a negligible influence of renal portal system in clinical use of MBX, although the C_max after IM_fore administration is advantageous, having into account the concentration-dependent action of this antibiotic. The absence of visible adverse reactions in the animals and the advantageous pharmacokinetic properties suggest the possibility of its safe and effective clinical use in red-eared sliders.

Pharmacokinetics of ceftriaxone in freshwater crocodiles (Crocodylus siamensis) after intramuscular administration at two dosages

One of the major obstacles to the successful treatment of infectious disease in freshwater crocodile species is incorrect dosing of antibiotics. There are few reports on pharmacokinetics and dosage regimens of antimicrobial drugs in crocodiles. The purpose of the present study was to clarify the pharmacokinetic characteristics of ceftriaxone (CEF) in Siamese freshwater crocodiles (Crocodylus siamensis). Freshwater crocodiles, Crocodylus siamensis, in breeding farms were treated with a single intramuscular administration of CEF at two dosages, 12.5 and 25 mg/kg body weight (b.w.). Blood samples were collected at preassigned times up to 168 hr. The plasma concentrations of CEF were measured by a validated method through liquid chromatography tandem-mass spectrometry. CEF plasma concentrations were quantified up to 72 and 96 hr after low- and high-dose administration, respectively. The C_max values of CEF were 24.61 ± 5.15 µg/ml and 26.39 ± 2.81 µg/ml at dosages of 12.5 and 25 mg/kg b.w., respectively. The AUC_last values increased in a dose-dependent fashion. The half-life values were not statistically different between the groups (around 20 hr). The average binding percentage of CEF to plasma protein was 53.78 ± 2.11%. Based on the pharmacokinetic data, susceptibility break-point and the surrogate PK-PD index (T > MIC, 0.2 μg/ml), i.m. administration of CEF at a dose of 12.5 mg/kg b.w. might be appropriate for initiating treatment of susceptible bacterial infections in freshwater crocodiles.

Pharmacokinetics of enrofloxacin and its metabolite ciprofloxacin in freshwater crocodiles (Crocodylus siamensis) after intravenous and intramuscular administration

To the best of the authors' knowledge, pharmacokinetic information to establish suitable therapeutic plans for freshwater crocodiles is limited. Therefore, the purpose of this study was to clarify the pharmacokinetic characteristics of enrofloxacin (ENR) in freshwater crocodiles, Crocodylus siamensis, following single intravenous and intramuscular administration at a dosage of 5 mg/kg body weight (b.w.). Blood samples were collected at assigned times up to 168 hr. The plasma concentrations of ENR and its metabolite ciprofloxacin (CIP) were measured by liquid chromatography tandem-mass spectrometry. The concentrations of ENR and CIP in the plasma were quantified up to 144 hr after both the administrations. The half-life was long (43-44 hr) and similar after both administrations. The absolute i.m. bioavailability was 82.65% and the binding percentage of ENR to plasma protein ranged from 9% to 18% with an average of 10.6%. Percentage of CIP (plasma concentrations) was 15.9% and 19.9% after i.v. and i.m. administration, respectively. Based on the pharmacokinetic data, susceptibility break point and PK-PD indexes, i.m. single administration of ENR at a dosage of 5 mg/kg b.w. might be appropriate for treatment of susceptible bacteria (MIC > 1 μg/mL) in freshwater crocodiles, C. siamensis.