Pharmacokinetic behaviour and pharmacokinetic-pharmacodynamic integration of doxycycline in rainbow trout (Oncorhynchus mykiss) after intravascular, intramuscular and oral administrations

OBJECTIVE

Doxycycline (DO) has been used in fish for a long time, but there are some factors that have not yet been clarified regarding its pharmacokinetic (PK) and pharmacodynamic (PD) properties. Therefore, the aim of this study was to investigate the PK and PK/PD targets of DO after 20 mg/kg intravascular (IV), intramuscular (IM) and oral (OR) gavage administration in rainbow trout (Oncorhynchus mykiss).

METHODS

Plasma samples were collected at specific time points and subsequently analysed by HPLC-ultraviolet. The PK/PD indices were calculated based on the MIC90 (Aeromonas hydrophila and Aeromonas sobria) values obtained for the respective bacteria and the PK parameters obtained for DO following both IM and OR administration.

RESULTS

After IV administration, the elimination half-life (t1/2 ʎz), area under the concentration vs. time curve (AUC), apparent volume of distribution at steady-state and total body clearance of DO were 34.81 h, 723.82 h µg/mL, 1.24 L/kg and 0.03 L/kg/h, respectively. The t1/2λz of the DO was found to be 37.39 and 39.78 h after IM, and OR administration, respectively. The bioavailability was calculated 57.02% and 32.29%, respectively, after IM and OR administration. The MIC90 of DO against A. hydrophila and A. sobria was 4 µg/mL. The PK/PD integration showed that DO (20 mg/kg dose) for A. hydrophila and A. sobria with MIC90 ≤4 µg/mL achieved target AUC/MIC value after IM administration.

CONCLUSIONS

These results suggest that when rainbow trout was treated with 20 mg/kg IV and IM administered DO, therapeutically effective concentrations were reached in the control of infections caused by A. hydrophila and A. sobria.

Effect of Dexketoprofen on the Disposition Kinetics of Moxifloxacin in Plasma and Lung in Male and Female Rats

BACKGROUND

The simultaneous use of NSAIDs and antibiotics is recommended for bacterial dis-eases in human and veterinary medicine. Moxifloxacin (MFX) and dexketoprofen (DEX) can be used simul-taneously in bacterial infections. However, there are no studies on how the simultaneous use of DEX affects the pharmacokinetics of MFX in rats.

OBJECTIVES

The aim of this study was to determine the effect of DEX on plasma and lung pharmacokinetics of MFX in male and female rats.

METHODS

A total of 132 rats were randomly divided into 2 groups: MFX (n=66, 33 males/33 females) and MFX+DEX (n=66, 33 females/33 males). MFX at a dose of 20 mg/kg and DEX at a dose of 25 mg/kg were administered intraperitoneally. Plasma and lung concentrations of MFX were determined using the high-performance liquid chromatography-UV and pharmacokinetic parameters were evaluated by non-compartmental analysis.

RESULTS

Simultaneous administration of DEX increased the plasma and lung area under the curve from 0 to 8 h (AUC0-8) and peak concentration (Cmax) of MFX in rats, while it significantly decreased the total body clearance (CL/F). When female and male rats were compared, significant differences were detected in AUC0-8, Cmax, CL/F and volume of distribution. The AUC0-8lung/AUC0-8plasma ratios of MFX were calculated as 1.68 and 1.65 in female rats and 5.15 and 4.90 in male rats after single and combined use, respectively.

CONCLUSION

MFX was highly transferred to the lung tissue and this passage was remarkably higher in male rats. However, DEX administration increased the plasma concentration of MFX in both male and female rats but did not change its passage to the lung. However, there is a need for a more detailed investigation of the difference in the pharmacokinetics of MFX in male and female rats.

Determination of temporal changes in hepatic drug-oxidizing capacity using plasma metabolite/caffeine ratios in non-pregnant and pregnant goats

Caffeine (CF) is a metabolic probe drug used in the determination of the hepatic drug-oxidizing capacity. The aim of this study was to investigate temporal changes in the hepatic drug-oxidizing capacity using plasma metabolite/CF ratios in non-pregnant goats (n = 11) and pregnant goats (n = 23). CF (5 mg/kg, intravenous) was administered in six periods (Period 1-6) with 45 days between two periods. The plasma levels of CF and its metabolites, theophylline (TP), theobromine (TB) and paraxanthine (PX), were determined by HPLC-UV. To evaluate hepatic drug-oxidizing capacity in terms of enzymes that play a role in CF metabolism, the plasma metabolic ratios including TB/CF, PX/CF, TP/CF and TB + PX + TP/CF were determined at 10 h following CF administration. Plasma metabolite/CF ratios were similar between non-pregnant and pregnant goats. However, plasma metabolite/CF ratios in Period 3 (45 days in pregnant goats) were significantly higher than those other periods in both pregnant and non-pregnant goats. The effect of pregnancy may not be observed on drugs that are substrates of enzymes involved in CF metabolism in goats.

Pharmacokinetics, Tissue Residues, and Withdrawal Times of Oxytetracycline in Rainbow Trout (Oncorhynchus mykiss) after Single- and Multiple-Dose Oral Administration

The aim of this study was to compare the pharmacokinetics of oxytetracycline (OTC) following single- (60 mg/kg) and multiple-dose oral administrations (60 mg/kg, every 24 h for 7 days) in rainbow trout. It also aimed to determine bioavailability after a single dose and tissue residues and withdrawal times after multiple doses. This study was carried out on 420 rainbow trout at 9 ± 0.8 °C. This study was carried out in two stages: single-dose (intravascular and oral) and multiple-dose treatment. The OTC concentrations in plasma and tissues were measured by high-performance liquid chromatography and analyzed by a non-compartmental method. The withdrawal time (WT) was estimated using the WT 1.4 software. OTC exhibited a long terminal elimination half-life (t1/2ʎz) after IV and oral administration. The oral bioavailability of OTC was very low (2.80%). In multiple-dose treatment, t1/2ʎz, the area under the plasma concentration-time curve and peak plasma concentration increased significantly after the last day compared to the first day. OTC showed strong accumulation after multiple doses with a value of 5.33. OTC concentrations were obtained in the order liver > kidney > muscle+skin > plasma. At 9 ± 0.8 °C, the WT calculated for muscle+skin was 56 days for Europe and 50 days for China, respectively. The t1/2ʎz (68.94 h) and time (68 h) above the 1 µg/mL MIC following a single OTC dose may support the extension of the 24 h dosing interval following multiple dosing. However, further studies are required to determine the optimal dosage regimen in multiple-dose OTC treatment in the treatment of infections caused by susceptible pathogens.

Pharmacokinetics of meloxicam following intravenous administration at different doses in sheep

The aim of this study is to determine the pharmacokinetic change after intravenous administration of meloxicam at doses of 0.5, 1 and 2 mg/kg to sheep. The study was carried out on six Akkaraman sheep. Meloxicam was administered intravenously to each sheep at 0.5, 1, and 2 mg/kg doses in a longitudinal pharmacokinetic design with a 15-day washout period. Plasma concentrations of meloxicam were determined using the high performance liquid chromatography-ultraviolet, and pharmacokinetic parameters were evaluated by non-compartmental analysis. Meloxicam was detected up to 48 h in the 0.5 mg/kg dose and up to 96 h in the 1 and 2 mg/kg doses. As the dose increased from 0.5 to 2 mg/kg, terminal elimination half-life, and dose normalized area under the concentration versus time curve increased and total clearance decreased. Compared to the 1 mg/kg dose, it was determined that Vdss decreased and C0.083h increased in the 2 mg/kg dose. Meloxicam provided the therapeutic concentration of >0.39 μg/mL reported in other species for 12, 48 and 96 h at 0.5, 1 and 2 mg/kg doses, respectively. These results show that meloxicam exhibits non-linear pharmacokinetics and will achieve unpredictable plasma concentrations when administered IV for a rapid effect at dose of ≥1 mg/kg in sheep.

Pharmacokinetics of letrozole and effects of its increasing doses on gonadotropins in ewes during the breeding season

Letrozole is a non-steroidal, third-generation aromatase inhibitor used in humans. Although letrozole is not approved for use in animals, it is used off-label in cases of synchronization and infertility. The aim of this study was to determine the pharmacokinetics of letrozole after a single intravenous administration at three different doses in ewes during the breeding season and its effect on gonadotropins (luteinizing hormone (LH) and follicle-stimulating hormone (FSH)) at the beginning of proestrus. The study was carried out on 24 healthy Merino ewes. Ewes were randomly divided into four groups (n = 6) as control, 0.5, 1, and 2 mg/kg. Plasma concentrations of letrozole were measured using HPLC-UV and were analyzed by non-compartmental analysis. LH and FSH concentrations were measured with a commercial ELISA kit. The terminal elimination half-life (t1/2ʎz ) was significantly prolonged from 11.82 to 18.44 h in parallel with the dose increase. The dose-normalized area under the concentration-time curve (AUC) increased, and total body clearance (ClT ) decreased at the 1 and 2 mg/kg doses (0.05 L/h/kg) compared with the 0.5 mg/kg dose (0.08 L/h/kg). There were no differences in the volume of distribution at steady-state and initial (C0.083h ) plasma concentration values between dose groups. The decreased ClT , prolonged t1/2ʎz, and increased AUC at increasing doses showed the nonlinear kinetic behavior of letrozole. Letrozole significantly reduced LH concentration without affecting FSH concentration at all doses. As a result, letrozole has the potential to be used in synchronization methods and manipulation of the follicular waves due to its effect on LH secretion.

Pharmacokinetics and bioavailability of meloxicam in Pekin ducks following intravenous, intramuscular and oral administration

OBJECTIVE

To determine the pharmacokinetics and bioavailability of meloxicam following intravenous (IV), intramuscular (IM), and oral administrations at a dose of 1.0 mg kg-1 in Pekin ducks.

STUDY DESIGN

Randomized experimental trial.

ANIMALS

A total of 18 clinically healthy male Pekin ducks.

METHODS

Pekin ducks were randomly assigned to three groups of six ducks: IV, IM and oral. Meloxicam (1.0 mg kg-1) was administered to each Pekin duck. A non-compartmental analysis was used to evaluate pharmacokinetic parameters.

RESULTS

No local or systemic adverse effects were observed in any bird. Meloxicam was detected in the plasma up to 120 hours following IV, IM or oral administration. The elimination half-life of the IV route was slightly shorter than that of the IM and oral routes (p < 0.05). Following IV administration, volume of distribution at steady state and total clearance were 133.17 mL kg-1 and 6.68 mL kg-1 hour-1, respectively. The mean absorption time was 2.29 hours for IM and 1.13 hours for oral route. There were significant differences between IM and oral administration for the peak plasma concentration (Cmax), time to reach Cmax and bioavailability (p < 0.05).

CONCLUSIONS AND CLINICAL RELEVANCE

Meloxicam showed long elimination half-life and high bioavailability following IM and oral administration. Meloxicam in Pekin ducks provided the effective therapeutic concentration indicated in other species for up to 48 hours. However, there is a need to determine the clinical efficacy of meloxicam in Pekin ducks.

Age-related changes in the pharmacokinetics of meloxicam after intravenous administration in sheep

The pharmacokinetics of meloxicam was studied in 1-, 6-, and 12-month-old sheep following a single intravenous (i.v.) dose of 1 mg/kg. The experiments were carried out when the Romanov sheep were 1 month old (7.93 ± 0.91 kg), 6 months old (27.47 ± 4.91 kg), and 12 months old (37.10 ± 3.64 kg). Meloxicam concentration in plasma was determined by high-performance liquid chromatography and the data collected were evaluated by non-compartmental kinetic analysis. Meloxicam was detected in the plasma up to 72 h following i.v. administration in all age groups. The volume of distribution at steady state (Vdss ) and total body clearance (ClT ) were significantly higher in 1-month-old (304.87 mL/kg and 16.57 mL/h/kg) than in 12-month-old (193.43 mL/kg and 10.50 mL/h/kg) sheep. The area under the concentration-time curve from 0 to 72 h value of meloxicam was lower in 1-month-old (58.51 h*μg/mL) compared to 12-month-old (92.59 h*μg/mL) sheep. There was no difference in t1/2ʎz value in different age groups. The body extraction ratio values for meloxicam ranged from 0.0186 to 0.0719 after i.v. administration in all age groups. Meloxicam showed an increase in plasma concentration and a decrease in Vdss and ClT in 12-month-old compared to 1-month-old sheep. Compared to 1-month-old and 12-month-old sheep, there was no difference in these parameters in 6-month-old sheep. Because the age of sheep has an influence on the pharmacokinetics of meloxicam, dosage apparently may need to be adjusted for age.

Effect of Xylazine on Pharmacokinetics and Physiological Efficacy of Intravenous Carprofen in Castrated Goats Kids

Carprofen can be used in the castration process of male goats due to its low side effects, long elimination half-life, and long-term effect. However, no studies were found on the pharmacokinetics and physiological efficacy of carprofen when employed for castration in male goats. The aim of this study was to determine the effect of xylazine (0.05 mg/kg, intramuscular) on the pharmacokinetics and physiological efficacy following intravenous administration of carprofen (4 mg/kg, intravenous) in male goat kids castrated using the burdizzo method. Thirty male Kilis goat kids (5-6 months and 18-30 kg of body weight) were randomly assigned to five groups (n = 6) as follows: healthy control (HC), castration control (CAST), castration+carprofen (CAST+CRP), castration+xylazine (CAST+XYL), and castration+xylazine+carprofen (CAST+XYL+CRP). Plasma concentrations of carprofen were analyzed via a non-compartmental method. Physiological parameters including serum cortisol, scrotal temperature, rectal temperature, and scrotal circumference were determined. Xylazine caused a decrease in the volume of distribution and clearance and an increase in the area under the curve of carprofen in CAST+XYL+CRP group (p < 0.05). The mean cortisol concentrations in CAST+CRP and CAST+XYL remained lower compared to CAST (p < 0.05). The mean cortisol concentrations in CAST+XYL+CRP were lower than in CAST+CRP and CAST+XYL (p < 0.05). In addition, the effect of carprofen administration alone on reducing the initial cortisol response to castration was observed from 6 to 48 h, while in combination with xylazine, it was observed immediately up to 48 h. No treatment differences were observed in rectal temperature, scrotal temperature, and scrotal circumference (p > 0.05). Xylazine caused an increase in plasma concentration and a decrease in clearance of carprofen after co-administration. However, when the effect of the combined administration of carprofen with xylazine on cortisol is evaluated, their combined use in castration process may be beneficial.

Effects of Temperature on the Pharmacokinetics, Tissue Residues, and Withdrawal Times of Doxycycline in Rainbow Trout (Oncorhynchus mykiss) following Oral Administration

The purpose of this study was to compare the pharmacokinetics, tissue residues, and withdrawal times of doxycycline after oral administration in rainbow trout reared at 10 and 17 °C. Fish received a 20 mg/kg oral dose of doxycycline after a single or 5-day administration. Six rainbow trout were used at each sampling time point for plasma and tissue samples, including liver, kidney, and muscle and skin. The doxycycline concentration in the samples was determined using high-performance liquid chromatography with ultraviolet detector. The pharmacokinetic data were evaluated by non-compartmental kinetic analysis. The WT 1.4 software program was used to estimate the withdrawal times. The increase of temperature from 10 to 17 °C shortened the elimination half-life from 41.72 to 28.87 h, increased the area under the concentration-time curve from 173.23 to 240.96 h * μg/mL, and increased the peak plasma concentration from 3.48 to 5.50 μg/mL. At 10 and 17 °C, the doxycycline concentration was obtained in liver > kidney > plasma > muscle and skin. According to the MRL values stated for muscle and skin in Europe and China (100 μg/kg) and in Japan (50 μg/kg), the withdrawal times of doxycycline at 10 and 17 °C were 35 and 31 days, respectively, for Europe and China and 43 and 35 days, respectively, for Japan. Since temperature significantly affected pharmacokinetic behavior and withdrawal times of doxycycline in rainbow trout, temperature-dependent dosing regimens and withdrawal times of doxycycline might be necessary.

The effect of tilmicosin and diclofenac sodium combination on cardiac biomarkers in sheep

The aim of this study was to investigate the cardiotoxic effect of the combination of tilmicosin and diclofenac sodium in sheep. Thirty-two sheep were used and were randomly divided into four equal groups as tilmicosin (T), diclofenac sodium (D), tilmicosin+diclofenac sodium (TD) and control (C) group. Group T received a single dose of tilmicosin, Group D was administered diclofenac sodium once a day for 3 days, and group TD was administered diclofenac and tilmicosin at the same doses as group T and D. Group C received NaCl in a similar way. The blood samples were taken before dosing and at 4th, 8th, 24th and 72nd hour post-dosing for measurement of cardiac markers such as H-FABP, cTn-I, CK-MB. H-FABP level of group TD was found to be significantly (p⟨0.05) higher than of group C at the 8th, 24th and 72nd hour and group D and T at the 72nd hour. cTn-I and CK-MB levels of group TD were found significantly (p⟨0.05) higher compared with other groups. In conclusion, the combined use of tilmicosin and diclofenac in sheep causes an increase in cardiac biomarkers and it can be stated that this combination of drugs may cause cardiac damage.

Comparative Pharmacokinetics of Intravenous Enrofloxacin in One- Six- And Twelve-Month-Old Sheep

BACKGROUND

Enrofloxacin (ENR) is a fluoroquinolone antibiotic approved for use in sheep of all ages. The body composition and metabolic capability change with age. These changes may alter the pharmacokinetics of drugs and thus their effect. Therefore, the pharmacokinetics of drugs need to be established in target- age animals.

OBJECTIVE

To determine the pharmacokinetics of ENR and its active metabolite, ciprofloxacin (CIP), following a single intravenous administration of ENR at a dose of 10 mg/kg in different ages of sheep.

METHODS

The study was carried out in the one-, six- and twelve-month age period of the sheep. A single dose of 10 mg/kg ENR was administered intravenously through the jugular vein to sheep in all age periods. ENR and CIP plasma concentrations were determined using HPLC-UV and analyzed using a non-compartmental method.

RESULTS

ENR was detected in the plasma until 36 h in one-month-old and up to 24 h in other ages. CIP was detected in the plasma up to 24 h in all age groups. The t1/2ʎz and Vdss were significantly higher in one-month-old sheep than in six and twelve-months old sheep. There was no difference in ClT and AUC values in different age groups. AUC0-∞CIP/AUC0-∞ENR ratios were higher in one-month-old than in six- and twelve-months sheep.

CONCLUSION

The most important pharmacokinetic changes associated with aging in sheep are decreased Vdss and t1/2ʎz of ENR and the low ratio metabolizing of ENR to CIP. Pharmacokinetic/pharmacodynamic data showed that ENR after IV administration of 10 mg/kg dose provided the optimal AUC0-24/MIC90 ratios for E. coli, P. multocida and Mycoplasma spp. (>125) with MIC of 0.37 µg/mL and for S. aureus (>30) with MIC of 0.5 µg/mL in all ages of sheep.

Plasma and muscle tissue disposition of enrofloxacin in Nile tilapia (Oreochromis niloticus) after intravascular, intraperitoneal, and oral administrations

The aim of the study was to investigate the plasma and muscle pharmacokinetic of enrofloxacin (ENR) and its active metabolite ciprofloxacin (CIP) in Nile tilapia (Oreochromis niloticus) following single intravascular (IV), intraperitoneal (IP), or oral (PO) administration at 30 ± 1 °C. In this study, 234 healthy Nile tilapia (120-150 g) were used. The fish received a single IV, IP, or PO treatment of ENR at a dose of 10 mg/kg. The plasma and muscle tissue concentrations of ENR and CIP were measured using high-performance liquid chromatography with fluorescence detection and were evaluated using non-compartmental analysis. The elimination half-life, volume of distribution at steady state, and total body clearance of ENR were 21.7 h, 2.69 L/kg, and 0.09 L/h/kg, respectively. The peak plasma concentrations of ENR after IP or PO administration were 6.11 and 4.21 µg/mL at 0.25 and 2 h, respectively. The bioavailability of ENR for IP or PO routes was 78% and 86%, respectively. AUC_{(0-120)muscle}/AUC_{(0-120)plasma} ratios following the IV, IP, or PO administrations were 1.43, 1.49, and 1.07, respectively. CIP was detected after all routes, but the AUC_0-last ratios of CIP to ENR were <1.0% for plasma and muscle. ENR was detected up to 120 h following the IV, IP, or PO administrations. The long residence time of ENR after single IV, IP, or PO administration ensured the plasma concentration was ≥1 × MIC for bacteria with threshold MIC values of 0.92, 0.72, and 0.80 μg/mL over the whole 120 h observed. However, further studies are necessary to determine the optimum pharmacokinetic/pharmacodynamics data of ENR for the treatment of infections caused by susceptible bacteria in tilapia.

Pharmacokinetics of cefquinome in rainbow trout (Oncorhynchus mykiss) after intravascular, intraperitoneal, and oral administrations

This study aimed to determine the pharmacokinetics and bioavailability of cefquinome in rainbow trout (Oncorhynchus mykiss) following intravascular (IV), intraperitoneal (IP), and oral (PO) administrations at 14 ± 1°C. In this study, three hundred and six clinically healthy rainbow trout (110-140 g) were used. The fish received single IV, IP, and PO injections of cefquinome at 10 mg/kg dose. The plasma concentrations of cefquinome were measured using HPLC-UV and were evaluated using non-compartmental analysis. Cefquinome was measured up to 96 h for PO route and 144 h for IV and IP routes in plasma. Following IV administration, t_1/2ʎz , Cl_T , and V_dss were 18.85 h, 0.037 L/h/kg, and 0.84 L/kg, respectively. The C_max of IP and PO routes was 9.75 and 1.64 μg/ml, respectively. The bioavailability following IP and PO administrations was 59.46% and 12.33%, respectively. Cefquinome at 10 mg/kg dose may maintain T > MIC above 40% at 72 and 96 h intervals, respectively, following the IP and IV routes for bacteria with MIC values of ≤2 μg/ml and at 24 h intervals following the PO route for bacteria with MIC value of ≤0.75 μg/ml. However, further studies are needed to determine in vitro and in vivo antibacterial efficacy and multiple dosage regimens of cefquinome against pathogens isolated from rainbow trout.

Pharmacokinetics and bioavailability of danofloxacin in swan geese (Anser cygnoides) following intravenous, intramuscular, subcutaneous, and oral administrations

The aim of this study was to determine the pharmacokinetics and bioavailability of danofloxacin in swan geese (Anser cygnoides) after intravenous (IV), intramuscular (IM), subcutaneous (SC), and oral (PO) administrations at 10 mg/kg dose. In this study, eight clinically healthy swan geese were used. The study was performed in four periods according to a crossover design with a 15 days washout period between two administrations. The plasma concentrations of danofloxacin were analyzed using high-performance liquid chromatograph-ultraviolet detection, and pharmacokinetic parameters were estimated by non-compartmental analysis. Following IV administration, terminal elimination half-life (t_1/2ʎz ), total clearance, and volume of distribution at steady state were 6.03 h, 0.34 L/h/kg, and 2.71 L/h/kg, respectively. After IM, SC, and PO administration, t_1/2ʎz was longer than that after IV administration. The C_max of danofloxacin following IM, SC, and PO administrations was 3.65, 2.76, and 1.98 μg/mL at 0.63, 1, and 2 h, respectively. The bioavailability following IM, SC, and PO administrations was 87.99, 72.77, and 57.68%, respectively. This information may help in the use of danofloxacin in geese, yet the determination of optimal dosage regimen and pharmacodynamic studies are needed.

Pharmacokinetics and bioavailability of carprofen in sheep

The aim of this study was to determine the pharmacokinetics and bioavailability of carprofen in sheep following single intravenous (IV), intramuscular (IM), subcutaneous (SC), and oral (PO) administrations of a parenteral formulation at a dose of 4 mg/kg. A total of eight sheep were used for the investigation. The study comprised four periods, according to a crossover design with a 21-day washout period between treatments. Plasma concentrations of carprofen were measured using HPLC-UV. Pharmacokinetic parameters were estimated by non-compartmental model analysis. Following IV administration, t_1/2ʎz , Cl_T , and V_dss were 43.36 h, 1.98 ml/h/kg, and 121.36 ml/kg, respectively. The C_max(obs) was 26.57 mg/ml for the IM, 23.76 mg/ml for the SC, and 15.90 mg/ml for the PO. The bioavailability following IM, SC, and PO administrations was 75.47%, 82.00%, and 62.51%, respectively. Plasma creatine kinase activity increased significantly at 3, 6, and 12 h following IM administration of carprofen. Despite differences in plasma concentrations and bioavailability among administration routes, carprofen at 4 mg/kg dose may provide the plasma concentration (>1.5 μg/ml) needed for analgesic effect during 144 h in all routes. However, because of the slow absorption rate after SC and PO routes, the IV route may be preferred primarily for the rapid onset in the analgesic and anti-inflammatory effect of carprofen in sheep. Despite the favorable kinetics, the muscle damage caused by IM injection limits use of carprofen via IM route.

Pharmacokinetics of carprofen following single and repeated intravenous administrations of different doses in sheep

The aim of this study was to determine the pharmacokinetics of carprofen following single and repeated intravenous (IV) administrations at 1.4 and 4 mg/kg doses in sheep. The study was carried out on twelve sheep in two experiments as single- and multiple-dose pharmacokinetics. In experiment 1, carprofen was administered via IV at single doses of 1.4 (n = 6) and 4 mg/kg (n = 6) in a randomized parallel design. In experiment 2, the same dose groups in experiment 1 following the 21-day washout period received intravenously carprofen every 24 h for 5 days. Plasma concentrations were measured using high-performance liquid chromatography-UV and analyzed by a two-compartment open model. After the single administration of 1.4 mg/kg dose, the t_1/2α , t_1/2el , MRT, Cl_T , V_dss , and AUC were 0.62 h, 27.57 h, 38.78 h, 2.72 ml/h/kg, 105.26 ml/kg, and 515.12 h*μg/ml, respectively. Carprofen at a single dose of 4 mg/kg showed prolonged t_1/2el and MRT, and increased V_dss . On day 5 after the repeated administration of the 1.4 mg/kg dose, the t_1/2α , t_1/2el , MRT, Cl_T , V_dss , and AUC were 1.12 h, 57.48 h, 82.18 h, 0.55 ml/h/kg, 45.43 ml/kg, and 2532 h*μg/ml, respectively. Carprofen at a repeated dose of 4 mg/kg showed increased Cl_T and V_dss and decreased AUC/dose. Although the long t_1/2ʎz in single and multiple IV dose studies suggest the possibility of its effective use, the IV route may not be practical in sheep. Therefore, oral and subcutaneous routes of carprofen in sheep would be more valuable in clinical settings.

Pharmacokinetics of intravenous meloxicam, ketoprofen and tolfenamic acid in chukar partridge (Alectoris chukar)

1. The aim of this study was to determine the pharmacokinetics of meloxicam (MLX, 1 mg/kg body weight (BW)), ketoprofen (KETO, 2 mg/kg BW), and tolfenamic acid (TA, 2 mg/kg BW) in chukar partridge (Alectoris chukar) following intravenous (IV) administration.2. Twenty-four healthy chukar partridges were randomly divided into three equal groups (n = 8) as MLX, KETO and TA. Plasma concentrations of MLX, KETO and TA were measured using high-performance liquid chromatography-ultraviolet detection and analysed using non-compartmental analysis.3. No adverse effects were determined in chukar partridges after IV administration of MLX, KETO and TA. MLX, KETO and TA were detected in plasma up to 10, 12 and 12 h, respectively. The terminal elimination half-life of MLX, KETO and TA was 1.22, 1.77 and 1.95 h, respectively. MLX, KETO and TA exhibited volumes of distribution at a steady-state of 0.03, 0.23 and 0.41 l/kg BW, respectively. The total plasma clearance of MLX, KETO and TA was 0.02, 0.11 and 0.15 l/h/kg, respectively. The extraction ratios for MLX, KETO and TA were calculated as 0.002, 0.011 and 0.016, respectively.4. MLX, KETO and TA offer treatment in chukar partridges for various conditions with an absence of adverse reactions and properties such as short elimination half-life and low volume of distribution. However, there is a need to establish the safety and adverse effects of repeated administration, pharmacokinetics of other administration routes and pharmacological efficacy of MLX, KETO and TA in chukar partridges.

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.

Effect of ketoprofen on intravenous pharmacokinetics of ganciclovir in chukar partridges (Alectoris chukar)

The aim of the study was to determine the effect of ketoprofen (2 mg/kg) on the intravenous pharmacokinetics of ganciclovir (10 mg/kg) in chukar partridges (Alectoris chukar). Eight clinically healthy partridges were used in the study. The study was performed in two periods using a cross-over design following a 15-day drug washout period. Plasma concentrations of ganciclovir were determined using the high-pressure liquid chromatography-ultraviolet detector and analyzed by non-compartmental analysis. The elimination half-life (t_1/2ʎz ), area under the concentration-time curve (AUC_0-∞ ), total body clearance, and volume of distribution at steady state of ganciclovir were 1.63 h, 33.22 h*μg/ml, 0.30 L/h/kg, and 0.53 L/kg, respectively. Ketoprofen administration increased the t_1/2ʎz and AUC_0-∞ of ganciclovir by 78% and 108%, respectively, and while decreased Cl_T by 53%. The increased plasma concentration and prolonged elimination half-life of ganciclovir caused by ketoprofen may result in the prolonged duration of action and therapeutic effect of ganciclovir. However, the concomitant use requires determination of the pharmacokinetics of ketoprofen and the safety of both drugs.

Pharmacokinetics and Pharmacokinetic/Pharmacodynamic Integration of Enrofloxacin Following Single Oral Administration of Different Doses in Brown Trout (Salmo trutta)

Simple Summary

The pharmacokinetic/pharmacodynamic studies report the use of enrofloxacin at higher doses than 10 mg/kg in fish. Pharmacokinetic data for increasing doses of enrofloxacin can facilitate suggestions regarding the dose for the treatment of infections in brown trout. This study aims to determine single oral pharmacokinetics of enrofloxacin at 10, 20, and 40 mg/kg doses in brown trout and pharmacodynamics against Aeromonas hydrophila and A. sobria. Enrofloxacin exhibited non-linear and dose-disproportional pharmacokinetics. The long action of enrofloxacin following the single oral administration at 10 and 20 mg/kg doses may provide the unique dosage regimen to minimize handling, thereby reducing the cost of administration and stress in brown trout.

Abstract

The pharmacokinetic of enrofloxacin was investigated in brown trout (Salmo trutta) following oral administration of 10, 20, and 40 mg/kg doses at 11 ± 1.5 °C. Furthermore, MICs of enrofloxacin against Aeromonas hydrophila and A. sobria were determined. The plasma concentrations of enrofloxacin and ciprofloxacin were determined using HPLC–UV and analyzed by non-compartmental method. Following oral administration at dose of 10 mg/kg, total clearance (CL/F), area under the concentration–time curve (AUC_0−∞) and peak plasma concentrations (C_max) were 41.32 mL/h/kg, 242.02 h*μg/mL and 4.63 μg/mL, respectively. When compared to 10 mg/kg dose, the dose-normalized AUC_0–∞ and C_max were increased by 56.30% and 30.08%, respectively, while CL/F decreased by 38.4% at 40 mg/kg dose, suggesting the non-linearity. Ciprofloxacin was not detected in the all of plasma samples. The MIC values of enrofloxacin were ranged 0.0625–4 μg/mL for A. hydrophila and 0.0625–2 μg/mL for A. sobria. The oral administration of enrofloxacin at 10 (for 192 h) and 20 (for 240 h) mg/kg doses provided the AUC of enrofloxacin equal to 1.23 and 1.96-fold MICs, respectively, for A. hydrophila and A. sobria with the MIC₉₀ values of 1 µg/mL. However, further researches are needed on the PK/PD study of enrofloxacin for the successful treatment of infections caused by A. hydrophila and A. sobria in brown trout.

The pharmacokinetics of letrozole and its effect on gonadotropins in anestrous ewes

The aim of this study was to determine the pharmacokinetics of letrozole and its effect on FSH and LH concentrations after single (IV, IM, SC) and repeated IV doses in anestrous ewes. This study was conducted in experiments 1 and 2 by randomly dividing 24 healthy Akkaraman ewes in anestrus into two equal groups. In experiment 1, the pharmacokinetics of letrozole following single IV, IM, and SC administration at 1 mg/kg dose and its effect of a single IV dose on plasma FSH and LH concentration were determined. In experiment 2, the effect of repeated IV doses of letrozole on FSH and LH concentrations was established. Plasma concentration of letrozole was measured using high-performance liquid chromatography, and pharmacokinetic parameters were calculated by non-compartmental analysis. FSH and LH concentrations were quantified using ELISA. The elimination half-life (t_1/2ʎz) for IV, IM, and SC routes were 9.94, 37.29, and 41.07 h, respectively. The IV route for letrozole had a total clearance of 0.11 L/h/kg and a volume of distribution at a steady state of 1.50 L/kg. The peak plasma concentration was 0.11 μg/mL for the IM route and 0.14 μg/mL for the SC routes. The bioavailability was 55.18% for the IM route and 75.34% for the SC route. Letrozole following single and repeated (every 24 h for 3 days) IV administrations at 1 mg/kg dose did not affect LH concentration in anestrous ewes but caused an increase in the FSH concentration. This increase in FSH concentration may create a potential for the use of letrozole in ovarian superstimulation protocols. Favorable pharmacokinetic properties (long t_1/2ʎz and good bioavailability) of letrozole for IM and SC routes require further investigation before use in estrus induction or estrus synchronization protocols in sheep.

Pharmacokinetics of furosemide in goats following intravenous, intramuscular, and subcutaneous administrations

Furosemide, a loop diuretic drug, is recommended for use in cases of edema, ascites, congestive heart failure, toxicosis, and acute renal failure in goats. However, its pharmacokinetics and bioavailability have not been reported yet in this species. The aim of this study was to determine the pharmacokinetics and bioavailability of furosemide in goats following intravenous (IV), intramuscular (IM), and subcutaneous (SC) administrations at a dose of 2.5 mg/kg. Six clinically healthy goats received furosemide by each route in a three-way crossover pharmacokinetic design with a 15-day washout period between administrations. The plasma concentrations of furosemide were determined using the high-performance liquid chromatography-UV method and analyzed by non-compartmental analysis. The elimination half-life following IV, IM, and SC administration was 0.71 (0.67-0.76) h, 0.69 (0.61-0.74) h, and 0.70 (0.67-0.79) h, respectively. The volume of distribution at steady state and total clearance for the IV route were 0.17 (0.16-0.19) L/kg and 0.30 (0.27-0.33) L/h/kg, respectively. The peak plasma concentrations of furosemide following IM and SC administrations were 11.19 (10.33-11.95) and 6.49 (5.92-7.00) μg/ml at 0.23 (0.16-0.25) and 0.39 (0.33-0.42) h, respectively. The bioavailability was 109.84 (104.92-116.99)% and 70.80 (55.77-86.67)% for the IM and SC routes, respectively. The pharmacokinetics of furosemide following the IV, IM, and SC administrations in goats demonstrated significant differences, which may have clinical and toxicological implications requiring further investigations.

Effect of ketoprofen and tolfenamic acid on intravenous pharmacokinetics of ceftriaxone in sheep

In this study, the pharmacokinetics of ceftriaxone (40 mg/kg) was determined following a single intravenous (IV) administration of ceftriaxone alone and co-administration with ketoprofen (3 mg/kg) or tolfenamic acid (2 mg/kg) in sheep. Eight healthy Akkaraman sheep (2.4 ± 0.3 years and 44 ± 4 kg of body weight) were used. The study was carried out according to the longitudinal design in three periods with a 15-day washout period between administrations. In the first period, sheep received ceftriaxone alone via an IV injection. In the second and third periods, the same sheep received ceftriaxone in combination with ketoprofen and tolfenamic acid, respectively. Plasma concentrations of ceftriaxone were assayed by high-performance liquid chromatography and analyzed using non-compartmental analysis. Following the administration of ceftriaxone alone, the elimination half-life (t_1/2ʎz ), area under the plasma concentration-time curve from zero (0) hours to infinity (∞) (AUC_0-∞ ), total clearance (Cl_T ), and volume of distribution at steady state were 1.42 h, 182.41 h*µg/ml, 0.22 L/h/kg, and 0.17 L/kg, respectively. While ketoprofen and tolfenamic acid significantly increased the t_1/2ʎz and AUC_0-∞ of ceftriaxone, they significantly reduced the Cl_T . Ceftriaxone (40 mg/kg, IV) in concurrent use with ketoprofen and tolfenamic acid can be administrated at the 12 h dosing intervals to maintain T> minimum inhibitory concentration (MIC) values above 60% in the treatment of infections caused by susceptible pathogens with the MIC value of ≤0.75 and ≤1 μg/mL, respectively, in sheep with an inflammatory condition.

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 meloxicam, carprofen, and tolfenamic acid after intramuscular and oral administration in Japanese quails (Coturnix coturnix japonica)

The aim of this study was to determine the pharmacokinetics of meloxicam (MLX), carprofen (CRP), and tolfenamic acid (TA) in Japanese quails (Coturnix coturnix japonica) following intramuscular (IM) and oral administration at doses of 1, 10, and 2 mg/kg, respectively. A total of 72 quails were randomly divided into 3 equal groups as MLX, CRP, and TA. Each group was separated into two sub-groups that received IM and oral administration of each drug. Plasma concentrations of MLX, CRP, and TA were determined using HPLC-UV and analyzed by non-compartmental method. The t_1/2ʎz and MRT of MLX, CRP, and TA after oral administration were similar to those after IM administration. The V_darea /F of MLX, CRP, and TA after IM administration was 0.28, 2.05, and 0.20 L/kg. The Cl/F of MLX, CRP, and TA after IM administration was 0.12, 0.19, and 0.09 L/h/kg. MLX, CRP, and TA after oral administration showed significantly lower C_max and longer T_max compared with IM administration. The relative bioavailability of MLX, CRP, and TA following oral administration in quails was 76.13%, 61.46%, and 57.32%, respectively. The IM and oral route of MLX, CRP, and TA can be used for the treatment of various conditions in quails. However, further research is necessary to determine the pharmacodynamics and safety of MLX, CRP, and TA before use in quails.

A novel herbal immunostimulant for rainbow trout (Oncorhynchus mykiss) against Yersinia ruckeri

In this 21-day study, we examined the effects of the aqueous methanolic extract of thin-skinned plum (Prunus domestica) on growth, immune response and resistance to a pathogenic bacterium, Yersinia ruckeri in rainbow trout (Oncorhynchus mykiss). Fish were fed with diets containing thin-skinned plum extract doses as 0 (Control) 0.1 (PD01), 0.5 (PD05) and 1% (PD1) ad libitum twice in a day. At the end of the study, growth was affected positively but not significantly. Feed conversion ratio (FCR) was decreased in the PD01 group (P < 0.05). There were elevated respiratory burst and potential bacterial killing activities on the 7th day in the PD1 fish group. No differences were observed in lysozyme activity (P > 0.05). An increased myeloperoxidase activity was recorded on the 14th day of study. Expression of interleukin and COX-2 genes was elevated on the 7th day of study in the kidney and intestine of treated fish. Histological results indicated no marked changes in organs (gill, kidney, liver and spleen) of PD treated fish groups. Challenge results of fish in all plum extract-treated groups showed an increased survival rate against Y. ruckeri (P < 0.05). This study indicated that the thin-skinned plum aqueous methanolic extract could improve innate immunity, survival against Y. ruckeri and decrease the FCR level.

Pharmacokinetics of tolfenamic acid after different administration routes in geese (Anser cygnoides)

The pharmacokinetics and bioavailability of tolfenamic acid were determined in geese (Anser cygnoides) following intravenous (IV), intramuscular (IM), subcutaneous (SC), and oral administrations at 2 mg/kg dose. In this study, eight healthy geese (3.5 ± 0.5 kg) were used. The study was performed in four periods according to a crossover design with a 15-day washout period between two administrations. The plasma concentrations of tolfenamic acid were analyzed using HPLC-UV, and pharmacokinetic parameters were calculated by noncompartmental analysis. The elimination half-life was 1.73, 2.51, 2.34, and 2.31 hr for IV, IM, SC, and oral routes, respectively. The volume of distribution at steady state and total clearance after IV administration were 0.25 L/kg and 0.16 L hr^-1  kg^-1 , respectively. The peak plasma concentrations of tolfenamic acid after IM, SC, and oral administrations were 4.89, 2.94, and 2.92 μg/ml at 0.25, 0.75, and 1 hr, respectively. The bioavailability was 87.91, 77.87, and 76.03% for the IM, SC, and oral routes, respectively. Tolfenamic acid, which exhibits the good bioavailability and plasma concentration following IM, SC, and oral administrations at 2 mg/kg dose, may be useful in the treatment of inflammatory disease conditions in geese.

Pharmacokinetics of tolfenamic acid in goats after different administration routes

The aim of this study was to determine the pharmacokinetics and bioavailability of tolfenamic acid in goats after intravenous (IV), intramuscular (IM), subcutaneous (SC), and oral (PO) administrations at 2 mg/kg dose. In this study, eight clinically healthy goats were used. The study comprised four periods, according to a crossover design with at least a 15-day washout period between treatments. Plasma concentrations of tolfenamic acid were determined by HPLC-UV, and the pharmacokinetic parameters were estimated using a non-compartmental method. Following IV administration, terminal elimination half-life, volume of distribution at steady state, and total clearance were 1.60 h, 0.37 L/kg, and 0.27 L/h/kg, respectively. The mean peak plasma concentration following IM, SC, and PO administrations was 1.77, 1.22, and 0.30 μg/ml, respectively. The mean bioavailability following IM, SC, and PO administrations was 64.46, 55.43, and 19.46%, respectively. The PO route, which exhibits both the low plasma concentration and bioavailability, is not recommended in goats. The IV, IM, and SC routes, which show comparable pharmacokinetic profiles, may be proposed for use in goats. However, the multi-dose and pharmacodynamic studies are necessary to establish more accurately its safety and efficacy in the goat.

Pharmacokinetics and bioavailability of furosemide in sheep

The pharmacokinetics and bioavailability of furosemide were determined following intravenous (IV), intramuscular (IM), and subcutaneous (SC) administrations at 2.5 mg/kg dose in sheep. The study was conducted on six healthy sheep in a three-way, three-period, crossover pharmacokinetic design with a 15-day washout period. In first period, furosemide was randomly administered via IV to 2 sheep, IM to 2 sheep and SC to 2 sheep. In second and third periods, each sheep received furosemide via different routes of administration with the 15-day washout period. Plasma concentrations were determined using a high-performance liquid chromatography assay and analyzed by noncompartmental method. The mean total clearance and volume of distribution at steady state following IV administration were 0.24 L h^-1  kg^-1 and 0.17 L/kg, respectively. The elimination half-life was similar for all administration routes. The mean peak plasma concentrations of IM and SC administration were 10.33 and 3.18 μg/ml at 0.33 and 0.42 hr, respectively. The mean bioavailability of IM and SC administration was 97.91% and 37.98%, respectively. The IM injection of furosemide may be the alternative routes in addition to IV. However, further research is required to determine the effect of dose and route of administration on the clinical efficacy of furosemide in sheep.

Pharmacokinetics, bioavailability and tissue residues of doxycycline in Japanese quails (Coturnix coturnix japonica) after oral administration

This study aimed to determine the bioavailability, tissue residue and withdrawal time of doxycycline after oral administration in Japanese quails (Coturnix coturnix japonica). Japanese quails received doxycycline at 20 mg/kg dose following either single intravenous or oral administration, or 5-day oral administration. Doxycycline concentrations in plasma, liver, kidney, muscle, and skin + fat were determined using high-performance liquid chromatography-ultraviolet. The Withdrawal Time v1.4 software was used to calculate withdrawal times. Following single oral administration, terminal elimination half-life, area under the concentration-time curve from 0 to infinitive time, peak plasma concentration (C_max) and time to reach C_max were 10.98 h, 215.84 (h*µg)/mL, 15.33 μg/mL, and 2 h, respectively. The oral bioavailability was 25.84% in quails. In this study, the mean doxycycline concentration was below the maximum residue limit (MRL) at day 4 in skin + fat (0.120 µg/g), and at day 5 in kidney (0.41 µg/g), liver (0.26 µg/g), and muscle (<0.05 µg/g lowest limit of quantification). The highest concentrations of doxycycline after 5-day oral administration were found in kidney compared with other tissues and plasma. These results indicate that the withdrawal times required for doxycycline to reach concentrations <MRLs after 5-day oral administration at 20 mg/kg dose in Japanese quail are 6 days in Europe and China and 9 days in Japan.

Effect of ketoprofen co-administration on pharmacokinetics of cefquinome following repeated administration in goats

The pharmacokinetics of cefquinome (2 mg/kg every 24 hr for 5 days) was determined following intramuscular administration alone and co-administration with ketoprofen (3 mg/kg every 24 hr for 5 days) in goats. Six goats were used for the study. In the study, the crossover pharmacokinetics design with 20-day washout period was performed in two periods. Plasma concentrations of cefquinome were assayed using high-performance liquid chromatography by ultraviolet detection. The mean terminal elimination half-life (t_1/2ʎz ), area under the concentration-time curve (AUC_0-24 ), peak concentration (C_max ), apparent volume of distribution (V_darea /F), and total body clearance (CL/F) of cefquinome after the administration alone were 4.85 hr, 11.06 hr*µg/ml, 2.37 µg/mL, 1.23 L/kg, and 0.17 L/h/kg after the first dose, and 5.88 hr, 17.01 hr*µg/mL, 3.04 µg/mL, 0.95 L/kg, and 0.11 L/h/kg after the last dose. Ketoprofen significantly prolonged t_1/2ʎz of cefquinome, increased AUC_0-24 and C_max , and decreased V_darea /F and CL/F. Cefquinome exhibited low accumulation after the administration alone and in combination with ketoprofen. These results indicated that ketoprofen prolonged the elimination of cefquinome in goats. The 24-hr dosing intervals at 2 mg/kg dose of cefquinome, which co-administered with ketoprofen, may maintain T> minimum inhibitory concentration (MIC) values above 40% in the treatment of infections caused by susceptible pathogens with the MIC value of ≤0.75 μg/ml in goats with an inflammatory condition.

Effect of dose on the intravenous pharmacokinetics of tolfenamic acid in goats

The objective of this study was to determine the pharmacokinetics of tolfenamic acid (TA) following intravenous (IV) administration at doses of 2 and 4 mg/kg in goats. In this study, six healthy goats were used. TA was administered intravenously to each goat at 2 and 4 mg/kg doses in a cross-over pharmacokinetic design with a 15-day washout period. Plasma concentrations of TA were analyzed using the high performance liquid chromatography with ultraviolet detector, and pharmacokinetic parameters were assigned by noncompartmental analysis. Following IV administration at dose of 2 mg/kg, area under the concentration-time curve (AUC_0-∞ ), elimination half-life (t_1/2ʎz ), total clearance (Cl_T ) and volume of distribution at steady state (V_dss ) were 6.64 ± 0.81 hr^* µg/ml, 1.57 ± 0.14 hr, 0.30 ± 0.04 L h^-1  kg^-1 and 0.40 ± 0.05 L/kg, respectively. After the administration of TA at a dose of 4 mg/kg showed prolonged t_1/2ʎz , increased dose-normalized AUC_0-∞ , and decreased Cl_T . In goats, TA at 4 mg/kg dose can be administered wider dose intervals compared to the 2 mg/kg dose. However, further studies are needed to determine the effect of different doses on the clinical efficacy of TA in goats.

Effect of castration procedure on the pharmacokinetics of meloxicam in goat kids

The aim of this study was to determine the changes in the pharmacokinetics of meloxicam in goat kids who were castrated following the administration of xylazine. Six goat kids were used for the study. The study was performed in two periods according to a longitudinal study, with a 15-day washout period between periods. In the first period (Control group), 1 mg/kg meloxicam was administered by i.v. route to kids. In the second period (Castration group), the kids were sedated with 0.3 mg/kg xylazine and castration was performed following meloxicam administration. Plasma meloxicam concentration was analyzed using HPLC-UV, and pharmacokinetic parameters were calculated by noncompartmental model. In the control group following the administration of meloxicam, mean elimination half-life (t_{1/2 ʎz} ), area under the concentration-time curve (AUC_0-∞ ), total body clearance (Cl_T ), and volume of distribution at steady-state (V_dss ) were 13.50 ± 0.62 hr, 41.10 ± 2.86 hr µg/ml, 24.43 ± 1.75 ml hr^-1  kg^-1 , and 0.45 ± 0.03 L/kg, respectively. In the castration group, the t_{1/2 ʎz} of meloxicam prolonged, AUC_0-∞ increased, and Cl_T and V_dss decreased. In conclusion, the excretion of meloxicam from the body slowed and the t_{1/2 ʎz} was prolonged in the castrated goat kids following xylazine administration. However, there is a need to determine the pharmacodynamics of meloxicam in castrated goat kids.

Effect of benzylpenicillin on intravenous pharmacokinetics of acyclovir in red-eared slider turtles (Trachemys scripta elegans)

The aim of this study was to determine the effect of benzylpenicillin on the pharmacokinetics of acyclovir in red-eared slider turtles (Trachemys scripta elegans). Six clinically healthy red-eared slider turtles weighing 400 and 580 g were used for the study. Acyclovir (40 mg/kg) and benzylpenicillin (30 mg/kg) were administered intravenously to turtles. In the study, the cross-pharmacokinetic design (2 × 2) with a 30-day washout period was performed in two periods. Plasma concentrations of acyclovir were assayed using the high-performance liquid chromatography with fluorescence detection. Pharmacokinetic parameters were calculated by two-compartment open pharmacokinetic model. Following the administration of acyclovir alone, elimination half-life (t_{1/2 β} ), area under the plasma concentration-time curve (AUC), total clearance (Cl_T ), and volume of distribution at steady-state (V_dss ) were 20.12 hr, 1,372 hr * µg/mL, 0.03 L hr^-1  kg^-1 , and 0.84 L/kg, respectively. Benzylpenicillin administration increased t_{1/2 β} , AUC, and V_dss while decreased Cl_T of acyclovir. These results showed that benzylpenicillin changed the pharmacokinetics of acyclovir following simultaneous administration in turtles. However, further research is needed to determine molecular mechanism of interaction in turtle.

Effect of supportive therapy on the pharmacokinetics of intravenous marbofloxacin in endotoxemic sheep

The purpose of this study was to determine the influences of supportive therapy (ST) on the pharmacokinetics (PK) of marbofloxacin in lipopolysaccharide (LPS)-induced endotoxemic sheep. Furthermore, minimum inhibitory concentration (MIC) of marbofloxacin against Escherichia coli, Mannheimia haemolytica, Pasteurella multocida, Klebsiella pneumoniae, Salmonella spp., and Staphylococcus aureus was determined. The study was performed using a three-period cross PK design following a 15-day washout period. In the first period, marbofloxacin (10 mg/kg) was administered by an intravenous (IV) injection. In the second and third periods, marbofloxacin was co-administered with ST (lactated ringer + 5% dextrose + 0.45% sodium chloride, IV, 20 ml/kg, dexamethasone 0.5 mg/kg, SC) and ST + LPS (E. coli O55:B5, 10 µg/kg), respectively. Plasma marbofloxacin concentration was measured using HPLC-UV. Following IV administration of marbofloxacin alone, the t 1 / 2 λ z , AUC_0-∞ , Cl_T , and V_dss were 2.87 hr, 34.73 hr × µg/ml, 0.29 L hr^-1  kg^-1 , and 0.87 L/kg, respectively. While no change was found in the MBX + ST group in terms of the PK parameters of marbofloxacin, it was determined that the Cl_T of marbofloxacin decreased, AUC_0-∞ increased, and t 1 / 2 λ z and MRT prolonged in the MBX + ST + LPS group. MIC values of marbofloxacin were 0.031 to >16 µg/ml for E. coli, 0.016 to >16 µg/ml for M. haemolytica, 0.016-1 µg/ml for P. multocida, 0.016-0.25 µg/ml for K. pneumoniae, 0.031-0.063 µg/ml for Salmonella spp., and 0.031-1 µg/ml for S. aureus. The study results show the necessity to make a dose adjustment of marbofloxacin following concomitant administration of ST in endotoxemic sheep. Also, the PK and pharmacodynamic effect of marbofloxacin needs to be determined in naturally infected septicemic sheep following concomitant administration of single and ST.

Influences of tolfenamic acid and flunixin meglumine on the disposition kinetics of levofloxacin in sheep

The pharmacokinetics of levofloxacin (4 mg/kg), administered both alone and in combination with tolfenamic acid (2 mg/kg) and flunixin meglumine (2.2 mg/kg), was established after intravenous administration in sheep. Plasma levofloxacin concentrations were assayed by high-performance liquid chromatography and analysed according to the two-compartment open model. Following the administration of levofloxacin alone, the mean distribution half-life, elimination half-life, total clearance, volume of distribution at steady state and area under the plasma concentration-time curve were 0.20 h, 1.82 h, 0.39 L/h/kg, 0.96 L/kg and 10.40 h × µg/mL, respectively. Tolfenamic acid and flunixin meglumine caused a slow elimination and increased plasma concentrations of levofloxacin in combination administration. Levofloxacin, with an alteration in the dosage regimen, can be used effectively with tolfenamic acid and flunixin meglumine for the therapy of infections and inflammatory conditions in sheep.

Intravenous pharmacokinetics of moxifloxacin following simultaneous administration with flunixin meglumine or diclofenac in sheep

In this study, the pharmacokinetics of moxifloxacin (5 mg/kg) was determined following a single intravenous administration of moxifloxacin alone and co-administration with diclofenac (2.5 mg/kg) or flunixin meglumine (2.2 mg/kg) in sheep. Six healthy Akkaraman sheep (2 ± 0.3 years and 53.5 ± 5 kg of body weight) were used. A longitudinal design with a 15-day washout period was used in three periods. In the first period, moxifloxacin was administered by an intravenous (IV) injection. In the second and third periods, moxifloxacin was co-administered with IV administration of diclofenac and flunixin meglumine, respectively. The plasma concentration of moxifloxacin was assayed by high-performance liquid chromatography. The pharmacokinetic parameters were calculated using a two-compartment open pharmacokinetic model. Following IV administration of moxifloxacin alone, the mean elimination half-life (t_1/2β ), total body clearance (Cl_T ), volume of distribution at steady state (V_dss ) and area under the curve (AUC) of moxifloxacin were 2.27 hr, 0.56 L h^-1  kg^-1 , 1.66 L/kg and 8.91 hr*µg/ml, respectively. While diclofenac and flunixin meglumine significantly increased the t_1/2β and AUC of moxifloxacin, they significantly reduced the Cl_T and V_dss . These results suggest that anti-inflammatory drugs could increase the therapeutic efficacy of moxifloxacin by altering its pharmacokinetics.

Pharmacokinetics of pentoxifylline and its 5-hydroxyhexyl metabolite after intravenous administration of increasing doses to sheep

OBJECTIVE

To determine the pharmacokinetics of pentoxifylline (PTX) and its 5-hydroxyhexyl metabolite (M-I) after IV administration of increasing doses of PTX to sheep.

ANIMALS

6 healthy adult Merino sheep.

PROCEDURES

Each sheep received 10-, 20-, and 40-mg/kg doses of PTX, IV, with a 15-day washout period between doses. Blood samples were collected before and at predetermined times after administration of each dose to determine plasma PTX and M-I concentrations by high-performance liquid chromatography. Pharmacokinetic parameters for PTX and M-I were estimated by noncompartmental analysis.

RESULTS

No adverse effects were observed after administration of the 10- and 20-mg/kg doses. Following administration of the 40-mg/kg dose, all sheep developed tachycardia and hypersalivation and appeared agitated for approximately 4 hours. Plasma PTX concentrations considered therapeutic in other species were achieved in all sheep after administration of all 3 doses. Pharmacokinetic parameters for PTX and M-I varied in a dose-dependent linear manner. For PTX, the mean area under the concentration-time curve (AUC), elimination half-life, and volume of distribution increased with dose and ranged from 15.67 to 94.66 h·μg/mL, 0.68 to 0.91 hours, and 0.55 to 0.66 L/kg, respectively, whereas clearance decreased with dose and ranged from 0.42 to 0.64 L/h/kg. The mean ratio of the AUC for M-I to AUC for PTX ranged from 0.38 to 0.46.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that pharmacokinetic parameters for PTX and M-I varied in a dose-dependent linear manner in healthy sheep. Further studies are warranted to determine the therapeutic threshold and optimal dosage for PTX in sheep.

The effects of Mannheimia haemolytica and albendazole on marbofloxacin pharmacokinetics in lambs

The study aimed to define the effects of M. haemolytica and a single oral dose of albendazole on the single-dose pharmacokinetics of marbofloxacin in lambs. The pharmacokinetic-pharmacodynamic integration of marbofloxacin was applied to describe a 3 mg/kg intramuscular dose in lambs. The 6 healthy and 12 naturally infected with M. haemolytica lambs (Akkaraman, males weighing 10-15 kg and aged 2-3 months) were used in this study. In the marbofloxacin group, 6 healthy lambs received marbofloxacin. In the albendazole group after 2 weeks washout period, the same animals received marbofloxacin on 1 h after albendazole. In the diseased marbofloxacin group, 6 lambs naturally infected with M. haemolytica received marbofloxacin. In the diseased albendazole group, 6 lambs naturally infected with M. haemolytica received marbofloxacin on 1 h after albendazole. The marbofloxacin and albendazole were administered each as a single dose of 3 mg/kg intramuscular and 7.5 mg/kg oral, respectively, in the respective groups. Plasma concentration of marbofloxacin was measured with HPLC-UV and pharmacokinetic parameters were analyzed by non-compartmental model. Albendazole did not change the pharmacokinetic profiles of marbofloxacin in healthy and diseased lambs. However, M. haemolytica affected the pharmacokinetics of marbofloxacin in diseased lambs, AUC_0-24/MIC₉₀ ratio was not found to be higher than 125, but C_max/MIC₉₀ ratios was found to be higher than 10 for an MIC value of 0.25 μg/mL in all groups. The marbofloxacin dose described in this study may not be effective for the treatment of infections due to M. haemolytica in lambs, with MIC ≤ 0.25 μg/mL.

Pharmacokinetics and bioavailability of cefquinome and ceftriaxone in premature calves

The aim of this study was to evaluate the pharmacokinetics and bioavailability of cefquinome (CFQ) and ceftriaxone (CTX) following intravenous (IV) and intramuscular (IM) administrations in premature calves. Using a parallel design, 24 premature calves were randomly divided into the two antibiotic groups. Each of the six animals in the first group received CFQ (2 mg/kg) through IV or IM administration. The second group received CTX (20 mg/kg) via the same administration route. Plasma concentrations of the drugs were analyzed by high-performance liquid chromatography and noncompartmental methods. Mean pharmacokinetic parameters of CFQ and CTX following IV administration were as follows: elimination half-life (t_1/2λz ) 1.85 and 3.31 hr, area under the plasma concentration-time curve (AUC_0-∞ ) 15.74 and 174 hr * μg/ml, volume of distribution at steady-state 0.37 and 0.45 L/kg, and total body clearance 0.13 and 0.12 L hr^-1  kg^-1 , respectively. Mean pharmacokinetic parameters of CFQ and CTX after IM injection were as follows: peak concentration 4.56 and 25.04 μg/ml, time to reach peak concentration 1 and 1.5 hr, t_1/2λz 4.74 and 3.62 hr, and AUC_0-∞ 22.75 and 147 hr * μg/ml, respectively. The bioavailability of CFQ and CTX after IM injection was 141% and 79%, respectively. IM administration of CFQ (2 mg/kg) and CTX (20 mg/kg) can be recommended at 12-hr interval for treating infections caused by susceptible bacteria, with minimum inhibitory concentration values of ≤0.5 and ≤4 μg/ml, respectively, in premature calves. However, further research is indicated to assess the pharmacokinetic parameters following multiple doses of the drug in premature calves.

Pharmacokinetics of enrofloxacin and danofloxacin in premature calves

The aim of this study was to determine the pharmacokinetics/pharmacodynamics of enrofloxacin (ENR) and danofloxacin (DNX) following intravenous (IV) and intramuscular (IM) administrations in premature calves. The study was performed on twenty-four calves that were determined to be premature by anamnesis and general clinical examination. Premature calves were randomly divided into four groups (six premature calves/group) according to a parallel pharmacokinetic (PK) design as follows: ENR-IV (10 mg/kg, IV), ENR-IM (10 mg/kg, IM), DNX-IV (8 mg/kg, IV), and DNX-IM (8 mg/kg, IM). Plasma samples were collected for the determination of tested drugs by high-pressure liquid chromatography with UV detector and analyzed by noncompartmental methods. Mean PK parameters of ENR and DNX following IV administration were as follows: elimination half-life (t_1/2λz ) 11.16 and 17.47 hr, area under the plasma concentration-time curve (AUC_0-48 ) 139.75 and 38.90 hr*µg/ml, and volume of distribution at steady-state 1.06 and 4.45 L/kg, respectively. Total body clearance of ENR and DNX was 0.07 and 0.18 L hr^-1  kg^-1 , respectively. The PK parameters of ENR and DNX following IM injection were t_1/2λz 21.10 and 28.41 hr, AUC_0-48 164.34 and 48.32 hr*µg/ml, respectively. The bioavailability (F) of ENR and DNX was determined to be 118% and 124%, respectively. The mean AUC_0-48CPR /AUC_0-48ENR ratio was 0.20 and 0.16 after IV and IM administration, respectively, in premature calves. The results showed that ENR (10 mg/kg) and DNX (8 mg/kg) following IV and IM administration produced sufficient plasma concentration for AUC_0-24 /minimum inhibitory concentration (MIC) and maximum concentration (C_max )/MIC ratios for susceptible bacteria, with the MIC₉₀ of 0.5 and 0.03 μg/ml, respectively. These findings may be helpful in planning the dosage regimen for ENR and DNX, but there is a need for further study in naturally infected premature calves.

Pharmacokinetics of tolfenamic acid in red-eared slider turtles (Trachemys scripta elegans)

OBJECTIVE

To determine the pharmacokinetics of tolfenamic acid (TA) after different routes of administration [intravenous (IV) and intramuscular (IM), 2 mg kg^-1] and doses (IV, 2 and 4 mg kg^-1) in red-eared slider turtles (Trachemys scripta elegans).

STUDY DESIGN

Randomized experimental trial.

ANIMALS

Sixteen healthy red-eared slider turtles.

METHODS

Turtles were randomly assigned to two groups (n = 8 each). Group 1 received TA at a dose of 2 mg kg^-1 IV and then IM, after a washout period of 30 days. Group 2 received 4 mg kg^-1 TA IV. A noncompartmental analysis was used to calculate pharmacokinetic variables.

RESULTS

No local and/or systemic adverse drug effects were observed in any turtle. Elimination half-life and mean residence time following IM administration at 2 mg kg^-1 were significantly longer than those following IV administration. The bioavailability following IM administration was complete. The area under the plasma concentration-time curve, elimination half-life, mean residence time and total clearance were significantly different between the dose groups.

CONCLUSIONS AND CLINICAL RELEVANCE

The absence of adverse reactions in the turtles of the study of TA along with the favourable pharmacokinetic properties (the long half-life and the complete bioavailability) of TA administered at the single doses of 2 and 4 mg kg^-1 suggest the possibility of its effective use in turtles. However, further studies are required to establish a multiple dosage regimen of TA and to evaluate the clinical efficacy of administering TA.

Pharmacokinetics of levamisole in the red-eared slider turtles (Trachemys scripta elegans)

The pharmacokinetics and bioavailability of levamisole were determined in red-eared slider turtles after single intravenous (IV), intramuscular (IM), and subcutaneous (SC) administration. Nine turtles received levamisole (10 mg/kg) by each route in a three-way crossover design with a washout period of 30 days. Blood samples were collected at time 0 (pretreatment), and at 0.25, 0.5, 1, 1.5, 3, 6, 9, 12, 18, 24, 36, and 48 hr after drug administration. Plasma levamisole concentrations were determined by a high-performance liquid chromatography assay. Data were analyzed by noncompartmental methods. The mean elimination half-life was 5.00, 7.88, and 9.43 hr for IV, IM, and SC routes, respectively. The total clearance and volume of distribution at steady state for the IV route were 0.14 L hr^-1  kg^-1 and 0.81 L/kg, respectively. For the IM and SC routes, the peak plasma concentration was 9.63 and 10.51 μg/ml, respectively, with 0.5 hr of T_max . The bioavailability was 93.03 and 115.25% for the IM and SC routes, respectively. The IM and SC route of levamisole, which showed the high bioavailability and long t_1/2ʎz , can be recommended as an effective way for treating nematodes in turtles.

Pharmacokinetics of intravenous and intramuscular danofloxacin in red-eared slider turtles (Trachemys scripta elegans)

This study aimed to investigate the pharmacokinetics of danofloxacin in red-eared slider turtle (Trachemys scripta elegans) following a single intravenous (IV) and intramuscular (IM) administrations of 6 mg/kg, using a two-way crossover study with 30-day washout period. Eight clinically healthy red-eared slider turtle weighing 410-600 g (mean 490 g) were used for the study. Danofloxacin concentrations were measured using the reversed-phase high-performance liquid chromatography. The plasma concentration-time data were evaluated by a non-compartmental method. After IV administration, the elimination half-life (t_1/2ʎz), mean residence time (MRT_0-∞), area under the concentration-time curve (AUC_0-∞), volume of distribution at steady state and total body clearance in plasma were 24.17 hr, 30.64 hr, 143.31 hr·µg/ml, 1.29 l/kg and 0.04 l/hr/kg, respectively. Following IM administration, t_1/2ʎz, MRT_0-∞, AUC_0-∞, peak concentration (C_max), time to reach C_max, and bioavailability in plasma were 32.00 hr, 41.15 hr, 198.23 hr·µg/ml, 8.75 µg/ml, 1.5 hr and 139.89%, respectively. Danofloxacin has clinically superior pharmacokinetic properties, including the complete IM absorption, slow elimination and wide volume of distribution in red-eared slider turtles. However, further pharmacokinetics/pharmacodynamics studies are necessary for the treatment of diseases caused by susceptible bacteria with known minimum inhibitory concentration values in red-eared slider turtles.

Changes in novel gastrointestinal and renal injury markers in the blood plasma of sheep following increasing intravenous doses of tolfenamic acid

The administration of high doses of non-steroidal anti-inflammatory drugs (NSAID), such as tolfenamic acid (TA), has undesirable effects on different organs. Some novel biomarkers have been reported that can determine the gastrointestinal and renal injury caused by a high dose of NSAIDs or other toxic substances. This study was aimed at determining the changes in gastrointestinal (TFF2 and HYP), renal (NGAL and KIM-1) and cardiac (cTn-I, CK-MB) injury markers after the use of increasing intravenous doses of TA in sheep. TA was administered intravenously to groups of six sheep each, at the dose levels of 0 (Group 0, i.e., G0), 2 (G2), 4 (G4), 8 (G8) and 16 (G16) mg/kg. The concentrations of the studied biomarkers were measured at 3, 9, 18 and 36 h after administration of TA. The TFF2 and NGAL concentrations in G16 were found to be significantly higher (P < 0.05) than in the other groups except for G8 at different sampling times. HYP concentration in G16 was observed to be significantly (P < 0.05) lower than that in all other groups at 36 h. KIM-1 level in G16 was significantly (P < 0.05) higher than in all other groups at different sampling times. An increase in the renal markers, KIM-1 and NGAL, in G8 was observed before any change in plasma creatinine and urea. The cardiac marker cTn-I in G16 was significantly (P < 0.05) higher than in other groups at different sampling times. The results showed that the novel biomarkers (HYP, TFF2, NGAL, and KIM-1) can be used to determine gastric and renal injury in sheep.

Pharmacokinetics of cefquinome after single and repeated subcutaneous administrations in sheep

The purpose of this study was to determine the pharmacokinetics of cefquinome (CFQ) following single and repeated subcutaneous (SC) administrations in sheep. Six clinically healthy, 1.5 ± 0.2 years sheep were used for the study. In pharmacokinetic study, the crossover design in three periods was performed. The withdrawal interval between the study periods was 15 days. In first period, CFQ (Cobactan, 2.5%) was administered by an intravenous (IV) bolus (3 sheep) and SC (3 sheep) injections at 2.5 mg/kg dose. In second period, the treatment administration was repeated via the opposite administration route. In third period, CFQ was administrated subcutaneously to each sheep (n = 6) at a dose of 2.5 mg/kg q. 24 hr for 5 days. Plasma concentrations of CFQ were measured using the HPLC-UV method. Pharmacokinetic parameters were calculated using non-compartmental methods. The elimination half-life and mean residence time of CFQ after the single SC administration were longer than IV administration (p < 0.05). Bioavailability (F%) of CFQ following the single SC administration was 123.51 ± 11.54%. The area under the curve (AUC_0-∞ ) and peak concentration following repeated doses (last dose) were higher than those observed after the first dose (p < 0.05). CFQ accumulated after repeated SC doses. CFQ can be given via SC at a dose of 2.5 mg/kg every 24 hr for the treatment of infections caused by susceptible pathogens, which minimum inhibitory concentration is ≤1.0 μg/ml in sheep.