Disposition kinetics and dosage regimen of levofloxacin on concomitant administration with paracetamol in crossbred calves

The disposition kinetics of levofloxacin was investigated in six male crossbred calves following single intravenous administration, at a dose of 4 mg/kg body weight, into the jugular vein subsequent to a single intramuscular injection of paracetamol (50 mg/kg). At 1 min after the injection of levofloxacin, the concentration of levofloxacin in plasma was 17.2 ± 0.36 µg/ml, which rapidly declined to 6.39 ± 0.16 µg/ml at 10 min. The drug level above the MIC₉₀ in plasma, was detected for up to 10 h. Levofloxacin was rapidly distributed from blood to the tissue compartment as evidenced by the high values of the distribution coefficient, α (17.3 ± 1.65 /h) and the ratio of K₁₂/K₂₁ (1.83 ± 0.12). The values of AUC and Vd_area were 12.7 ± 0.12 µg.h/ml and 0.63 ± 0.01 l/kg. The high ratio of the AUC/MIC (126.9 ± 1.18) obtained in this study indicated the excellent antibacterial activity of levofloxacin in calves. The elimination half-life, MRT and total body clearance were 1.38 ± 0.01 h, 1.88 ± 0.01 h and 0.32 ± 0.003 l/kg/h, respectively. Based on the pharmacokinetic parameters, an appropriate intravenous dosage regimen for levofloxacin would be 5 mg/kg repeated at 24 h intervals when prescribed with paracetamol in calves.     

Subcutaneous pharmacokinetics and dosage regimen of cefotaxime in buffalo calves (Bubalus bubalis)

The pharmacokinetics and dosage regimen of cefotaxime following its single subcutaneous administration (10 mg/kg) were investigated in buffalo calves. Plasma and urine samples were collected over 10 and 24 h post administration, respectively. Cefotaxime in plasma and urine was estimated by microbiological assay technique using E. coli as test organism. The pharmacokinetic profiles fitted one-compartment open model. The peak plasma levels of cefotaxime were 6.48 ± 0.52 µg/ml at 30 min and the drug was detected upto 10 h. The absorption half-life and elimination half-life were 0.173 ± 0.033 h and 1.77 ± 0.02 h, respectively. The apparent volume of distribution and total body clearance were 1.17 ± 0.10 l/kg and 0.45 ± 0.03 l/kg/h, respectively. The urinary excretion of cefotaxime in 24 h, was 5.36 ± 1.19 percent of total administrated dose. A satisfactory subcutaneous dosage regimen for cefotaxime in buffalo calves would be 13 mg/kg repeated at 12 h intervals.     

Pharmacokinetics, urinary excretion and dosage regimen of levofloxacin following a single intramuscular administration in cross bred calves

The pharmacokinetics and urinary excretion following single intramuscular administration of levofloxacin at a dose of 4 mg/kg was investigated in seven male cross bred calves. Appreciable plasma concentration of levofloxacin (0.38 ± 0.06 µg/ml) was detected at 1 min after injection and the peak plasma level of 3.07 ± 0.08 µg/ml was observed at 1 h. The drug level above MIC₉₀ in plasma was detected up to 12 h after administration. Rapid absorption of the drug was also evident by the high value of the absorption rate constant (2.14 ± 0.24 /h). The overall systemic bioavailability of levofloxacin, after intramuscular administration, was 56.6 ± 12.4%. The high value of AUC (7.66 ± 0.72 mg . h/ml) reflected the vast area of body covered by drug concentration. Extensive distribution of the drug into various body fluids and tissues was noted by the high value of Vd_area (1.02 ± 0.05 l/kg). The high ratio of AUC/MIC (76.6 ± 7.25) obtained in this study indicated excellent clinical and bacteriological efficacy of levofloxacin in calves. The elimination half-life and MRT were 3.67 ± 0.4 h and 5.57 ± 0.51 h, respectively. The total body clearance (Cl_B) was 204.9 ± 22.6 ml/kg/h. On the basis of the pharmacokinetic parameters, a suitable intramuscular dosage regimen for levofloxacin in calves would be 1.5 mg/kg repeated at 12 h intervals.     

Plasma Concentrations,Pharmacokinetics and Urinary Excretion of Gatifloxacin after Single Intravenous Injection in Buffalo Calves

The pharmacokinetics and urinary excretion of gatifloxacin were investigated after a single intravenous injection of 4 mg/kg body weight in buffalo calves. The therapeutic plasma drug concentration was maintained for up to 12 h. Gatifloxacin rapidly distributed from blood to tissue compartments, which was evident from the high values of the distribution rate constant, α₁ (11.1 ± 1.06 h⁻¹) and the rate constant of transfer of drug from central to peripheral compartment, k ₁₂ (6.29 ± 0.46 h⁻¹). The area under the plasma drug concentration–time curve and apparent volume of distribution were 17.1 ± 0.63 (μg.h)/ml and 3.56 ± 0.95 L/kg, respectively. The elimination half-life (t _{1/2 β}), total body clearance (Cl_B) and the ratio of drug present in tissues and plasma (T/P) were 10.4 ± 2.47 h, 235.1 ± 8.47 ml/(kg.h) and 10.1 ± 2.25, respectively. About 19.7% of the administered drug was excreted in urine within 24 h. A satisfactory intravenous dosage regimen for gatifloxacin in buffalo calves would be 5.3 mg/kg at 24 h intervals. Abbreviations for pharmacokinetic parameters are given in the footnote of Table I     

Pharmacokinetics and Dosage Regimen of Ceftriaxone in Buffalo Calves

The pharmacokinetics and dosage regimen of ceftriaxone were investigated in buffalo calves (n = 6) following a single intravenous administration of ceftriaxone (10 mg/kg). The elimination rate constant was 0.18 +/- 0.01 h(-1) and the elimination half-life was 3.79 +/- 0.09 h. The apparent volume of distribution (Vd(area)) was 1.40 +/- 0.01 L/kg and the total plasma clearance was 0.26 +/- 0.01 L/(kg h). Approximately 43% of total administered dose of ceftriaxone was excreted in urine within 8 h. To maintain a minimum therapeutic concentration of 1 microg/ml, a satisfactory intravenous dosage regimen of ceftriaxone in buffalo calves is 13 mg/kg repeated at 12 h intervals.     

Clinical pharmacokinetics of norfloxacin-glycine acetate after intravenous and oral administration in pigs

The pharmacokinetics and dosage regimen of norfloxacin-glycine acetate (NFLXGA) was investigated in pigs after a single intravenous (i.v.) or oral (p.o.) administration at a dosage of 7.2 mg/kg body weight. After both i.v. and p.o. administration, plasma drug concentrations were best fitted to an open two-compartment model with a rapid distribution phase. After i.v. administration of NFLXGA, the distribution (t_1/2α) and elimination half-life (t_1/2β) were 0.36 ± 0.07 h and 7.42 ± 3.55 h, respectively. The volume of distribution of NFLXGA at steady state (Vd_ss) was 4.66 ± 1.39 l/kg. After p.o. administration of NFLXGA, the maximal absorption concentration (C_max) was 0.43 ± 0.06 µg/ml at 1.36 ± 0.39 h (T_max). The mean absorption (t_1/2ka) and elimination half-life (t_1/2β) of NFLXGA were 0.78 ± 0.27 h and 7.13 ± 1.41 h, respectively. The mean systemic bioavailability (F) after p.o. administration was 31.10 ± 15.16%. We suggest that the optimal dosage calculated from the pharmacokinetic parameters is 5.01 mg/kg per day i.v. or 16.12 mg/kg per day p.o.     

The kinetic disposition and dosage regimen for carbenicillin in buffalo calves

The distribution half-life, elimination half-life, apparent volume of distribution and total body clearance of carbenicillin in healthy buffalo calves following a single intravenous administration (50 mg/kg) were 0.057±0.005 h, 1.688±0.11 h, 0.185±0.021 L kg^-1 and 75.97±6.519 ml kg^-1 h^-1 respectively. A satisfactory dosage regimen for carbenicillin in buffalo calves was calculated to be 56 mg/kg followed by 52 mg/kg body weight repeated at 6 h intervals.     

Disposition kinetics,urinary excretion and dosage regimen of kanamycin in buffalo calves following single intravenous administration

The disposition kinetics and appropriate dosage regimen for kanamycin were investigated in buffalo calves following a single intravenous dose of 10 mg/kg body weight. The distribution and elimination half-lives were 0.12±0.01 h and 1.94±0.11 h, respectively. The apparent volume of distribution and total body clearance were 0.2±0.01 L/kg and 92.9±3.69 ml/kg/h, respectively. About 74% of the administered dose was excreted in urine in 24 h. A suitable dosage regimen for the intravenous administration of kanamycin was also calculated.Abbreviation SEM standard error of the mean     

The Disposition Kinetics,Urinary Excretion and Dosage Regimen of Ciprofloxacin in Buffalo Calves (Bubalus bubalis)

The disposition kinetics, urinary excretion and a dosage regimen for ciprofloxacin after a single intravenous administration of 5 mg/kg was investigated in 5 healthy buffalo calves. The disposition kinetics were best fitted to a three-compartment open model. After 1 min, the concentration of ciprofloxacin in plasma was 8.50±0.39 g/ml and the minimum therapeutic concentration was maintained for 10 h. The elimination half-life and volume of distribution were 3.88 and 0.08 h and 3.97±0.22 L/kg, respectively. The total body clearance and T/P ratio were 0.709±0.025 L/kg per h and 6.13±0.54, respectively. Approximately 28.3% of the total administered dose of ciprofloxacin was recovered in urine within 24 h of administration. To maintain a minimum therapeutic plasma concentration of 0.10 g/ml, a satisfactory intravenous dosage regimen of ciprofloxacin, computed on the basis of disposition kinetic data obtained in healthy buffalo calves, would be 3 mg/kg repeated at 12 h intervals.     

Disposition Kinetics and Urinary Excretion of Pefloxacin after Intravenous Injection in Crossbred Calves

The disposition kinetics and urinary excretion of pefloxacin after a single intravenous administration of 5 mg/kg were investigated in crossbred calves and an appropriate dosage regimen was calculated. At 1 min after injection, the concentration of pefloxacin in the plasma was 18.95±0.892 g/ml, which declined to 0.13±0.02 g/ml at 10 h. The pefloxacin was rapidly distributed from the blood to the tissue compartment as shown by the high values for the initial distribution coefficient, (12.1±1.21 h^–1) and the constant for the rate of transfer of drug from the central to the peripheral compartment, K ₁₂ (8.49±0.99 h^–1). The elimination half-life and volume of distribution were 2.21±0.111 h and 1.44±0.084 L/kg, respectively. The total body clearance (Cl_B) and the ratio of the drug present in the peripheral to that in the central compartment (P/C ratio) were 0.454±0.026 L/kg h) and 5.52±0.519, respectively. On the basis of the pharmacokinetic parameters obtained in the present study, an appropriate intravenous dosage regimen for pefloxacin in cattle for most of the bacteria sensitive to it would be 6.4 mg/kg repeated at 12 h intervals.     

Modification of the Pharmacokinetics and Dosage of Cefuroxime by Endotoxin-induced Fever in Buffalo Calves

The effect of endotoxin-induced fever on the pharmacokinetics and dosage regimen of cefuroxime was investigated in buffalo calves following a single intravenous dose of 10 mg/kg body weight. The fever was induced by intravenous administration of E. coli endotoxin at a dose of 1 g/kg body weight. The distribution and elimination half-lives were 0.100 h and 1.82 h, respectively, in healthy and 0.109 h and 2.28 h, respectively, in febrile buffalo calves. About 91% of the administered dose was excreted in the urine within 24 h. There was no effect of fever on the plasma protein binding of cefuroxime. The dosage regimen for intravenous administration of cefuroxime may be reduced in febrile conditions but the probability of this was only 0.3.     

Disposition kinetics and dosage regimen of sulfapyridine in buffalo (Bubalus bubalis).

The disposition kinetics and dosage regimen of sulfapyridine were studied in buffalo calves following a single intravenous dose of 100 mg/kg. Distribution half-life (t1/2 alpha) elimination half-life (t1/2 beta) and Vd (area) was 0.181 +/- 0.008 h, 13.4 +/- 0.52 h and 0.59 +/- 0.03 L kg-1, respectively. Total body clearance, which represents the sum of all clearance processes, and tissue/plasma (T/P) ratio were calculated to be 31.1 +/- 2.28 ml kg-1 h-1 and 2.25 +/- 0.09, respectively. A satisfactory intravenous dosage regimen of sulfapyridine in buffalo would be 104 mg/kg followed by 75 mg/kg at 24 h intervals.     

The disposition kinetics,urinary excretion and dosage regimen of amikacin in cross-bred bovine calves

The disposition kinetics, urinary excretion and dosage regimen of amikacin after a single intravenous administration of 10 mg/kg was investigated in six cross-bred bovine calves. At 1 min, the concentration of amikacin in the plasma was 116.9±3.16 µg/ml and the minimum therapeutic concentration was maintained for 8 h. The elimination half-life and volume of distribution were 3.09±0.27 h and 0.4±0.03 L/kg, respectively. The total body clearance (Cl_B) and T/P ratio were 0.09±0.002 L/kg/h and 4.98±0.41, respectively. Approximately 50% of the total dose of amikacin was recovered in the urine within 24 h after administration. Amikacin in concentrations ranging from 5 to 150 µg/ml bound to plasma proteins to the extent of 6.32%±0.42%. A satisfactory intravenous dosage regimen of amikacin in bovine calves would be 13 mg/kg followed by 12 mg/kg at 12 h intervals.     

Disposition kinetics and urinary excretion of ciprofloxacin in goats following single intravenous administration

We evaluated the pharmacokinetics of ciprofloxacin in serum (n = 6) and urine (n = 4) in goats following a single intravenous administration of 4 mg/kg body weight. The serum concentration-time curves of ciprofloxacin were best fitted by a two-compartment open model. The drug was detected in goat serum up to 12 h. The elimination rate constant (β) and elimination half-life (t_1/2β) were 0.446 ± 0.04 h^-1 and 1.630 ± 0.17 h, respectively. The apparent volume of distribution at steady state (Vd_ss) was 2.012 ± 0.37 l/kg and the total body clearance (Cl_B) was 16.27 ± 1.87 ml/min/kg. Urinary recovery of ciprofloxacin was 29.70% ± 10.34% of the administered dose within 36 h post administration. In vitro serum protein binding was 41% ± 13.10%. Thus, a single daily intravenous dose of 4 mg/kg is sufficient to maintain effective levels in serum and for 36 h in urine, allowing treatment of systemic, Gram-negative bacterial infections and urinary tract infections by most pathogens.     

Pharmacokinetics and bioavailability of doxycycline in ostriches (Struthio camelus) at two different dose rates

A bioavailability and pharmacokinetics study of doxycycline was carried out on 30 healthy ostriches after a single intravenous (IV), intramuscular (IM) and oral dose of 15 mg/kg body weight. The plasma doxycycline concentration was determined by HPLC/UV at 0 (pretreatment), 0.08, 0.25, 0.5 1, 2, 4, 6, 8, 12, 24 and 48 h after administration. The plasma concentration-time curves were examined using non-compartmental methods based on the statistical moment theory for only the higher dose. After IV administration, the elimination half-life (t_1/2β), mean residence time (MRT), volume of distribution at the steady-state (V_ss), volume of distribution (Vd_area) and total body clearance (Cl_B) were 7.67 ± 0.62 h, 6.68 ± 0.86 h, 0.86 ± 0.16 l/kg, 1.67 ± 0.52 l/kg and 2.51 ± 0.63 ml/min/kg, respectively. After IM and oral dosing, the mean peak plasma concentrations (C_max) were 1.34 ± 0.33 and 0.30 ± 0.04 µg/ml, respectively, which were achieved at a post-administration time (t_max) of 0.75 ± 0.18, 3.03 ± 0.48 h, respectively. The t_1/2β, Vd_area and Cl_B after IM administration were 25.02 ± 3.98 h, 23.99 ± 3.4 l/kg and 12.14 ± 1.71 ml/min/kg, respectively and 19.25 ± 2.53 h, 61.49 ± 7 l/kg and 40.19 ± 3.79 ml/min/kg after oral administration, respectively. The absolute bioavailability (F) of doxycycline was 5.03 and 17.52% after oral and IM administration, respectively. These results show that the dose data from other animals particularly mammals cannot be extrapolated to ostriches. Therefore, based on these results along with those reported in the literature, further studies on the pharmacokinetic/pharmacodynamic, in vitro minimum inhibitory concentration values and clinical applications of doxycycline in ostriches are required.     

Pharmacokinetics,urinary excretion and plasma protein binding of danofloxacin following intravenous administration in buffalo calves (Bubalus bubalis)

Pharmacokinetics, urinary excretion and plasma protein binding of danofloxacin was investigated in buffalo calves following intravenous administration at the dose rate of 1.25 mg/kg to select the optimal dosage regimen of danofloxacin. Drug concentrations in plasma and urine were measured by microbiological assaying. In vitro plasma protein binding was determined employing the equilibrium dialysis technique. The distribution and elimination of danofloxacin were rapid, as indicated by values (mean ±SD) of distribution half-life (t_1/2α = 0.16 ± 0.07 h) and elimination half-life (t_1/2β = 4.24 ± 1.78 h), respectively. Volume of distribution at steady state (Vss) = 3.98 ± 1.69 L/kg indicated large distribution of drug. The area under plasma drug concentration versus time curve (AUC) was 1.79 ± 0.28 μg/mlxh and MRT was 8.64 ± 0.61 h. Urinary excretion of danofloxacin was 23% within 48 h of its administration. Mean plasma protein binding was 36% at concentrations ranging from 0.0125 μg/ml to 1 μg/ml. On the basis of pharmacokinetic parameters obtained, it is concluded that the revision of danofloxacin dosage regimen in buffalo calves is needed because the current dosage schedule (1.25 mg/kg) is likely to promote resistance.     

Pharmacokinetics and urinary excretion of sulphadimidine in buffalo calves

Pharmacokinetics and urinary excretion of sulphadimidine (SDI) were determined in buffalo calves following single oral administration (150 mg/kg). The plasma levels of free sulphadimidine were above minimum effective therapeutic concentration (> 40 micrograms/ml) between 4 and 12 h and the N4-acetylated form of the drug was in the range of 7.2-19.3%. Kinetic evaluation of plasma levels was performed using a two-compartment open model. The absorption and elimination half-lives of SDI were 3.01 and 11.94 h, respectively. Based on this study, an optimal dosage regimen of sulphadimidine in buffalo calves would be 100 mg/kg, followed by 50 mg/kg at 12 h intervals. Sulphadimidine was mainly excreted in the urine as free amine. The percentage of N4-acetyl sulphadimidine in urine was comparatively higher than in plasma.     

Pharmacokinetics and Dosage Regimen of Enrofloxacin in Buffalo Bulls after Intramuscular Administration

The disposition kinetics and dosage regimen of enrofloxacin were investigated in breeding buffalo bulls following a single intramuscular administration of 5 mg/kg. The absorption half-life, half-life of the terminal phase, apparent volume of distribution and total body clearance were 0.262±0.099 h, 1.97±0.23 h, 0.61±0.13 L/kg and 210.2±18.6 ml/(kg.h), respectively. Therapeutic plasma levels (1 g/ml) were maintained for up to 6 h. A satisfactory intramuscular dosage regimen for enrofloxacin in buffalo bulls would be 8.5 mg/kg followed by 8.0 mg/kg at 8 h intervals.     

A hematologic and blood chemical study of Swedish purchased calves.

The hemoglobin (Hb), packed cell volume (PCV), erythrocytes (R.G.), serum iron (SI) and unsaturated iron binding capacity (UIBG) were examined in a total of 386 purchased calves for the duration of 1 year. The calves were tested within 3 days of arrival at the buyer’s herd. The average age of the calves was 28 ± 10 days ().The results may be summarized as follows:

1. Approx. 35% of the calves had Hb values ≦ 10.0 g/100 ml.
2. Fifteen% of the calves had ≦ 6.0 × 10⁶ R.C. per µl.
3. Fifty-three calves or about 14% showed SI values ≦ 40 µg/100 ml and 131 calves or 34% ≦ 80 µg/100 ml.
4. Twenty-seven % of the calves had UIBG values > 501 µg/100 ml.
5. Almost half the calves (48%) had a saturation percentage of transferrin with iron below 20% and 138 calves (36%) below 15%.

These figures among others in the study indicate that 13–35% of the purchased calves suffered from iron deficiency anemia.     

Disposition and dosage regimen of cephaloridine in calves

The disposition and dosage regimen of cephaloridine were investigated in healthy calves following a single intramuscular administration of 10 mg/kg. The absorption halflife, climination halflife, apparent volume of distribution and total body clearance were 0.107±0.025 h, 2.08±0.14 h, 0.70±0.07L kg^-1 and 235.8±21.9 ml kg^-1 h^-1, respectively. Therapeutic plasma levels (1 g/ml) were maintained for up to 7 h. A satisfactory intramuscular dosage regimen for cephaloridine in calves would be 10 mg/kg repeated at 8 h intervals.