Disposition kinetics, bioavailability and renal clearance of cefepime in calves

Modelling concentrations of antimicrobial drugs: comparative pharmacokinetics of cephalosporin antimicrobials and accuracy of allometric scaling in food-producing and companion animals

Background

To optimize antimicrobial dosing in different animal species, pharmacokinetic information is necessary. Due to the plethora of cephalosporin antimicrobials and animal species in which they are used, assessment of pharmacokinetics in all species is unfeasible. In this study we aimed to describe pharmacokinetic data of cephalosporins by reviewing the available literature for food producing and companion animal species. We assessed the accuracy of interspecies extrapolation using allometric scaling techniques to determine pharmacokinetic characteristics of cephalosporins in animal species for which literature data is unavailable. We assessed the accuracy of allometric scaling by comparing the predicted and the published pharmacokinetic value in an animal species/humans not included in the allometric modelling.

Results

In general, excretion of cephalosporins takes place mainly through renal mechanisms in the unchanged form and volume of distribution is limited in all animal species. Differences in plasma protein binding capacity and elimination half-life are observed but available information was limited. Using allometric scaling, correlations between body weight (BW) and volume of distribution (Vd) and clearance (Cl) were R² > 0.97 and R² > 0.95 respectively for ceftazidime, ceftiofur, cefquinome and cefepime but not ceftriaxone. The allometric exponent ranged from 0.80 to 1.31 for Vd and 0.83 to 1.24 for Cl. Correlations on half-life ranged from R² 0.07–0.655 (literature) and R² 0.102–0.876 (calculated).

Conclusions

Allometric scaling can be applied for interspecies extrapolation of cephalosporin pharmacokinetic parameters Vd and Cl, but not elimination half-life. We hypothesize that the accuracy could be improved by using more refined scaling techniques.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0817-2) contains supplementary material, which is available to authorized users.

Influence of flunixin on the disposition kinetic of cefepime in goats

The pharmacokinetic profile of cefepime (10 mg/kg b.w.) was studied following intravenous and intramuscular administration of cefepime alone and coadministered with flunixin (2.2 mg/kg b.w.) in goats. Cefepime concentrations in serum were determined by microbiological assay technique using Escherichia coli (MTCC 443) as test organism. Following intravenous injection of cefepime alone and in combination with flunixin, there are no significant changes in the pharmacokinetic parameters. Following intramuscular injection of cefepime alone and in combination with flunixin, the maximum serum concentration was significantly increased in flunixin coadministered group compared with cefepime alone. However, no significant changes were reported in other pharmacokinetic parameters. The result of in vitro protein binding study indicated that 15.62% of cefepime was bound to goat's serum protein. The mean bioavailability was 92.66% and 95.27% in cefepime alone and coadministered with flunixin, respectively. The results generated from the present study suggest that cefepime may be coadministered with flunixin without change in dose regimen. Cefepime may be given intramuscularly at 12 h intervals to combat susceptible bacterial infections.

Influence of E. coli lipopolysaccharide induced fever on the plasma kinetics of cefepime in cross-bred calves

The pharmacokinetic behavior of cefepime was studied in healthy and febrile cross-bred calves after single intravenous administration (10 mg/kg). The fever was induced with E. coli lipopolysaccharide (1 microg/kg, IV). The drug concentration in plasma was detected by microbiological assay method using E. coli (MTCC 739) test organism. Pharmacokinetic analysis of disposition data indicated that intravenous administration data were best described by 2 compartment open model. At 1 min the concentration of cefepime in healthy and febrile animals were 55.3 +/- 0.54 microg/ml and 50.0 +/- 0.48 microg/ml, respectively and drug was detected up to 12 h. The elimination half-life of cefepime was increased from 1.26 +/- 0.01 h in healthy animals to 1.62 +/- 0.09 h in febrile animals. Drug distribution was altered by fever as febrile animals showed volume of distribution (0.27 +/- 0.02 L/kg) higher than normal animal (0.19 +/- 0.01 L/kg). Total body clearances in healthy and febrile animals were 104.4 +/- 2.70 and 114.2 +/- 1.20 ml/kg/h, respectively. To maintain minimum therapeutic concentration of 1 mug/ml, a satisfactory dosage regimen of cefepime in healthy and febrile cross-bred calves would be 15.5 mg/kg and 8.2 mg/kg body weight, respectively, to be repeated at 8 h intervals. The T>MIC values (8 h) of cefepime suggested that this agent is clinically effective in the treatment of various infections.

Acute-phase response alters the disposition kinetics of cefepime following intravenous administration to rabbits

The effect of experimentally induced fever on the pharmacokinetics of cefepime administered intravenously at a dose of 75 mg/kg bw was studied in six healthy rabbits. The study was conducted in two consecutive phases, separated by a washout period of 2 weeks. Infection was induced by the intravenous inoculation of 5 x 10(8) cfu of Escherichia coli 24 h before the pharmacokinetic investigation was carried out. Serial blood samples for cefepime concentration determination were obtained for 48 h following drug administration. The concentrations of cefepime in the plasma were determined by a quantitative microbiological assay using an agar-gel diffusion method employing Bacillus subtilis ATCC 6633 as the test organism, with a level of detectability of approximately 0.10 microg/ml. Cefepime plasma concentrations versus time were evaluated by non-compartmental methods using WinNonLin. Cefepime was well tolerated and no serious adverse events were observed. Rectal temperature increased 1 degree C 24 h post injection in infected animals. Highly significant differences in the blood plasma concentrations of cefepime were observed between febrile and healthy animals at all the sampling times. This could explain the greater area under the plasma level-time curve of the drug in febrile compared with healthy animals. The results from pharmacokinetic calculations showed that both the distribution volume at steady state (V (dss)) and body clearance (CL(tot)) were affected in febrile as compared to healthy animals. The mean values of V (dss) and CL(tot) of cefepime in healthy rabbits were 1.168 L/kg and 0.303 L/kg/h, respectively. As compared with healthy animals, the mean estimates of V (dss) (0.917 L/kg) and CL(tot) (0.205 L/kg per h) of cefepime were significantly lower, whereas t (1/2lambda), MRT and AUMC were significantly higher in febrile rabbits. It is concluded that, although experimental infection had an effect on the disposition kinetics of cefepime in healthy and febrile rabbits, this was not sufficiently pronounced to require alteration of the dosage during disease.

Influence of endotoxin induced fever on the pharmacokinetics of intramuscularly administered cefepime in rabbits

This study examined the effect of experimentally induced fever on the pharmacokinetics of cefepime (75 mg/kg BW) administered intramuscularly to six rabbits. The study was carried out in two consecutive phases separated by a two-week washout period. An infection was induced by an intravenous inoculation of 5 × 10⁸ colony-forming units of Escherichia coli 24 h before the pharmacokinetic investigation. A quantitative microbiological assay was employed to measure the plasma cefepime concentrations using an agar-gel diffusion method with Bacillus subtilis ATCC 6633 as the test organism. Twenty-four hour after the injection, the rectal temperature in the infected animals increased by 1–. There was a significant reduction in the elimination half-life by 21.8% in the febrile rabbits compared to healthy animals. In addition, the infection significantly increased the peak plasma concentrations by 11.9%, the mean residence time by 19.9%, the area under the plasma-concentration-time curve by 53.6% and the area under the moment curve by 62.3%. In conclusion, the endotoxin-induced febrile state produced significant changes in the plasma levels as well as some of the pharmacokinetic variables of cefepime in rabbits.

Pharmacokinetics of cefepime administered by i.v. and i.m. routes to ewes

The pharmacokinetics of cefepime were studied following i.v. and i.m. administration of 20 mg/kg in 10 ewes. Following i.v. administration of a single dose, the plasma concentration-time curves of cefepime were best fitted using a two-compartment open model. The elimination half-life (t(1/2beta)) was 1.76 +/- 0.07 h, volume of distribution at steady-state [V(d(ss))] was 0.32 +/- 0.01 L/kg and total body clearance (Cl(B)) was 2.37 +/- 0.05 mL/min.kg. Following i.m. administration, the drug was rapidly absorbed with an absorption half-life (t(1/2ab)) of 0.49 +/- 0.05 h, maximum plasma concentration (Cmax) of 31.9 +/- 1.5 mug/mL was attained at (tmax) 1.1 +/- 0.2 h and the drug was eliminated with an elimination half-life (t(1/2el)) of 2.06 +/- 0.11 h. The systemic bioavailability (F) after i.m. administration of cefepime was 86.8 +/- 7.5%. The extent of plasma protein binding measured in vitro was 14.8 +/- 0.54%. The drug was detected in urine for 36 h postadministration by both routes.