Iranian Journal of Pharmacology & Therapeutics, Vol. 5, No. 2, 2006, pp. 127-130

Research Article

Urvesh D Patel, Shailesh K Bhavsar and Aswin M Thaker

Current Author Addresses: Dr. Urvesh D Patel, Department of Pharmacology and Toxicology, College of Veterinary Science and A.H., Anand Agricultural University, Anand-388001, Gujarat state (INDIA). E-mail: urvesh1981@yahoo.com.
Dr. Shailesh K Bhavsar, Department of Pharmacology and Toxicology, College of Veterinary Science and A.H., Anand Agricultural University, Anand-388001, Gujarat state (INDIA). Phone: 0091 2692 2646880091 2692 261486 (Fax) E-mail: skbhavsar@aau.in (Corresponding Author).
Dr. Aswin M Thaker, Department of Pharmacology and Toxicology, College of Veterinary Science and A.H., Anand Agricultural University, Anand-388001, Gujarat state (INDIA). E-mail: aswinthaker@hotmail.com.

Received May 11, 2006; Revised October 5, 2006; Accepted November 7, 2006

Code Number: pt06021

ABSTRACT

Pharmacokinetics of cefepimewas studied after single dose intravenous administration at the dose rate of 5 mg/kg body weight in calves. Blood samples were collected from the jugular vein at predetermined time intervals before and after drug administration. Serum was harvested and analysed for cefepimeconcentration by reverse-phase high performance liquid chromatography. Following intravenous administration, the mean serum cefepimelevel of 44.93 ± 5.47 μg/mL was observed at 0.033 h (2 minutes). The therapeutically effective concentration of cefepime(≥ 1.00 μg/mL) was maintained in serum up to 12 h. The distribution half-life (t_1/2a) and elimination half-life (t_1/2β) were 0.09 ± 0.01 hand 3.70 ± 0.16 h, respectively. The mean values of apparent volume of distribution [V_d(area)] and volume of distribution of drug at steady-state (V_{d (ss)}) were calculated to be 0.57 ± 0.03 and 0.43 ± 0.03 L/kg, respectively. The mean value of total body clearance (Cl_B) was 1.81 ± 0.16 mL/min/kg. The average values for area under serum drug concentration-time curve (AUC) and area under first moment of curve (AUMC) were 47.73 ± 4.05 μgh/mL and 190.3 ± 19.9 μg h²/mL. The average value of mean residence time (MRT) was 3.95 ± 0.11 h. A satisfactory intravenous dosage regimen would be 4.20 mg/kg body weight as priming dose followed by 3.78 mg/kg repeated at 12 h intervals.

Keywords: Cefepime, Calves, Pharmacokinetics, Intravenous

Cefepime, a semi-synthetic, parenteral fourth-generation cephalosporin antibiotic, has a broad spectrum of activity against a wide range of Gram-positive and Gram–negative bacteria. Cefepimeexhibits increased stability against hydrolysis by class 1 chromosomally mediated b- lactamases. Cefepimeshows excellent activity against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterococcus cloacae, Staphylococcus aureus and Estreptococcus spp. [1] but lacks activity against methicillin-resistant Staphylococci and Enterococci. It has variable activity against anaerobic bacteria [18].

Cefepimeis well tolerated and effective against infections of soft tissues, the abdominal cavity, urinary tract, lower respiratory tract and provides efficacious antibacterial prophylaxis for biliary tract and prostate surgery [10, 11]. Cefepimepharmacokinetics have previously been studied in adult horses [5], neonatal foals and dogs [3, 15], goats [13] and cow calves [6]. Cefepimeis a highly effective antibiotic against Gram-negative bacteria including those resistant to third generation cephalosporins [12, 14, 16]. Diseases like coliform septicaemia, pneumonia, colibacillosis and meningitis are major causes of neonatal calf mortality where it can be used for treatment. Therefore, the present study was planned to determine various pharmacokinetic parameters of cefepimeand to predict its dosage regimen following single dose intravenous administration in cow calves.

Materials and Methods

Experimental Animals

The experiment was conducted on six healthy young (4-6 months of age) Holstein-Friesian (H.F.) calves (Bos taurus L.), weighing 57-80 kg. The animals were examined clinically to evaluate health status and to rule out the possibility of any diseases. Each calf was housed in a separate pen and provided standard ration. Water was provided ad libitum.

Pure cefepimepowder was obtained from Aurobindo Pharma Ltd., Hyderabad, India. Cefepimehydrochloride (Novapime, Lupin Ltd., Mumbai, India) equivalent to 1 gcefepime. was purchased from pharmacy. Water, sodium acetate, acetic acid, acetonitrile and perchloric acid (70%) of HPLC grade were procured from Merck India Ltd., Mumbai.

All six animals were randomly allocated to receive intravenous injection of cefepime. Cefepimehydrochloride (Novapime, Lupin Ltd, Mumbai, India) was diluted with sterile water to make concentration of 100 mg/mL and administered at a dose rate of 5 mg/kg body weight. Intravenous injection of the drug was given through left jugular vein, using a 20 G ´ 25 mm needle. Blood samples (4-5 mL) were collected from the right jugular vein through a fixed catheter prior to injection and at 2, 5, 10, 15, 30 min and 1, 2, 4, 6, 8, 12, 18 and 24, h following intravenous administration of cefepime. Calves were observed for any adverse reactions during the study after administration of drug.

Blood samples were allowed to clot and the serum was harvested by centrifugation at 5000 revolution per min for 15 min. The serum samples were stored at – 40 °C until drug analysis was performed.

Cefepimeconcentration in serum samples was determined by reverse-phase High Performance Liquid Chromatography (HPLC) after extraction, using a reported assay (Gardner and Papich, 2001) with some modifications.

The HPLC system (Knauer, Germany) comprised of isocratic solvent delivery pump (model K 501) and UV detector (model K 2501). Chromatographic separations were performed by using reverse phase C18 column (Zorbax, ODS; 25 cm ´ 46 mm ID) at room temperature. Data integration was performed using Eurochrome software (Version 2000).

The mobile phase was a mixture of 0.2 M sodium acetate (3.2%), 0.2 M acetic acid (2.2 %), acetronitrile (10.0 %) and HPLC water (84.6 %) with pH 5.1. Mobile phase was filtered through a 0.45 μ filter and pumped into column at a flow rate of 1.5 mL/min at ambient temperature. The eluate was monitored at 257 nm wavelength.

Serum samples were deproteinized by diluting 500 μl of serum with 500 μl of 0.8 M perchloric acid and centrifuged at 5000 revolution per minute for 10 minutes. The clean supernant was collected and an aliquot of 20 μl of this supernant was injected into the loop of HPLC system through manual injector.

Calibration curve was prepared by adding known amount of cefepimeto blank unfortified serum for the expected range of concentrations from 0.1 to 100 μg/mL. Quantification was done by reference to the resultant calibration curve. The calibration curve were prepared daily and not accepted unless it had a R² value > 0.99. The lower limit of quantitation was 0.5 μg/mL. The assay was sensitive, reproducible and linearity was observed from 0.5 to 100 μg/mL. The typical chromatogram of cefepimein calf serum is shown in Fig 1. The retention time of cefepimewas 5.0 minutes.

The comparative disposition of cefepimefollowing single dose intravenous administration in cow calves was plotted on semi logarithmic scale (Fig 2). Various pharmacokinetic parameters calculated from serum concentration of cefepimeafter its single dose intravenous administrations are summarized in Table 1. Various intravenous dosage regimens were computed and are presented in Table 2.

Pharmacokinetic studies of cefepimefollowing intravenous and/or intramuscular administration have been reported in cow calves [6], foals and dogs [3, 15], horses [5] and goats [13]. Following intravenous administration of cefepimeat the dose of 5 mg/kg, no adverse reactions were observed in calves in the present study; however some adverse effects have been reported in dogs [3, 15], foals [3], and horses [5].

Following intravenous administration, cefepimeserum concentration versus time data can be best fitted to a two-compartment open model, which was similar to the disposition characteristics of cefepimeobserved in human [9], and other animal species [3, 5, 6]. In the present study, the peak and minimal detectable levels of 44.93 ± 5.47 and 1.01 ±0.07 µg/mL of cefepimewere measured at 0.033 and 12 h, respectively. The Therapeutic concentration of cefepime ≥ 1.0 µg/mL [2, 7, 8, 17] was maintained in serum up to 12 h.

The drug was rapidly distributed with a short distribution half-life (t_1/2a) of 0.09 ± 0.01 h, this value was shorter than values of 0.20 ± 0.02 h in cow calves [6], 0.36 ± 0.18 h in horses [5], 0.39 ± 0.21 h in dogs [3] and 0.30 ± 0.16 h in foals [3]. The rapid distribution was further supported by high value of K₁₂/K₂₁ (3.84 ± 0.65). The elimination half-life (t_1/2β) in this study (3.70 ± 0.16 h) was longer than the values of 2.38 ± 0.16 h and 2.1 ± 1.25 h in cow calves [6] and horses [5], respectively. In contrast the drug was rapidly eliminated in foals (t_{1/2 β}: 1.65 ± 0.10 h) and dogs (t_{1/2 β}: 1.09 ± 0.27 h) [3]. Low value of elimination rate constant (β: 0.19 ± 0.01 h^-1) observed in present study was comparable to the value of 0.29 ± 0.02 h^-1 in cow calves [6] while lower than 0.36± 0.18 h^-1 in horses [5], 0.42 ± 0.03 h^-1 in foals 0.79 ± 0.08 h^-1 in dogs [3] indicated that the elimination of cefepimeis slower in horses, foals and dogs.

The value of mean residence time (3.95 ± 0.11 h) was almost similar to that of 3.38 ± 0.26 h reported in cow calves [6], but longer than the values of 2.03 ± 1.07, 2.16 ± 0.13 and 1.05 ± 0.14 h reported in horses [5], foals and dogs [3], respectively.

The area under curve (AUC) was calculated to be 47.73 ± 4.05 μg h/mLwhich was much lower than the values of 94.5 ± 7.6, 114.8 ± 36.62 and 182.47 ± 59.7 μg h/mLreported in cow calves [6], dogs and foals [3], respectively. The volume of distribution at steady state (Vd_ss: 0.43 ± 0.03 L/Kg) was higher than the values of 0.21 ± 0.01 L/kg in cow calves [6], 0.14 ± 0.04 L/kgin dogs and 0.18 ± 0.05 L/kg in foals [3] indicating good extravascular distribution in cow calves.

Total body clearance (Cl_B) in present study (1.81 ± 0.16 mL/min/kg) was comparable to value of 2.16 ± 0.66 mL/min/kg reported in dogs [3] but was slightly higher than 1.1 ± 0.08, 1.33 ± 0.33, and 1.18 ± 0.18 mL/min/kg reported in cow calves [6], foals [3], and horses [5], respectively.

The important objective of the present study was to compute a satisfactory dosage regimen of cefepimein cow calves. Thus appropriate dosage regimen of cefepimeon the basis of pharmacokinetic data was calculated for calves. For cefepimethe minimum inhibitory concentration against majority of Gram-negative and Gram-positive pathogens has been reported to be ≤ 1.0 μg/mL [2, 7, 8, 17]. A satisfactory intravenous dosage regimen would be 4.20 mg/kg body weight as priming dose followed by maintenance doses of 3.78 mg/kg body weight per 12 h to maintain the therapeutic drug concentration (≥ 0.1 mg/mL).

References

 Copyright © 2006 by Razi Institute for Drug Research (RIDR)