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Maxipime

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Maxipime

CLINICAL PHARMACOLOGY

Cefepime is an antibacterial agent belonging to the cephalosporin class of antibacterials with in vitro antibacterial activity against facultative Gram-positive and Gram-negative bacteria.

Pharmacokinetics

The average plasma concentrations of cefepime observed in healthy adult male volunteers (n=9) at various times following single 30-minute infusions (IV) of cefepime 500 mg, 1 g, and 2 g are summarized in Table 1. Elimination of cefepime is principally via renal excretion with an average (±SD) half-life of 2 (±0.3) hours and total body clearance of 120 (±8) mL/min in healthy volunteers. Cefepime pharmacokinetics are linear over the range 250 mg to 2 g. There is no evidence of accumulation in healthy adult male volunteers (n=7) receiving clinically relevant doses for a period of 9 days.

Absorption

The average plasma concentrations of cefepime and its derived pharmacokinetic parameters after intravenous (IV) administration are portrayed in Table 1.

Table 1: Average Plasma Concentrations in mcg/mL of Cefepime and Derived Pharmacokinetic Parameters (±SD), Intravenous Administration

Parameter MAXIPIME
500 mg IV 1 g IV 2 g IV
0.5 h 38.2 78.7 163.1
1 h 21.6 44.5 85.8
2 h 11.6 24.3 44.8
4 h 5 10.5 19.2
8 h 1.4 2.4 3.9
12 h 0.2 0.6 1.1
Cmax, mcg/mL 39.1 (3.5) 81.7 (5.1) 163.9 (25.3)
AUC,h•mcg/mL 70.8 (6.7) 148.5 (15.1) 284.8 (30.6)
Number of subjects (male) 9 9 9

Following intramuscular (IM) administration, cefepime is completely absorbed. The average plasma concentrations of cefepime at various times following a single intramuscular injection are summarized in Table 2. The pharmacokinetics of cefepime are linear over the range of 500 mg to 2 g intramuscularly and do not vary with respect to treatment duration.

Table 2: Average Plasma Concentrations in mcg/mL of Cefepime and Derived Pharmacokinetic Parameters (±SD), Intramuscular Administration

Parameter MAXIPIME
500 mg IM 1 g IM 2 g IM
0.5 h 8.2 14.8 36.1
1 h 12.5 25.9 49.9
2 h 12 26.3 51.3
4 h 6.9 16 31.5
8 h 1.9 4.5 8.7
12 h 0.7 1.4 2.3
Cmax, mcg/mL 13.9 (3.4) 29.6 (4.4) 57.5 (9.5)
Tmax, h 1.4 (0.9) 1.6 (0.4) 1.5 (0.4)
AUC, h•mcg/mL 60 (8) 137 (11) 262 (23)
Number of subjects (male) 6 6 12

Distribution

The average steady-state volume of distribution of cefepime is 18 (±2) L. The serum protein binding of cefepime is approximately 20% and is independent of its concentration in serum.

Cefepime is excreted in human milk. A nursing infant consuming approximately 1000 mL of human milk per day would receive approximately 0.5 mg of cefepime per day. (See PRECAUTIONS: Nursing Mothers.)

Concentrations of cefepime achieved in specific tissues and body fluids are listed in Table 3.

Table 3: Average Concentrations of Cefepime in Specific Body Fluids (mcg/mL) or Tissues (mcg/g)

Tissue or Fluid Dose/Route # of Patients Average Time of Sample Post-Dose (h) Average Concentration
Blister Fluid 2 g IV 6 1.5 81.4 mcg/mL
Bronchial Mucosa 2 g IV 20 4.8 24.1 mcg/g
Sputum 2 g IV 5 4 7.4 mcg/mL
Urine 500 mg IV 8 0 to 4 292 mcg/mL
1 g IV 12 0 to 4 926 mcg/mL
2 g IV 12 0 to 4 3120 mcg/mL
Bile 2 g IV 26 9.4 17.8 mcg/mL
Peritoneal Fluid 2 g IV 19 4.4 18.3 mcg/mL
Appendix 2 g IV 31 5.7 5.2 mcg/g
Gallbladder 2 g IV 38 8.9 11.9 mcg/g
Prostate 2 g IV 5 1 31.5 mcg/g

Data suggest that cefepime does cross the inflamed blood-brain barrier. The clinical relevance of these data is uncertain at this time.

Metabolism and Excretion

Cefepime is metabolized to N-methylpyrrolidine (NMP) which is rapidly converted to the N-oxide (NMP-N-oxide). Urinary recovery of unchanged cefepime accounts for approximately 85% of the administered dose. Less than 1% of the administered dose is recovered from urine as NMP, 6.8% as NMP-N-oxide, and 2.5% as an epimer of cefepime. Because renal excretion is a significant pathway of elimination, patients with renal dysfunction and patients undergoing hemodialysis require dosage adjustment. (See DOSAGE AND ADMINISTRATION.)

Specific Populations

Renal impairment: Cefepime pharmacokinetics have been investigated in patients with various degrees of renal impairment (n=30). The average half-life in patients requiring hemodialysis was 13.5 (±2.7) hours and in patients requiring continuous peritoneal dialysis was 19 (±2) hours. Cefepime total body clearance decreased proportionally with creatinine clearance in patients with abnormal renal function, which serves as the basis for dosage adjustment recommendations in this group of patients. (See DOSAGE AND ADMINISTRATION.)

Hepatic impairment: The pharmacokinetics of cefepime were unaltered in patients with hepatic impairment who received a single 1 g dose (n=11).

Geriatric patients: Cefepime pharmacokinetics have been investigated in elderly (65 years of age and older) men (n=12) and women (n=12) whose mean (SD) creatinine clearance was 74 (±15) mL/min. There appeared to be a decrease in cefepime total body clearance as a function of creatinine clearance. Therefore, dosage administration of cefepime in the elderly should be adjusted as appropriate if the patient's creatinine clearance is 60 mL/min or less. (See DOSAGE AND ADMINISTRATION.)

Pediatric patients: Cefepime pharmacokinetics have been evaluated in pediatric patients from 2 months to 11 years of age following single and multiple doses on every 8 hours (n=29) and every 12 hours (n=13) schedules. Following a single intravenous dose, total body clearance and the steady-state volume of distribution averaged 3.3 (±1) mL/min/kg and 0.3 (±0.1) L/kg, respectively. The urinary recovery of unchanged cefepime was 60.4 (±30.4)% of the administered dose, and the average renal clearance was 2 (±1.1) mL/min/kg. There were no significant effects of age or gender (25 male vs 17 female) on total body clearance or volume of distribution, corrected for body weight. No accumulation was seen when cefepime was given at 50 mg per kg every 12 hours (n=13), while Cmax, AUC, and t½ were increased about 15% at steady state after 50 mg per kg every 8 hours. The exposure to cefepime following a 50 mg per kg intravenous dose in a pediatric patient is comparable to that in an adult treated with a 2 g intravenous dose. The absolute bioavailability of cefepime after an intramuscular dose of 50 mg per kg was 82.3 (±15)% in eight patients.

Microbiology

Cefepime is a bactericidal agent that acts by inhibition of bacterial cell wall synthesis. Cefepime has a broad spectrum of in vitro activity that encompasses a wide range of Gram-positive and Gram-negative bacteria. Cefepime has a low affinity for chromosomally-encoded beta-lactamases. Cefepime is highly resistant to hydrolysis by most beta-lactamases and exhibits rapid penetration into Gram-negative bacterial cells. Within bacterial cells, the molecular targets of cefepime are the penicillin binding proteins (PBP).

Cefepime has been shown to be active against most isolates of the following microorganisms, both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section.

Aerobic Gram-Negative Microorganisms

Enterobacter
Escherichia coli

Klebsiella pneumoniae

Proteus mirabilis

Pseudomonas aeruginosa

Aerobic Gram-Positive Microorganisms

Staphylococcus aureus (methicillin-susceptible isolates only)
Streptococcus pneumoniae

Streptococcus pyogenes
(Lancefield's Group A streptococci)
Viridans group streptococci

The following in vitro data are available, but their clinical significance is unknown. Cefepime has been shown to have in vitro activity against most isolates of the following microorganisms; however, the safety and effectiveness of cefepime in treating clinical infections due to these microorganisms have not been established in adequate and well-controlled trials.

Aerobic Gram-Positive Microorganisms

Staphylococcus epidermidis (methicillin-susceptible isolates only)
Staphylococcus saprophyticus

Streptococcus agalactiae
(Lancefield's Group B streptococci)

NOTE: Most isolates of enterococci, eg, Enterococcus faecalis, and methicillin-resistant staphylococci are resistant to cefepime.

Aerobic Gram-Negative Microorganisms

Acinetobacter calcoaceticus subsp. lwoffii
Citrobacter diversus

Citrobacter freundii

Enterobacter agglomerans

Haemophilus influenzae
(including beta-lactamase producing isolates)
Hafnia alvei

Klebsiella oxytoca

Moraxella catarrhalis
(including beta-lactamase producing isolates)
Morganella morganii

Proteus vulgaris

Providencia rettgeri

Providencia stuartii

Serratia marcescens

NOTE: Cefepime is inactive against many isolates of Stenotrophomonas (formerly Xanthomonas maltophilia and Pseudomonas maltophilia).

Anaerobic Microorganisms

NOTE: Cefepime is inactive against most isolates of Clostridium difficile.

Susceptibility Tests

Dilution Techniques

Quantitative methods are used to determine antimicrobial minimum inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized procedure. Standardized procedures are based on a dilution method1 (broth or agar) or equivalent with standardized inoculum concentrations and standardized concentrations of cefepime powder. The MIC values should be interpreted according to the following criteria:

Table 4

Microorganism MIC (mcg/mL)
Susceptible (S) Intermediate (I) Resistant (R)
Microorganisms other than  Haemophilus spp.* and  Streptococcus pneumoniae* ≤ 8 16 ≥ 32
Haemophilus spp.* ≤ 2 _* _*
S. pneumoniae * ≤ 0.5 1 ≥ 2
*NOTE: Isolates from these species should be tested for susceptibility using specialized dilution testing methods.1 Also, isolates of Haemophilus spp. with MICs greater than 2 mcg/mL should be considered equivocal and should be further evaluated.

A report of “Susceptible” indicates that the pathogen is likely to be inhibited if the antimicrobial compound in the blood reaches the concentrations usually achievable. A report of “Intermediate” indicates that the result should be considered equivocal, and, if the microorganism is not fully susceptible to alternative, clinically feasible drugs, the test should be repeated. This category implies possible clinical applicability in body sites where the drug is physiologically concentrated or in situations where high dosage of drug can be used. This category also provides a buffer zone which prevents small uncontrolled technical factors from causing major discrepancies in interpretation. A report of “Resistant” indicates that the pathogen is not likely to be inhibited if the antimicrobial compound in the blood reaches the concentrations usually achievable; other therapy should be selected.

Standardized susceptibility test procedures require the use of laboratory control microorganisms to control the technical aspects of the laboratory procedures. Laboratory control microorganisms are specific strains of microbiological assay organisms with intrinsic biological properties relating to resistance mechanisms and their genetic expression within bacteria; the specific strains are not clinically significant in their current microbiological status. Standard cefepime powder should provide the following MIC values (Table 5) when tested against the designated quality control strains:

Table 5

Microorganism ATCC MIC (mcg/mL)
Escherichia coli 25922 0.016 to 0.12
Staphylococcus aureus 29213 1 to 4
Pseudomonas aeruginosa 27853 1 to 4
Haemophilus influenzae 49247 0.5 to 2
Streptococcus pneumoniae 49619 0.06 to 0.25

Diffusion Techniques

Quantitative methods that require measurement of zone diameters also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure2 requires the use of standardized inoculum concentrations. This procedure uses paper disks impregnated with 30 mcg of cefepime to test the susceptibility of microorganisms to cefepime. Interpretation is identical to that stated above for results using dilution techniques.

Reports from the laboratory providing results of the standard single-disk susceptibility test with a 30-mcg cefepime disk should be interpreted according to the following criteria:

Table 6

Microorganism Zone Diameter (mm)
Susceptible (S) Intermediate (I) Resistant (R)
Microorganisms other than Haemophilus spp.* and S. pneumoniae* ≥ 18 15 to 17 ≤ 14
Haemophilus spp.* ≥ 26 _* _*

*NOTE: Isolates from these species should be tested for susceptibility using specialized diffusion testing methods.2 Isolates of Haemophilus spp. with zones smaller than 26 mm should be considered equivocal and should be further evaluated. Isolates of S. pneumoniae should be tested against a 1-mcg oxacillin disk; isolates with oxacillin zone sizes larger than or equal to 20 mm may be considered susceptible to cefepime.

As with standardized dilution techniques, diffusion methods require the use of laboratory control microorganisms to control the technical aspects of the laboratory procedures. Laboratory control microorganisms are specific strains of microbiological assay organisms with intrinsic biological properties relating to resistance mechanisms and their genetic expression within bacteria; the specific strains are not clinically significant in their current microbiological status. For the diffusion technique, the 30 mcg cefepime disk should provide the following zone diameters in these laboratory test quality control strains (Table 7):

Table 7

Microorganism ATCC Zone Size Range (mm)
Escherichia coli 25922 29 to 35
Staphylococcus aureus 25923 23 to 29
Pseudomonas aeruginosa 27853 24 to 30
Haemophilus influenzae 49247 25 to 31

Clinical Studies

Febrile Neutropenic Patients

The safety and efficacy of empiric cefepime monotherapy of febrile neutropenic patients have been assessed in two multicenter, randomized trials comparing cefepime monotherapy (at a dose of 2 g intravenously every 8 hours) to ceftazidime monotherapy (at a dose of 2 g intravenously every 8 hours). These studies comprised 317 evaluable patients. Table 8 describes the characteristics of the evaluable patient population.

Table 8: Demographics of Evaluable Patients (First Episodes Only)

Total Cefepime 164 Ceftazidime 153
Median age (yr) 56 (range, 18 to 82) 55 (range, 16 to 84)
Male 86 (52%) 85 (56%)
Female 78 (48%) 68 (44%)
Leukemia 65 (40%) 52 (34%)
Other hematologic malignancies 43 (26%) 36 (24%)
Solid tumor 54 (33%) 56 (37%)
Median ANC nadir (cells/microliter) 20 (range, 0 to 500) 20 (range, 0 to 500)
Median duration of neutropenia (days) 6 (range, 0 to 39) 6 (range, 0 to 32)
Indwelling venous catheter 97 (59%) 86 (56%)
Prophylactic antibiotics 62 (38%) 64 (42%)
Bone marrow graft 9 (5%) 7 (5%)
SBP less than 90 mm Hg at entry 7 (4%) 2 (1%)
ANC = absolute neutrophil count; SBP = systolic blood pressure

Table 9 describes the clinical response rates observed. For all outcome measures, cefepime was therapeutically equivalent to ceftazidime.

Table 9: Pooled Response Rates for Empiric Therapy of Febrile Neutropenic Patients

Outcome Measures % Response
Cefepime
(n=164)
Ceftazidime
(n=153)
Primary episode resolved with no treatment modification, no new febrile episodes or infection, and oral antibiotics allowed for completion of treatment 51 55
Primary episode resolved with no treatment modification, no new febrile episodes or infection and no post-treatment oral antibiotics 34 39
Survival, any treatment modification allowed 93 97
Primary episode resolved with no treatment modification and oral antibiotics allowed for completion of treatment 62 67
Primary episode resolved with no treatment modification and no post-treatment oral antibiotics 46 51

Insufficient data exist to support the efficacy of cefepime monotherapy in patients at high risk for severe infection (including patients with a history of recent bone marrow transplantation, with hypotension at presentation, with an underlying hematologic malignancy, or with severe or prolonged neutropenia). No data are available in patients with septic shock.

Complicated Intra-Abdominal Infections

Patients hospitalized with complicated intra-abdominal infections participated in a randomized, double-blind, multicenter trial comparing the combination of cefepime (2 g every 12 hours) plus intravenous metronidazole (500 mg every 6 hours) versus imipenem/cilastatin (500 mg every 6 hours) for a maximum duration of 14 days of therapy. The study was designed to demonstrate equivalence of the two therapies. The primary analyses were conducted on the protocol-valid population, which consisted of those with a surgically confirmed complicated infection, at least one pathogen isolated pretreatment, at least 5 days of treatment, and a 4 to 6 week follow-up assessment for cured patients. Subjects in the imipenem/cilastatin arm had higher APACHE II scores at baseline. The treatment groups were otherwise generally comparable with regard to their pretreatment characteristics. The overall clinical cure rate among the protocol-valid patients was 81% (51 cured/63 evaluable patients) in the cefepime plus metronidazole group and 66% (62/94) in the imipenem/cilastatin group. The observed differences in efficacy may have been due to a greater proportion of patients with high APACHE II scores in the imipenem/cilastatin group.

REFERENCES

1. National Committee for Clinical Laboratory Standards. Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically—Third Edition. Approved Standard NCCLS Document M7-A3, Vol. 13, No. 25, NCCLS, Villanova, PA, December 1993.

2. National Committee for Clinical Laboratory Standards. Performance Standards for Antimicrobial Disk Susceptibility Tests—Fifth Edition. Approved Standard NCCLS Document M2-A5, Vol. 13, No. 24, NCCLS, Villanova, PA, December 1993.

Last reviewed on RxList: 9/20/2012
This monograph has been modified to include the generic and brand name in many instances.

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