CLINICAL PHARMACOLOGY
Mechanism Of Action
CEFTIN is an antibacterial drug [see Microbiology].
Pharmacokinetics
Absorption
After oral administration, cefuroxime axetil is absorbed
from the gastrointestinal tract and rapidly hydrolyzed by nonspecific esterases
in the intestinal mucosa and blood to cefuroxime. Serum pharmacokinetic
parameters for cefuroxime following administration of CEFTIN tablets to adults
are shown in Table 8.
Table 8: Pharmacokinetics of Cefuroxime Administered
in the Postprandial State as CEFTIN Tablets to Adultsa
Doseb (Cefuroxime Equivalent) |
Peak Plasma Concentration (mcg/mL) |
Time of Peak Plasma Concentration (h) |
Mean Elimination Half-life (h) |
AUC (mcg•h/mL) |
125 mg |
2.1 |
2.2 |
1.2 |
6.7 |
250 mg |
4.1 |
2.5 |
1.2 |
12.9 |
500 mg |
7.0 |
3.0 |
1.2 |
27.4 |
1,000 mg |
13.6 |
2.5 |
1.3 |
50.0 |
a Mean values of 12 healthy adult volunteers.
b Drug administered immediately after a meal. |
Food Effect
Absorption of the tablet is greater when taken after food
(absolute bioavailability increases from 37% to 52%). Despite this difference
in absorption, the clinical and bacteriologic responses of subjects were
independent of food intake at the time of tablet administration in 2 trials
where this was assessed.
All pharmacokinetic and clinical effectiveness and safety
trials in pediatric subjects using the suspension formulation were conducted in
the fed state. No data are available on the absorption kinetics of the
suspension formulation when administered to fasted pediatric subjects.
Lack Of Bioequivalence
Oral suspension was not bioequivalent to tablets when
tested in healthy adults. The tablet and oral suspension formulations are NOT
substitutable on a milligram-permilligram basis. The area under the curve for
the suspension averaged 91% of that for the tablet, and the peak plasma
concentration for the suspension averaged 71% of the peak plasma concentration
of the tablets. Therefore, the safety and effectiveness of both the tablet and
oral suspension formulations were established in separate clinical trials.
Distribution
Cefuroxime is distributed throughout the extracellular
fluids. Approximately 50% of serum cefuroxime is bound to protein.
Metabolism
The axetil moiety is metabolized to acetaldehyde and
acetic acid.
Excretion
Cefuroxime is excreted unchanged in the urine; in adults,
approximately 50% of the administered dose is recovered in the urine within 12
hours. The pharmacokinetics of cefuroxime in pediatric subjects have not been
studied. Until further data are available, the renal elimination of cefuroxime
axetil established in adults should not be extrapolated to pediatric subjects.
Specific Populations
Renal Impairment
In a trial of 28 adults with normal renal function or
severe renal impairment (creatinine clearance <30 mL/min), the elimination
half-life was prolonged in relation to severity of renal impairment.
Prolongation of the dosage interval is recommended in adult patients with creatinine
clearance <30 mL/min [see DOSAGE AND ADMINISTRATION].
Pediatric Patients
Serum pharmacokinetic parameters for cefuroxime in
pediatric subjects administered CEFTIN for oral suspension are shown in Table
9.
Table 9: Pharmacokinetics of Cefuroxime Administered
in the Postprandial State as CEFTIN for Oral Suspension to Pediatric Subjectsa
Doseb (Cefuroxime Equivalent) |
n |
Peak Plasma Concentration (mcg/mL) |
Time of Peak Plasma Concentration (h) |
Mean Elimination Half-life (h) |
AUC (mcg•h/mL) |
10 mg/kg |
8 |
3.3 |
3.6 |
1.4 |
12.4 |
15 mg/kg |
12 |
5.1 |
2.7 |
1.9 |
22.5 |
20 mg/kg |
8 |
7.0 |
3.1 |
1.9 |
32.8 |
a Mean age = 23 months.
b Drug administered with milk or milk products. |
Geriatric Patients
In a trial of 20 elderly subjects (mean age = 83.9 years)
having a mean creatinine clearance of 34.9 mL/min, the mean serum elimination
half-life was prolonged to 3.5 hours; however, despite the lower elimination of
cefuroxime in geriatric patients, dosage adjustment based on age is not
necessary [see Use In Specific Populations].
Drug Interactions
Concomitant administration of probenecid with cefuroxime
axetil tablets increases the cefuroxime area under the serum concentration
versus time curve and maximum serum concentration by 50% and 21%, respectively.
Microbiology
Mechanism Of Action
Cefuroxime axetil is a bactericidal agent that acts by
inhibition of bacterial cell wall synthesis. Cefuroxime axetil has activity in
the presence of some β-lactamases, both penicillinases and cephalosporinases,
of gram-negative and gram-positive bacteria.
Mechanism Of Resistance
Resistance to cefuroxime axetil is primarily through
hydrolysis by β-lactamase, alteration of penicillin-binding proteins (PBPs),
decreased permeability, and the presence of bacterial efflux pumps.
Susceptibility to cefuroxime axetil will vary with
geography and time; local susceptibility data should be consulted, if
available. Beta-lactamase-negative, ampicillin-resistant (BLNAR) isolates of H.
influenzae should be considered resistant to cefuroxime axetil.
Cefuroxime axetil has been shown to be active against
most isolates of the following bacteria, both in vitro and in clinical
infections [see INDICATIONS AND USAGE]:
Gram-Positive Bacteria
Staphylococcus aureus (methicillin-susceptible isolates
only)
Streptococcus pneumoniae
Streptococcus pyogenes
Gram-Negative Bacteria
Escherichia colia
Klebsiella pneumoniaea
Haemophilus influenzae
Haemophilus parainfluenzae
Moraxella catarrhalis
Neisseria gonorrhoeae
a Most extended spectrum β-lactamase
(ESBL)-producing and carbapenemase-producing isolates are resistant to
cefuroxime axetil.
Spirochetes
Borrelia Burgdorferi
The following in vitro data are available, but their
clinical significance is unknown. At least 90 percent of the following
microorganisms exhibit an in vitro minimum inhibitory concentration (MIC) less
than or equal to the susceptible breakpoint for cefuroxime axetil of 1 mcg/mL. However,
the efficacy of cefuroxime axetil in treating clinical infections due to these microorganisms
has not been established in adequate and well-controlled clinical trials.
Gram-Positive Bacteria
Staphylococcus epidermidis (methicillin-susceptible
isolates only)
Staphylococcus saprophyticus (methicillin-susceptible
isolates only)
Streptococcus agalactiae
Gram-Negative Bacteria
Morganella morganii
Proteus inconstans
Proteus mirabilis
Providencia rettgeri
Anaerobic Bacteria
Peptococcus niger
Susceptibility Test Methods
When available, the clinical microbiology laboratory
should provide the results of in vitro susceptibility tests for antimicrobial
drug products used in local hospitals and practice areas to the physician as
periodic reports that describe the susceptibility profile of nosocomial and community-acquired
pathogens. These reports should aid the physician in selecting an antibacterial
drug product for treatment.
Dilution Techniques
Quantitative methods are used to determine antimicrobial
MICs. These MICs provide reproducible estimates of the susceptibility of
bacteria to antimicrobial compounds. The MICs should be determined using a
standardized test method (broth or agar).1, 2 The MIC values should
be interpreted according to criteria provided in Table 10.2,3
Diffusion Techniques
Quantitative methods that require measurement of zone
diameters also provide reproducible estimates of the susceptibility of bacteria
to antimicrobial compounds. The zone size provides an estimate of the
susceptibility of bacteria to antimicrobial compounds. The zone size should be
determined using a standardized test method.4 This procedure uses paper disks
impregnated with 30 mcg cefuroxime axetil to test the susceptibility of
microorganisms to cefuroxime axetil. The disk diffusion interpretive criteria
are provided in Table 10.3
Table 10: Susceptibility Test Interpretive Criteria for
Cefuroxime Axetil
Pathogen |
Minimum Inhibitory Concentrations (mcg/mL) |
Disk Diffusion Zone Diameters (mm) |
(S) Susceptible |
(I) Intermediate |
(R) Resistant |
(S) Susceptible |
(I) Intermediate |
(R) Resistant |
Enterobacteriaceaea |
≤4 |
8 - 16 |
≥32 |
≥23 |
15 - 22 |
≤14 |
Haemophilus spp.a,b |
≤4 |
8 |
≥16 |
≥20 |
17 - 19 |
≤16 |
Moraxella catarrhalisa |
≤4 |
8 |
≥16 |
- |
- |
- |
Streptococcus pneumoniae |
≤1 |
2 |
≥4 |
- |
- |
- |
a For Enterobacteriaceae, Haemophilus spp.,
and Moraxella catarrhalis, susceptibility interpretive criteria are based on a
dose of 500 mg every 12 hours in patients with normal renal function.
b Haemophilus spp. includes only isolates of H. influenzae and H.
parainfluenzae. |
Susceptibility of staphylococci to cefuroxime may be
deduced from testing only penicillin and either cefoxitin or oxacillin.
Susceptibility of Streptococcus pyogenes may be deduced
from testing penicillin.3
A report of “Susceptible” indicates that the
antimicrobial drug is likely to inhibit growth of the pathogen if the
antimicrobial drug reaches the concentration usually achievable at the site of infection.
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 a high dosage of drug can be used. This
category also provides a buffer zone that prevents small uncontrolled technical
factors from causing major discrepancies in interpretation. A report of
“Resistant” indicates that the antimicrobial drug is not likely to inhibit
growth of the pathogen if the antimicrobial drug reaches the concentrations
usually achievable at the infection site; other therapy should be selected.
Quality Control
Standardized susceptibility test procedures require the
use of laboratory controls to monitor and ensure the accuracy and precision of
supplies and reagents used in the assay, and the techniques of the individual
performing the test.1,2,4 The QC ranges for MIC and disk diffusion
testing using the 30-mcg disk are provided in Table 11.3
Table 11: Acceptable Quality Control (QC) Ranges for
Cefuroxime Axetil
QC Strain |
Minimum Inhibitory Concentrations (mcg/mL) |
Disk Diffusion Zone Diameters (mm) |
Escherichia coli ATCC 25922 |
2 to 8 |
20 to 26 |
Staphylococcus aureus ATCC 25923 |
- |
27 to 35 |
Staphylococcus aureus ATCC 29213 |
0.5 to 2 |
- |
Streptococcus pneumoniae ATCC 49619 |
0.25 to 1 |
- |
Haemophilus influenzae ATCC 49766 |
0.25 to 1 |
28 to 36 |
Neisseria gonorrhoeae ATCC 49226 |
0.25 to 1 |
33 to 41 |
ATCC = American Type Culture Collection. |
Clinical Studies
Acute Bacterial Maxillary Sinusitis
One adequate and well-controlled trial was performed in
subjects with acute bacterial maxillary sinusitis. In this trial, each subject
had a maxillary sinus aspirate collected by sinus puncture before treatment was
initiated for presumptive acute bacterial sinusitis. All subjects had radiographic
and clinical evidence of acute maxillary sinusitis. In the trial, the clinical effectiveness
of CEFTIN in treating acute maxillary sinusitis was comparable to an oral antimicrobial
agent containing a specific β-lactamase
inhibitor. However, microbiology data demonstrated CEFTIN to be effective in
treating acute bacterial maxillary sinusitis due only to Streptococcus
pneumoniae or non-β-lactamase-producing
Haemophilus influenzae. Insufficient numbers of β-lactamase-producing
Haemophilus influenzae and Moraxella catarrhalis isolates were obtained in this
trial to adequately evaluate the effectiveness of CEFTIN in treating acute bacterial
maxillary sinusitis due to these 2 organisms.
This trial randomized 317 adult subjects, 132 subjects in
the U.S. and 185 subjects in South America. Table 12 shows the results of the
intent-to-treat analysis.
Table 12: Clinical Effectiveness of CEFTIN Tablets in
the Treatment of Acute Bacterial Maxillary Sinusitis
|
U.S. Subjectsa |
South American Subjectsb |
CEFTIN 250 mg Twice Daily
(n = 49) |
Controlc
(n = 43) |
CEFTIN 250 mg Twice Daily
(n = 49) |
Controlc
(n = 43) |
Clinical success (cure + improvement) |
65% |
53% |
77% |
74% |
Clinical cure |
53% |
44% |
72% |
64% |
Clinical improvement |
12% |
9% |
5% |
10% |
a 95% confidence interval around the success
difference [-0.08, +0.32].
b 95% confidence interval around the success difference [-0.10,
+0.16].
c Control was an antibacterial drug containing a β-lactamase inhibitor. |
In this trial and in a supporting maxillary puncture
trial, 15 evaluable subjects had non- β-lactamase-producing
Haemophilus influenzae as the identified pathogen. Of these, 67% (10/15) had
this pathogen eradicated. Eighteen (18) evaluable subjects had Streptococcus pneumoniae as the identified pathogen. Of these, 83% (15/18) had this pathogen eradicated.
Early Lyme Disease
Two adequate and well-controlled trials were performed in
subjects with early Lyme disease. All subjects presented with
physician-documented erythema migrans, with or without systemic manifestations
of infection. Subjects were assessed at 1 month posttreatment for success in treating
early Lyme disease (Part I) and at 1 year posttreatment for success in
preventing the progression to the sequelae of late Lyme disease (Part II).
A total of 355 adult subjects (181 treated with
cefuroxime axetil and 174 treated with doxycycline) were randomized in the 2
trials, with diagnosis of early Lyme disease confirmed in 79% (281/355). The
clinical diagnosis of early Lyme disease in these subjects was validated by 1)
blinded expert reading of photographs, when available, of the pretreatment
erythema migrans skin lesion, and 2) serologic confirmation (using
enzyme-linked immunosorbent assay [ELISA] and immunoblot assay [“Western”
blot]) of the presence of antibodies specific to Borrelia burgdorferi, the
etiologic agent of Lyme disease. The efficacy data in Table 13 are specific to this
“validated” patient subset, while the safety data below reflect the entire
patient population for the 2 trials. Clinical data for evaluable subjects in
the “validated” patient subset are shown in Table 13.
Table 13: Clinical Effectiveness of CEFTIN Tablets
Compared with Doxycycline in the Treatment of Early Lyme Disease
|
Part I (1 Month after 20 Days of Treatment)a |
Part II (1 Year after 20 Days of Treatment)b |
CEFTIN 500 mg Twice Daily
(n = 125) |
Doxycycline 100 mg 3 Times Daily
(n = 108) |
CEFTIN 500 mg Twice Daily
(n = 105c) |
Doxycycline 100 mg 3 Times Daily
(n = 83c) |
Satisfactory clinical outcomed |
91% |
93% |
84% |
87% |
Clinical cure/success |
72% |
73% |
73% |
73% |
Clinical improvement |
19% |
19% |
10% |
13% |
a 95% confidence interval around the
satisfactory difference for Part I (-0.08, +0.05).
b 95% confidence interval around the satisfactory difference for
Part II (-0.13, +0.07).
c n's include subjects assessed as unsatisfactory clinical outcomes
(failure + recurrence) in Part I (CEFTIN - 11 [5 failure, 6 recurrence];
doxycycline - 8 [6 failure, 2 recurrence]).
d Satisfactory clinical outcome includes cure + improvement (Part I)
and success + improvement (Part II). |
CEFTIN and doxycycline were effective in prevention of
the development of sequelae of late Lyme disease.
While the incidence of drug-related gastrointestinal
adverse reactions was similar in the 2 treatment groups (cefuroxime axetil -
13%; doxycycline - 11%), the incidence of drug-related diarrhea was higher in
the cefuroxime axetil arm versus the doxycycline arm (11% versus 3%, respectively).
REFERENCES
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Methods for Antimicrobial Dilution and Disk Susceptibility Testing for
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