CLINICAL PHARMACOLOGY
Pharmacokinetics
Absorption
Oral Bioavailability
Following oral administration,
cefditoren pivoxil is absorbed from the gastrointestinal tract and hydrolyzed
to cefditoren by esterases. Maximal plasma concentrations (Cmax) of cefditoren
under fasting conditions average 1.8 ± 0.6 μg/mL following a single 200 mg
dose and occur 1.5 to 3 hours following dosing.
Less than dose-proportional
increases in Cmax and area under the concentration-time curve (AUC) were observed
at doses of 400 mg and above. Cefditoren does not accumulate in plasma
following twice daily administration to subjects with normal renal function.
Under fasting conditions, the estimated absolute bioavailability of cefditoren
pivoxil is approximately 14%. The absolute bioavailability of cefditoren
pivoxil administered with a low fat meal (693 cal, 14 g fat, 122 g carb, 23 g
protein) is 16.1 ± 3.0%.
Food Effect
Administration of cefditoren
pivoxil following a high fat meal (858 cal, 64 g fat, 43 g carb, 31 g protein)
resulted in a 70% increase in mean AUC and a 50% increase in mean Cmax compared
to administration of cefditoren pivoxil in the fasted state. After a high fat
meal, the Cmax averaged 3.1 ± 1.0 μg/mL following a single 200 mg dose of
cefditoren pivoxil and 4.4 ± 0.9 μg/mL following a 400 mg dose. Cefditoren
AUC and Cmax values from studies conducted with a moderate fat meal (648 cal,
27 g fat, 73 g carb, 29 g protein) are similar to those obtained following a
high fat meal.
Distribution
The mean volume of distribution at
steady state (Vss) of cefditoren is 9.3 ± 1.6 L. Binding of cefditoren to
plasma proteins averages 88% from in vitro determinations, and is
concentration-independent at cefditoren concentrations ranging from 0.05 to10
μg/mL. Cefditoren is primarily bound to human serum albumin and its
binding is decreased when serum albumin concentrations are reduced. Binding to
α-1acid glycoprotein ranges from 3.3 to 8.1%. Penetration into red blood
cells is negligible.
Skin blister fluid
Maximal concentrations of
cefditoren in suction-induced blister fluid were observed 4 to 6 hours
following administration of a 400 mg dose of cefditoren pivoxil with a mean of
1.1 ± 0.42 μg/mL. Mean blister fluid AUC values were 56 ± 15% of
corresponding plasma concentrations.
Tonsil tissue
In fasted patients undergoing
elective tonsillectomy, the mean concentration of cefditoren in tonsil tissue 2
to 4 hours following administration of a 200 mg dose of cefditoren pivoxil was
0.18 ± 0.07 μg/g. Mean tonsil tissue concentrations of cefditoren were 12
± 3% of the corresponding serum concentrations.
Cerebrospinal Fluid (CSF)
Data on the penetration of
cefditoren into human cerebrospinal fluid are not available.
Metabolism and Excretion
Cefditoren is eliminated from the
plasma, with a mean terminal elimination half-life (t1/2) of 1.6 ± 0.4 hours in
young healthy adults. Cefditoren is not appreciably metabolized. After
absorption, cefditoren is mainly eliminated by excretion into the urine, with a
renal clearance of approximately 4-5 L/h. Studies with the renal tubular
transport blocking agent probenecid indicate that tubular secretion, along with
glomerular filtration is involved in the renal elimination of cefditoren.
Cefditoren renal clearance is reduced in patients with renal insufficiency.
(See Special Populations, Renal Insufficiency and Hemodialysis.) Hydrolysis
of cefditoren pivoxil to its active component, cefditoren, results in the
formation of pivalate. Following multiple doses of cefditoren pivoxil, greater
than 70% of the pivalate is absorbed. Pivalate is mainly eliminated (>99%)
through renal excretion, nearly exclusively as pivaloylcarnitine. Following a
200 mg BID regimen for 10 days, the mean decrease in plasma concentrations of
total carnitine was 18.1 ± 7.2 nmole/mL, representing a 39% decrease in plasma
carnitine concentrations. Following a 400 mg BID regimen for 14 days, the mean
decrease in plasma concentrations of carnitine was 33.3 ± 9.7 nmole/mL,
representing a 63% decrease in plasma carnitine concentrations. Plasma
concentrations of carnitine returned to the normal control range within 7 to 10
days after discontinuation of cefditoren pivoxil. (See PRECAUTIONS, General
and CONTRAINDICATIONS.)
Special Populations
Geriatric
The effect of age on the
pharmacokinetics of cefditoren was evaluated in 48 male and female subjects
aged 25 to 75 years given 400 mg cefditoren pivoxil BID for 7 days.
Physiological changes related to increasing age increased the extent of
cefditoren exposure in plasma, as evidenced by a 26% higher Cmax and a 33%
higher AUC for subjects aged ≥ 65 years compared with younger subjects.
The rate of elimination of cefditoren from plasma was lower in subjects aged
≥ 65 years, with t1/2 values 16-26% longer than for younger subjects.
Renal clearance of cefditoren in subjects aged ≥ 65 years was 20-24%
lower than in younger subjects. These changes could be attributed to
age-related changes in creatinine clearance. No dose adjustments are necessary
for elderly patients with normal (for their age) renal function.
Gender
The effect of gender on the
pharmacokinetics of cefditoren was evaluated in 24 male and 24 female subjects
given 400 mg cefditoren pivoxil BID for 7 days. The extent of exposure in
plasma was greater in females than in males, as evidenced by a 14% higher Cmax and
a 16% higher AUC for females compared to males. Renal clearance of cefditoren
in females was 13% lower than in males. These differences could be attributed
to gender-related differences in lean body mass. No dose adjustments are
necessary for gender.
Renal Insufficiency
Cefditoren pharmacokinetics were
investigated in 24 adult subjects with varying degrees of renal function
following administration of cefditoren pivoxil 400 mg BID for 7 days. Decreased
creatinine clearance (CLcr) was associated with an increase in the fraction of
unbound cefditoren in plasma and a decrease in the cefditoren elimination rate,
resulting in greater systemic exposure in subjects with renal impairment. The
unbound Cmax and AUC were similar in subjects with mild renal impairment (CLcr:
50-80 mL/min/1.73 m²) compared to subjects with normal renal function (CLcr:
>80 mL/min/1.73 m²). Moderate (CLcr: 30-49 mL/min/1.73 m²) or severe (CLcr:
< 30 mL/min/1.73 m²) renal impairment increased the extent of exposure in
plasma, as evidenced by mean unbound Cmax values 90% and 114% higher and AUC
values 232% and 324% higher than that for subjects with normal renal function.
The rate of elimination from plasma was lower in subjects with moderate or
severe renal impairment, with respective mean t1/2 values of 2.7 and 4.7 hours.
No dose adjustment is necessary for patients with mild renal impairment (CLcr:
50-80 mL/min/1.73 m²). It is recommended that not more than 200 mg BID be
administered to patients with moderate renal impairment (CLcr: 30-49
mL/min/1.73 m²) and 200 mg QD be administered to patients with severe renal
impairment (CLcr: < 30 mL/min/1.73 m²). (See DOSAGE AND ADMINISTRATION.)
Hemodialysis
Cefditoren pharmacokinetics
investigated in six adult subjects with end-stage renal disease (ESRD)
undergoing hemodialysis given a single 400 mg dose of cefditoren pivoxil were
highly variable. The mean t1/2 was 4.7 hours and ranged from 1.5 to 15 hours.
Hemodialysis (4 hours duration) removed approximately 30% of cefditoren from
systemic circulation but did not change the apparent terminal elimination
half-life. The appropriate dose for ESRD patients has not been determined. (See
DOSAGE AND ADMINISTRATION.)
Hepatic Disease
Cefditoren pharmacokinetics were
evaluated in six adult subjects with mild hepatic impairment (Child-Pugh Class
A) and six with moderate hepatic impairment (Child-Pugh Class B). Following
administration of cefditoren pivoxil 400 mg BID for 7 days in these subjects,
mean Cmax and AUC values were slightly ( < 15%) greater than those observed in
normal subjects. No dose adjustments are necessary for patients with mild or
moderate hepatic impairment (Child-Pugh Class A or B). The pharmacokinetics of
cefditoren in subjects with severe hepatic impairment (Child-Pugh Class C) have
not been studied.
Microbiology
Cefditoren is a cephalosporin with
antibacterial activity against gram-positive and gram-negative pathogens. The
bactericidal activity of cefditoren results from the inhibition of cell wall
synthesis via affinity for penicillin-binding proteins (PBPs).
Cefditoren is stable in the
presence of a variety of β-lactamases, including penicillinases and some
cephalosporinases. Cefditoren has been shown to be active against most strains
of the following bacteria, both in vitro and in clinical infections, as
described in the INDICATIONS AND USAGE section.
Aerobic Gram-Positive
Microorganisms
Staphylococcus aureus (methicillin-susceptible
strains, including β-lactamase-producing strains)
Note: Cefditoren is inactive against methicillin-resistant Staphylococcus
aureus
Streptococcus pneumoniae (penicillin-susceptible
strains only) Streptococcus pyogenes
Aerobic Gram-Negative
Microorganisms
Haemophilus influenzae (including β-lactamase-producing strains)
Haemophilus parainfluenzae (including
β-lactamase-producing strains)
Moraxella catarrhalis (including
β-lactamase-producing strains)
The following in vitro data are
available, but their clinical significance is unknown . Cefditoren
exhibits in vitro minimum inhibitory concentrations (MICs) of ≤ 0.125
μg/mL against most ( ≥ 90%) strains of the following bacteria;
however, the safety and effectiveness of cefditoren in treating clinical
infections due to these bacteria have not been established in adequate and
well-controlled clinical trials.
Aerobic Gram-Positive Microorganisms
Streptococcus agalactiae
Streptococcus Groups C and G
Streptococcus, viridans group
(penicillin-susceptible and -intermediate strains)
Susceptibility Tests
Dilution Techniques
Quantitative methods that are used
to determine MICs provide reproducible estimates of the susceptibility of
bacteria to antimicrobial compounds. The MICs should be determined using a
standardized procedure. Standardized procedures are based on dilution methods1 (broth)
or equivalent with standardized inoculum concentrations and standardized
concentrations of cefditoren powder. The MIC values obtained should be
interpreted according to the following criteria:
For testing Haemophilus spp.a
and Streptococcus spp. including S. pneumoniaeb:
Clinical Isolates |
MIC (μg/mL) |
Interpretation |
S. pneumoniae |
≤ 0.125 |
Susceptible (S) |
0.250 |
Intermediate (I) |
≥ 0.50 |
Resistant (R) |
Haemophilus spp. |
≤ 0.125 |
Susceptible (S) |
0.250 |
Intermediate (I) |
≥ 0.50 |
Resistant (R) |
S. pyogenes |
≤ 0.125 |
Susceptible (S) |
aThis interpretive standard is applicable only to broth
microdilution susceptibility tests with Haemophilus spp. using Haemophilus Test Medium (HTM).1
bThese interpretive standards are applicable only to broth
microdilution susceptibility tests with Streptococcus spp. using
cation-adjusted Mueller-Hinton broth with 2-5% lysed horse blood.1 |
Susceptibility test criteria
cannot be established for S. aureus.
A report of “Susceptible”
indicates that the pathogen is likely to be inhibited if the antimicrobial
compound in the blood reaches the concentration 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 that 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 concentration usually
achievable and that other therapy should be selected. Standardized
susceptibility test procedures require the use of laboratory control bacterial
strains to control the technical aspects of the laboratory procedures. Standard
cefditoren powder should provide the following MICs with these quality control
strains:
MIC Ranges ( μg/mL) |
Microorganisms |
Streptococcus pneumoniaea ATCC 49619 |
0.016-0.12 |
Haemophilus influenzaeb ATCC 49766 |
0.004-0.016 |
Haemophilus influenzaeb ATCC 49247 |
0.06-0.25 |
aThis quality control range is applicable to only S.
pneumoniae ATCC 49619 tested by a microdilution procedure using
cation-adjusted Mueller-Hinton broth with 2-5% lysed horse blood.1
bThis quality control range is applicable to only H. influenzae ATCC 49247 and ATCC 49766 tested by a microdilution procedure using HTM.1 |
REFERENCES
1. Clinical and Laboratory Standards (CLSI). Methods for
Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically;
Approved Standard – 9th ed. CLSI document M07-A9. CLSI 950 West Valley Road.,
Suite 2500, Wayne, PA 19087, 2012.