CLINICAL PHARMACOLOGY
The pharmacokinetic data were derived from the capsule formulation; however, bioequivalence has been demonstrated for the oral solution, capsule, tablet, and suspension formulations under fasting conditions.
Following oral administration of cefprozil to fasting subjects, approximately 95% of the dose was absorbed. The average plasma half-life in normal subjects was 1.3 hours, while the steady-state volume of distribution was estimated to be 0.23 L/kg. The total body clearance and renal clearance rates were approximately 3 mL/min/kg and 2.3 mL/min/kg, respectively.
Average peak plasma concentrations after administration of 250 mg, 500 mg, or 1 g doses of cefprozil to fasting subjects were approximately 6.1, 10.5, and 18.3 µg/mL, respectively, and were obtained within 1.5 hours after dosing. Urinary recovery accounted for approximately 60% of the administered dose. (See Table.)
Dosage (mg) |
Mean Plasma Cefprozil
Concentrations (µg/mL)* |
8-hour Urinary
Excretion (%) |
|
Peak appx. 1.5 h |
4 h |
8 h |
|
250 mg |
6.1 |
1.7 |
0.2 |
60% |
500 mg |
10.5 |
3.2 |
0.4 |
62% |
1000 mg |
18.3 |
8.4 |
1.0 |
54% |
*Data represent mean values of 12 healthy
volunteers. |
During the first 4-hour period after drug administration, the average urine concentrations following 250 mg, 500 mg, and 1 g doses were approximately 700 µg/mL, 1000 µg/mL, and 2900 µg /mL, respectively.
Administration of CEFZIL (cefprozil) tablet or suspension formulation with food did not affect the extent of absorption (AUC) or the peak plasma concentration (Cmax) of cefprozil. However, there was an increase of 0.25 to 0.75 hours in the time to maximum plasma concentration of cefprozil (Tmax).
The bioavailability of the capsule formulation of cefprozil was not affected when administered 5 minutes following an antacid.
Plasma protein binding is approximately 36% and is independent of concentration in the range of 2 µg/mL to 20 µg/mL.
There was no evidence of accumulation of cefprozil in the plasma in individuals with normal renal function following multiple oral doses of up to 1000 mg every 8 hours for 10 days.
In patients with reduced renal function, the plasma half-life may be prolonged
up to 5.2 hours depending on the degree of the renal dysfunction. In patients
with complete absence of renal function, the plasma half-life of cefprozil has
been shown to be as long as 5.9 hours. The half-life is shortened during hemodialysis.
Excretion pathways in patients with markedly impaired renal function have not
been determined. (See PRECAUTIONS and DOSAGE
AND ADMINISTRATION.)
In patients with impaired hepatic function, the half-life increases to approximately 2 hours. The magnitude of the changes does not warrant a dosage adjustment for patients with impaired hepatic function.
Healthy geriatric volunteers ( ≥ 65 years old) who received a single 1-g dose of cefprozil had 35% to 60% higher AUC and 40% lower renal clearance values compared with healthy adult volunteers 20 to 40 years of age. The average AUC in young and elderly female subjects was approximately 15% to 20% higher than in young and elderly male subjects. The magnitude of these age- and gender-related changes in the pharmacokinetics of cefprozil is not sufficient to necessitate dosage adjustments.
Adequate data on CSF levels of cefprozil are not available.
Comparable pharmacokinetic parameters of cefprozil are observed between pediatric
patients (6 months to 12 years) and adults following oral administration of
selected matched doses. The maximum concentrations are achieved at 1 to 2 hours
after dosing. The plasma elimination half-life is approximately 1.5 hours. In
general, the observed plasma concentrations of cefprozil in pediatric patients
at the 7.5, 15, and 30 mg/kg doses are similar to those observed within the
same time frame in normal adult subjects at the 250, 500, and 1000 mg doses,
respectively. The comparative plasma concentrations of cefprozil in pediatric
patients and adult subjects at the equivalent dose level are presented in the
table below.
|
Mean (SD) Plasma Cefprozil Concentrations
(µg/mL) |
|
Population |
Dose |
1 h |
2 h |
4 h |
6 h |
T1/2 (h) |
children (n=18) |
7.5 mg/kg |
4.70 (1.57) |
3.99 (1.24) |
0.91 (0.30) |
0.23a
(0.13) |
0.94 (0.32) |
adults (n=12) |
250 mg |
4.82 (2.13) |
4.92 (1.13) |
1.70b (0.53) |
0.53
(0.17) |
1.28 (0.34) |
children (n=19) |
15 mg/kg |
10.86 (2.55) |
8.47 (2.03) |
2.75 (1.07) |
0.61c (0.27) |
1.24 (0.43) |
adults (n=12) |
500 mg |
8.39 (1.95) |
9.42 (0.98) |
3.18d (0.76) |
1.00d (0.24) |
1.29 (0.14) |
children (n=10) |
30 mg/kg |
16.69 (4.26) |
17.61 (6.39) |
8.66 (2.70) |
- |
2.06 (0.21) |
adults (n=12) |
1000 mg |
11.99 (4.67) |
16.95 (4.07) |
8.36 (4.13) |
2.79
(1.77) |
1.27 (0.12) |
an=11; bn=5; cn
=9; dn=11. |
Microbiology
Cefprozil has in vitro activity against a broad range of gram-positive
and gram-negative bacteria. The bactericidal action of cefprozil results from
inhibition of cell-wall synthesis. Cefprozil has been shown to be active against
most strains of the following microorganisms both in vitro and in clinical
infections as described in the INDICATIONS AND USAGE section.
Aerobic gram-positive microorganisms:
Staphylococcus aureus (including β-lactamase-producing strains)
NOTE: Cefprozil is inactive against methicillin-resistant staphylococci.
Streptococcus pneumoniae
Streptococcus pyogenes |
Aerobic gram-negative microorganisms:
Haemophilus influenzae (including β-lactamase-producing strains)
Moraxella (Branhamella) catarrhalis (including β-lactamase-producing
strains) |
The following in vitro data are available; however, their clinical significance
is unknown. Cefprozil exhibits in vitro minimum inhibitory concentrations
(MICs) of 8 µg/mL or less against most ( ≥ 90%) strains of the following microorganisms;
however, the safety and effectiveness of cefprozil in treating clinical infections
due to these microorganisms have not been established in adequate and well-controlled
clinical trials.
Aerobic gram-positive microorganisms: |
Enterococcus durans
Enterococcus faecalis
Listeria monocytogenes
Staphylococcus epidermidis
Staphylococcus saprophyticus |
Staphylococcus warneri
Streptococcus agalactiae
Streptococci (Groups C, D, F, and G)
viridans group Streptococci |
NOTE: Cefprozil is inactive against Enterococcus faecium. |
Aerobic gram-negative microorganisms: |
Citrobacter diversus
Escherichia coli
Klebsiella pneumoniae
Neisseria gonorrhoeae (including β-lactamase-producing strains) |
Proteus mirabilis
Salmonella spp.
Shigellaspp.
Vibriospp. |
NOTE: Cefprozil is inactive against most strains of
Acinetobacter, Enterobacter, Morganella morganii, Proteus vulgaris, Providencia,
Pseudomonas, and Serratia. |
Anaerobic microorganisms: |
Prevotella (Bacteroides) melaninogenicus
Clostridium difficile
Clostridium perfringens |
Fusobacterium spp. Peptostreptococcus spp. Propionibacterium
acnes |
NOTE: Most strains of the Bacteroides fragilis
group are resistant to cefprozil. |
Susceptibility Tests
Dilution Techniques: Quantitative methods are used to determine antimicrobial
minimal 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
method1,2 (broth or agar) or equivalent with standardized inoculum
concentrations and standardized concentrations of cefprozil powder. The MIC
values should be interpreted according to the following criteria:
MIC (µg/mL) |
Interpretation |
≤ 8 |
Susceptible (S) |
16 |
Intermediate (I) |
≥ 32 |
Resistant (R) |
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. Standard cefprozil powder should provide the following MIC values:
Microorganism |
MIC (µg/mL) |
Enterococcus faecalis ATCC 29212 |
4-16 |
Escherichia coli ATCC 25922 |
1-4 |
Haemophilus influenzae ATCC 49766 |
1-4 |
Staphylococcus aureus ATCC 29213 |
0.25-1 |
Streptococcus pneumoniae ATCC 49619 |
0.25-1 |
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 procedure3
requires the use of standardized inoculum concentrations. This procedure uses
paper disks impregnated with 30 µg cefprozil to test the susceptibility of microorganisms
to cefprozil.
Reports from the laboratory providing results of the standard single-disk susceptibility test with a 30-µg cefprozil disk should be interpreted according to the following criteria:
Zone diameter (mm) |
Interpretation |
≥ 18 |
Susceptible (S) |
15-17 |
Intermediate (I) |
≤ 14 |
Resistant (R) |
Interpretation should be as stated above for results using dilution techniques. Interpretation involves correlation of the diameter obtained in the disk test with the MIC for cefprozil.
As with standardized dilution techniques, diffusion methods require the use of laboratory control microorganisms that are used to control the technical aspects of the laboratory procedures. For the diffusion technique, the 30-µg cefprozil disk should provide the following zone diameters in these laboratory test quality control strains.
Microorganism |
Zone diameter (mm) |
Escherichia coli ATCC 25922 |
21-27 |
Haemophilus influenzae ATCC 49766 |
20-27 |
Staphylococcus aureus ATCC 25923 |
27-33 |
Streptococcus pneumoniae ATCC 49619 |
25-32 |
Clinical Studies
Study One
In a controlled clinical study of acute otitis media performed in the
United States where significant rates of β-lactamase-producing organisms
were found, cefprozil was compared to an oral antimicrobial agent that contained
a specific β-lactamase inhibitor. In this study, using very strict evaluability
criteria and microbiologic and clinical response criteria at the 10 to 16 days
post-therapy follow-up, the following presumptive bacterial eradication/clinical
cure outcomes (ie, clinical success) and safety results were obtained:
U.S. Acute Otitis Media Study Cefprozil vs β-lactamase
inhibitor-containing control drug
EFFICACY: |
Pathogen |
% of Cases with Pathogen
(n=155) |
Outcome |
S. pneumoniae |
48.4% |
cefprozil success rate 5% better than control |
H. influenzae |
35.5% |
cefprozil success rate 17% less than control |
M. catarrhalis |
13.5% |
cefprozil success rate 12% less than control |
S. pyogenes |
2.6% |
cefprozil equivalent to control |
Overall |
100.0% |
cefprozil success rate 5% less than control |
Safety
The incidences of adverse events, primarily diarrhea and rash*, were clinically and statistically significantly higher in the control arm versus the cefprozil arm.
Age Group |
Cefprozil |
Control |
6 months-2 years |
21% |
41% |
3-12 years |
10% |
19% |
*The majority of these involved the diaper
area in young children. |
Study Two
In a controlled clinical study of acute otitis media performed in Europe,
cefprozil was compared to an oral antimicrobial agent that contained a specific
β-lactamase inhibitor. As expected in a European population, this study
population had a lower incidence of β-lactamase-producing organisms than
usually seen in U.S. trials. In this study, using very strict evaluability criteria
and microbiologic and clinical response criteria at the 10 to 16 days post-therapy
follow-up, the following presumptive bacterial eradication/clinical cure outcomes
(ie, clinical success) were obtained:
European Acute Otitis Media Study Cefprozil vs β-lactamase
inhibitor-containing control drug
EFFICACY |
Pathogen |
% of Cases with Pathogen (n=47) |
Outcome |
S. pneumoniae |
51.0% |
cefprozil equivalent to control |
H. influenzae |
29.8% |
cefprozil equivalent to control |
M. catarrhalis |
6.4% |
cefprozil equivalent to control |
S. pyogenes |
12.8% |
cefprozil equivalent to control |
Overall |
100.0% |
cefprozil equivalent to control |
Safety
The incidence of adverse events in the cefprozil arm was comparable to the
incidence of adverse events in the control arm (agent that contained a specific
β-lactamase inhibitor).
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. Methods
for Antimicrobial Susceptibility Testing of Anaerobic Bacteria-Third Edition.
Approved Standard NCCLS Document M11-A3, Vol. 13, No. 26, NCCLS, Villanova,
PA, December 1993.
3. 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.