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CLINICAL PHARMACOLOGY

Absorption and Excretion

Cefpodoxime proxetil is a prodrug that is absorbed from the gastrointestinal tract and deesterified to its active metabolite, cefpodoxime. Following oral administration of 100 mg of cefpodoxime proxetil to fasting subjects, approximately 50% of the administered cefpodoxime dose was absorbed systemically. Over the recommended dosing range (100 to 400 mg), approximately 29 to 33% of the administered cefpodoxime dose was excreted unchanged in the urine in 12 hours. There is minimal metabolism of cefpodoxime in vivo.

Effects of Food

The extent of absorption (mean AUC) and the mean peak plasma concentration increased when film-coated tablets were administered with food. Following a 200 mg tablet dose taken with food, the AUC was 21 to 33% higher than under fasting conditions, and the peak plasma concentration averaged 3.1 mcg/mL in fed subjects versus 2.6 mcg/mL in fasted subjects. Time to peak concentration was not significantly different between fed and fasted subjects.

When a 200 mg dose of the suspension was taken with food, the extent of absorption (mean AUC) and mean peak plasma concentration in fed subjects were not significantly different from fasted subjects, but the rate of absorption was slower with food (48% increase in Tmax).

Pharmacokinetics of Cefpodoxime Proxetil Film-coated Tablets

Over the recommended dosing range (100 to 400 mg), the rate and extent of cefpodoxime absorption exhibited dose-dependency; dose-normalized Cmax and AUC decreased by up to 32% with increasing dose. Over the recommended dosing range, the Tmax was approximately 2 to 3 hours and the T½ ranged from 2.09 to 2.84 hours. Mean Cmax was 1.4 mcg/mL for the 100 mg dose, 2.3 mcg/mL for the 200 mg dose, and 3.9 mcg/mL for the 400 mg dose. In patients with normal renal function, neither accumulation nor significant changes in other pharmacokinetic parameters were noted following multiple oral doses of up to 400 mg Q 12 hours.

CEFPODOXIME PLASMA LEVELS (mcg/mL) IN FASTED ADULTS AFTER FILM-COATED TABLET ADMINISTRATION (Single Dose)

Dose (cefpodoxime equivalents) Time after oral ingestion
1hr 2hr 3hr 4hr 6hr 8hr 12hr
100 mg 0.98 1.4 1.3 1.0 0.59 0.29 0.08
200 mg 1.5 2.2 2.2 1.8 1.2 0.62 0.18
400 mg 2.2 3.7 3.8 3.3 2.3 1.3 0.38

Pharmacokinetics of Cefpodoxime Proxetil Suspension

In adult subjects, a 100 mg dose of oral suspension produced an average peak cefpodoxime concentration of approximately 1.5 mcg/mL (range: 1.1 to 2.1 mcg/mL), which is equivalent to that reported following administration of the 100 mg tablet. Time to peak plasma concentration and area under the plasma concentration-time curve (AUC) for the oral suspension were also equivalent to those produced with film-coated tablets in adults following a 100 mg oral dose.

The pharmacokinetics of cefpodoxime were investigated in 29 patients aged 1 to 17 years. Each patient received a single, oral, 5 mg/kg dose of cefpodoxime oral suspension. Plasma and urine samples were collected for 12 hours after dosing. The plasma levels reported from this study are as follows:

CEFPODOXIME PLASMA LEVELS (mcg/mL) IN FASTED PATIENTS (1 to 17 YEARS OF AGE) AFTER SUSPENSION ADMINISTRATION

Dose (cefpodoxime equivalents) Time after oral ingestion
1hr 2hr 3hr 4hr 6hr 8hr 12hr
5 mg/kg1 1.4 2.1 2.1 1.7 0.90 0.40 0.090
1Dose did not exceed 200 mg.

Distribution

Protein binding of cefpodoxime ranges from 22 to 33% in serum and from 21 to 29% in plasma.

Skin Blister

Following multiple-dose administration every 12 hours for 5 days of 200 mg or 400 mg cefpodoxime proxetil, the mean maximum cefpodoxime concentration in skin blister fluid averaged 1.6 and 2.8 mcg/mL, respectively. Skin blister fluid cefpodoxime levels at 12 hours after dosing averaged 0.2 and 0.4 mcg/mL for the 200 mg and 400 mg multiple-dose regimens, respectively.

Tonsil Tissue

Following a single, oral 100 mg cefpodoxime proxetil film-coated tablet, the mean maximum cefpodoxime concentration in tonsil tissue averaged 0.24 mcg/g at 4 hours post-dosing and 0.09 mcg/g at 7 hours post-dosing. Equilibrium was achieved between plasma and tonsil tissue within 4 hours of dosing. No detection of cefpodoxime in tonsillar tissue was reported 12 hours after dosing. These results demonstrated that concentrations of cefpodoxime exceeded the MIC90 of S. pyogenes for at least 7 hours after dosing of 100 mg of cefpodoxime proxetil.

Lung Tissue

Following a single, oral 200 mg cefpodoxime proxetil film-coated tablet, the mean maximum cefpodoxime concentration in lung tissue averaged 0.63 mcg/g at 3 hours post-dosing, 0.52 mcg/g at 6 hours post-dosing, and 0.19 mcg/g at 12 hours post-dosing. The results of this study indicated that cefpodoxime penetrated into lung tissue and produced sustained drug concentrations for at least 12 hours after dosing at levels that exceeded the MIC90 for S. pneumoniae and H. influenzae.

CSF

Adequate data on CSF levels of cefpodoxime are not available.

Effects of Decreased Renal Function

Elimination of cefpodoxime is reduced in patients with moderate to severe renal impairment ( < 50 mL/min creatinine clearance). (See PRECAUTIONS and DOSAGE AND ADMINISTRATION.) In subjects with mild impairment of renal function (50 to 80 mL/min creatinine clearance), the average plasma half-life of cefpodoxime was 3.5 hours. In subjects with moderate (30 to 49 mL/min creatinine clearance) or severe renal impairment (5 to 29 mL/min creatinine clearance), the half-life increased to 5.9 and 9.8 hours, respectively. Approximately 23% of the administered dose was cleared from the body during a standard 3-hour hemodialysis procedure.

Effect of Hepatic Impairment (cirrhosis)

Absorption was somewhat diminished and elimination unchanged in patients with cirrhosis. The mean cefpodoxime T½ and renal clearance in cirrhotic patients were similar to those derived in studies of healthy subjects. Ascites did not appear to affect values in cirrhotic subjects. No dosage adjustment is recommended in this patient population.

Pharmacokinetics in Elderly Subjects

Elderly subjects do not require dosage adjustments unless they have diminished renal function. (See PRECAUTIONS.) In healthy geriatric subjects, cefpodoxime half-life in plasma averaged 4.2 hours (vs 3.3 in younger subjects) and urinary recovery averaged 21% after a 400 mg dose was administered every 12 hours. Other pharmacokinetic parameters (Cmax, AUC, and Tmax) were unchanged relative to those observed in healthy young subjects.

Microbiology

Mechanism of Action

Cefpodoxime is a bactericidal agent that acts by inhibition of bacterial cell wall synthesis. Cefpodoxime has activity in the presence of some beta-lactamases, both penicillinases and cephalosporinases, of Gram-negative and Gram-positive bacteria.

Mechanism of Resistance

Resistance to Cefpodoxime is primarily through hydrolysis by beta-lactamase, alteration of penicillin-binding proteins (PBPs), and decreased permeability.

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

Gram-positive bacteria

Staphylococcus aureus (methicillin-susceptible strains, including those producing penicillinases)
Staphylococcus saprophyticus

Streptococcus pneumoniae
(excluding penicillin-resistant isolates)
Streptococcus pyogenes

Gram-negative bacteria

Escherichia coli
Klebsiella pneumoniae

Proteus mirabilis

Haemophilus influenzae
(including beta-lactamase producing isolates)
Moraxella catarrhalis

Neisseria gonorrhoeae
(including penicillinase-producing isolates)

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 Cefpodoxime. However, the efficacy of Cefpodoxime in treating clinical infections due to these microorganisms has not been established in adequate and well-controlled clinical trials.

Gram-positive bacteria

Streptococcus agalactiae
Streptococcus spp
. (Groups C, F, G)

Gram-negative bacteria

Citrobacter diversus
Klebsiella oxytoca

Proteus vulgaris

Providencia rettgeri

Haemophilus parainfluenzae

Anaerobic Gram-positive bacteria

Peptostreptococcus magnus

Susceptibility Test Methods

When available, the clinical microbiology laboratory should provide the results of in vitro susceptibility test results for antimicrobial drug products used in resident hospitals 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 minimal inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized test method1,3. The MIC values should be interpreted according to criteria provided in Table 1.

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 method2,3. This procedure uses paper disks impregnated with 10 mcg Cefpodoxime to test the susceptibility of microorganisms to Cefpodoxime. The disk diffusion interpretive criteria are provided in Table 1.

Table 1: Susceptibility Test Interpretive Criteria for Cefpodoxime2

Pathogen Minimum Inhibitory Concentrations (mcg/ml) Disk Diffusion Diameters (mm)
S I R S I R
Enterobacteriaceae ≤ 2 4 ≥ 8 ≥ 21 18-20 ≤ 17
Haemophilus influenzaea ≤ 2 - - ≥ 21 - -
Streptococcus pneumoniae ≤ 0.5 1 ≥ 2 - - -
Neisseria gonorrhoeaea ≤ 0.5 - - >29 - -
Susceptibility of staphylococci to Cefpodoxime may be deduced from testing only penicillin and either cefoxitin or oxacillin.
aThe current absence of resistant isolates precludes defining any results other than “Susceptible.” Isolates yielding MIC results other than “Susceptible” should be submitted to a reference laboratory for further testing.

A report of Susceptible indicates that the antimicrobial is likely to inhibit growth of the pathogen if the antimicrobial compound reaches the concentration at the infection site necessary to inhibit growth of the pathogen. 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 is not likely to inhibit growth of the pathogen if the antimicrobial compound 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 test1,2,3. Standard Cefpodoxime powder should provide the following range of MIC values noted in Table 2. For the diffusion technique using the 10 mcg disk, the criteria in Table 2 should be achieved.

Table 2: Acceptable Quality Control Ranges for Cefpodoxime

QC Strains Minimum Inhibitory Concentrations (mcg/mL) Disk Diffusion Zone diameters (mm)
Escherichia coli ATCC 25922 0.25 - 1 8 2 - 3 2
Haemophilus influenzae ATCC 49247 0.25-1 3 - 5 2
Streptococcus pneumoniae ATCC 49619 0.03-0.12 4 3 - 8 2
Neisseria gonorrhoeae ATCC 49226 0.03 -0.12 3 4 - 5 3
Staphylococcus aureus ATCC 25923 - 19 - 25
Staphylococcus aureus ATCC 29213 1 - 8 -

Clinical Trials

Cystitis

In two double-blind, 2:1 randomized, comparative trials performed in adults in the United States, cefpodoxime proxetil was compared to other beta-lactam antibiotics. In these studies, the following bacterial eradication rates were obtained at 5 to 9 days after therapy:

Pathogen Cefpodoxime Comparator
E. coli 200/243 (82%) 99/123 (80%)
Other pathogens 34/42 (81%) 23/28 (82%)
K. pneumoniae    
P. mirabilis    
S. saprophyticus    
TOTAL 234/285 (82%) 122/151 (81%)

In these studies, clinical cure rates and bacterial eradication rates for cefpodoxime proxetil were comparable to the comparator agents; however, the clinical cure rates and bacteriologic eradication rates were lower than those observed with some other classes of approved agents for cystitis.

Acute Otitis Media Studies

Pathogen Cefpodoxime Proxetil Cefixime
5 mg/kg Q 12 h x 5 d
S. pneumoniae 88/122 (72%) 72/124 (58%)
H. influenzae 50/76 (66%) 61/81 (75%)
M. catarrhalis 22/39 (56%) 23/41 (56%)
S. pyogenes 20/25 (80%) 13/23 (57%)
Clinical succes rate 171/254 (67%) 165/258 (64%)

In controlled studies of acute otitis media performed in the United States, where significant rates of beta-lactamase-producing organisms were found, cefpodoxime proxetil was compared to cefixime. In these studies, using very strict evaluability criteria and microbiologic and clinical response criteria at the 4 to 21 day post-therapy follow-up, the following presumptive bacterial eradication/clinical success outcomes (cured and improved) were obtained.

REFERENCES

1. Clinical and Laboratory Standards Institute (CLSI). Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically; Approved Standard - Ninth Edition. CLSI document M07-A9, Clinical and Laboratory Standards Institute, 950 West Valley Road, Suite 2500, Wayne, Pennsylvania 19087, USA, 2012.

2. Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Susceptibility Testing; Twenty-third Informational Supplement, CLSI document M100-S23. CLSI document M100-S23, Clinical and Laboratory Standards Institute, 950 West Valley Road, Suite 2500, Wayne, Pennsylvania 19087, USA, 2013.

3. Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Disk Diffusion Susceptibility Tests; Approved Standard – Eleventh Edition CLSI document M02-A11, Clinical and Laboratory Standards Institute, 950 West Valley Road, Suite 2500, Wayne, Pennsylvania 19087, USA, 2012.

Last reviewed on RxList: 7/8/2013
This monograph has been modified to include the generic and brand name in many instances.

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