DESCRIPTION

CEFZIL (cefprozil) is a semi-synthetic broad-spectrum cephalosporin antibiotic.

Cefprozil is a cis and trans isomeric mixture (≥90% cis). The chemical name for the monohydrate is (6R, 7R)-7-[(R)-2-amino-2-(p-hydroxy-phenyl)acetamido]-8-oxo-3-propenyl-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid monohydrate, and the structural formula is:

Cefprozil is a white to yellowish powder with a molecular formula for the monohydrate of C18H19N3O5S•H2O and a molecular weight of 407.45.

CEFZIL tablets and CEFZIL for oral suspension are intended for oral administration.

CEFZIL tablets contain cefprozil equivalent to 250 mg or 500 mg of anhydrous cefprozil. In addition, each tablet contains the following inactive ingredients: cellulose, hypromellose, magnesium stearate, methylcellulose, simethicone, sodium starch glycolate, polyethylene glycol, polysorbate 80, sorbic acid, and titanium dioxide. The 250 mg tablets also contain FD&C Yellow No. 6.

CEFZIL for oral suspension contains cefprozil equivalent to 125 mg or 250 mg anhydrous cefprozil per 5 mL constituted suspension. In addition, the oral suspension contains the following inactive ingredients: aspartame, cellulose, citric acid, colloidal silicone dioxide, FD&C Red No. 3, flavors (natural and artificial), glycine, polysorbate 80, simethicone, sodium benzoate, sodium carboxymethylcellulose, sodium chloride, and sucrose.

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.)

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 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%-60% higher AUC and 40% lower renal clearance values compared with healthy adult volunteers 20-40 years of age. The average AUC in young and elderly female subjects was approximately 15-20% 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–12 years) and adults following oral administration of selected matched doses. The maximum concentrations are achieved at 1–2 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.

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.

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.

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:

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:

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:

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.

INDICATIONS AND USAGE

CEFZIL is indicated for the treatment of patients with mild to moderate infections caused by susceptible strains of the designated microorganisms in the conditions listed below:

UPPER RESPIRATORY TRACT

Pharyngitis/tonsillitis caused by Streptococcus pyogenes.