Cefadroxil

CEFADROXIL- cefadroxil powder, for suspension
West-Ward Pharmaceutical Corp

To reduce the development of drug-resistant bacteria and maintain the effectiveness of Cefadroxil for oral suspension and other antibacterial drugs, Cefadroxil for oral suspension should be used only to treat or prevent infections that are proven or strongly suspected to be caused by bacteria.

DESCRIPTION

Cefadroxil monohydrate is a semisynthetic cephalosporin antibiotic intended for oral administration. It is a white to yellowish-white crystalline powder. It is soluble in water and it is acid-stable. It is chemically designated as 5-Thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid, 7-[[amino(4-hydroxyphenyl)acetyl]amino]-3-methyl-8-oxo-, monohydrate, [6R-[6 α (,7β ((R*)]]-. It has the formula C16H17N3O5S•H2O and the molecular weight of 381.40. It has the following structural formula:

Chemical Structure
(click image for full-size original)

Cefadroxil for oral suspension USP contains cefadroxil monohydrate USP. After reconstitution, each 5 mL contains Cefadroxil monohydrate USP equivalent to 250 mg or 500 mg of cefadroxil. In addition, cefadroxil for oral suspension USP contains the following inactive ingredients: FD&C Yellow No. 6, orange powder flavor, pineapple powder flavor, polysorbate 80, sodium benzoate, sugar (sucrose), and xanthan gum.

Cefadroxil for oral suspension, USP is off-white yellow powder, forming an orange colored suspension on constitution.

CLINICAL PHARMACOLOGY

Cefadroxil monohydrate is rapidly absorbed after oral administration. Following single doses of 500 mg and 1000 mg, average peak serum concentrations were approximately 16 and 28 mcg/mL, respectively. Measurable levels were present 12 hours after administration. Over 90% of the drug is excreted unchanged in the urine within 24 hours. Peak urine concentrations are approximately 1800 mcg/mL during the period following a single 500-mg oral dose. Increases in dosage generally produce a proportionate increase in cefadroxil monohydrate urinary concentration. The urine antibiotic concentration, following a 1-g dose, was maintained well above the MIC of susceptible urinary pathogens for 20 to 22 hours.

Microbiology

In vitro tests demonstrate that the cephalosporins are bactericidal because of their inhibition of cell-wall synthesis. Cefadroxil has been shown to be active against the following organisms both in vitro and in clinical infections (see INDICATIONS AND USAGE):

Beta-hemolytic streptococci

Staphylococci , including penicillinase-producing strains

Streptococcus (Diplococcus) pneumoniae

Escherichia coli

Proteus mirabilis

Klebsiella species

Moraxella (Branhamella) catarrhalis

Note: Most strains of Enterococcus faecalis (formerly Streptococcus faecalis) and Enterococcus faecium (formerly Streptococcus faecium) are resistant to cefadroxil monohydrate. It is not active against most strains of Enterobacter species, Morganella morganii (formerly Proteus morganii), and P. vulgaris. It has no activity against Pseudomonas species and Acinetobacter calcoaceticus (formerly Mima and Herellea species).

Susceptibility Tests

Diffusion Techniques:

The use of antibiotic disk susceptibility test methods which measure zone diameter give an accurate estimation of antibiotic susceptibility. One such standard procedure1,3 which has been recommended for use with disks to test susceptibility of organisms to cefadroxil uses the cephalosporin class (cephalothin) disk. Interpretation involves the correlation of the diameters obtained in the disk test with the minimum inhibitory concentration (MIC) for cefadroxil.

Reports from the laboratory giving results of the standard single-disk susceptibility test with a 30 mcg cephalothin disk should be interpreted according to the following criteria:

Interpretive Criteria for Enterobacteriaceae, and Staphylococcus spp.
Zone Diameter (mm) Interpretation MIC (mcg/mL)
≥18 Susceptible (S) ≤8
15 to 17 Intermediate (I) -
≤14 Resistant (R) ≥32

A report of “Susceptible” indicates that the pathogen is likely to be inhibited by generally achievable blood levels. A report of “Intermediate” suggests that the organism would be susceptible if high dosage is used or if the infection is confined to tissue and fluids (e.g., urine) in which high antibiotic levels are attained. A report of “Resistant” indicates that achievable concentrations of the antibiotic are unlikely to be inhibitory and other therapy should be selected.

Standardized procedures require the use of laboratory control organisms. The 30 mcg cephalothin disk should give the following zone diameters:

Organism Zone Diameter (mm)
Staphylococcus aureus ATCC 25923 29 to 37
Escherichia coli ATCC 25922 17 to 21

Dilution Techniques:

When using the CLSI agar dilution or broth dilution (including microdilution) method2, 3 or equivalent, the MIC values should be interpreted according to the following criteria:

Interpretive Criteria for Enterobacteriaceae, and Staphylococcus spp.
MIC (mcg/mL) Interpretation
≤8 Susceptible (S)
16 Intermediate (I)
≥32 Resistant (R)

As with standard diffusion methods, dilution procedures require the use of laboratory control organisms. Standard cephalothin powder should provide the following MIC values:

Microorganism MIC (mcg/mL)
Escherichia coli ATCC 25922 4 to 16
Staphylococcus aureus ATCC 29213 0.12 to 0.5
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