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Prescription Medications

CEFACLOR

CEFACLOR- cefaclor capsule
West-ward Pharmaceutical Corp

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

DESCRIPTION

Cefaclor is a semisynthetic cephalosporin antibiotic for oral administration. It is chemically designated as 3-chloro-7-D-(2-phenylglycinamido)-3-cephem-4-carboxylic acid monohydrate. The molecular formula for cefaclor is C15 H14 ClN3 O4 S•H2 O and the molecular weight is 385.82.

Molecular formula
(click image for full-size original)

Molecular formula

Each capsule contains cefaclor monohydrate equivalent to 250 mg (0.68 mmol) or 500 mg (1.36 mmol) anhydrous cefaclor. The capsules also contain black iron oxide, croscarmellose sodium, FD&C Red No. 3, FD&C Blue No. 2, gelatin, magnesium stearate, corn starch, and titanium dioxide.

The color of the capsule powder is white to off white.

CLINICAL PHARMACOLOGY

Cefaclor is well absorbed after oral administration to fasting subjects. Total absorption is the same whether the drug is given with or without food; however, when it is taken with food, the peak concentration achieved is 50% to 75% of that observed when the drug is administered to fasting subjects and generally appears from three fourths to 1 hour later. Following administration of 250- mg, 500-mg, and 1-g doses to fasting subjects, average peak serum levels of approximately 7, 13, and 23 mcg/mL respectively were obtained within 30 to 60 minutes. Approximately 60% to 85% of the drug is excreted unchanged in the urine within 8 hours, the greater portion being excreted within the first 2 hours. During this 8-hour period, peak urine concentrations following the 250-mg, 500-mg, and 1-g doses were approximately 600, 900, and 1,900 mcg/mL, respectively. The serum half-life in normal subjects is 0.6 to 0.9 hour. In patients with reduced renal function, the serum half-life of cefaclor is slightly prolonged. In those with complete absence of renal function, the plasma half-life of the intact molecule is 2.3 to 2.8 hours. Excretion pathways in patients with markedly impaired renal function have not been determined. Hemodialysis shortens the half-life by 25% to 30%.

Microbiology

In vitro tests demonstrate that the bactericidal action of the cephalosporins results from inhibition of cell-wall synthesis. Cefaclor 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.

Aerobes, Gram-positive
Staphylococci, including coagulase-positive, coagulase-negative, and penicillinase-producing strains
Streptococcus pneumoniae
Streptococcus pyogenes (group A β-hemolytic streptococci)

Aerobes, Gram-negative
Escherichia coli
Haemophilus influenzae , excluding β-lactamase-negative, ampicillin-resistant strains
Klebsiella spp.
Proteus mirabilis

The following in vitro data are available, but their clinical significance is unknown.

Cefaclor exhibits in vitro minimal inhibitory concentrations (MICs) of < 8 mcg/mL against most (> 90%) strains of the following microorganisms; however, the safety and effectiveness of cefaclor in treating clinical infections due to these microorganisms have not been established in adequate and well-controlled clinical trials.

Aerobes, Gram-negative
Citrobacter diversus
Moraxella (Branhamella) catarrhalis
Neisseria gonorrhoeae

Anaerobes, Gram-positive
Bacteroides spp (excluding Bacteroides fragilis)
Peptococcus
Peptostreptococcus Propionibacterium acnes

Note: Pseudomonas spp., Acinetobacter calcoaceticus and most strains of enterococci (Enterococcus faecalis , group D streptococci), Enterobacter spp., indole-positive Proteus , Morganella morganii (formerly Proteus morganii), Provendencia rettgeri (formerly Proteus rettgeri), and Serratia spp. are resistant to cefaclor. When tested by in vitro methods, staphylococci exhibit cross-resistance between cefaclor and methicillin-type antibiotics.

Susceptibility Testing

Dilution Techniques — Quantitative methods that are used to determine minimum inhibitory concentrations (MIC) provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure that has been recommended for use with cefaclor powder uses a standardized dilution method1 (broth, agar, or microdilution). The MIC values obtained should be interpreted according to the following criteria:

MIC (mcg/mL) Interpretation*
< 8 Susceptible (S)
16 Intermediate (I)
> 32 Resistant (R)

*When testing H. influenzae spp. these interpretive standards are applicable only to broth microdilution method using Haemophilus Test Medium (HTM)1

Note: β-lactamase-negative, ampicillin-resistant strains of H. influenzae should be considered resistant to cefaclor despite apparent in vitro susceptibility to this agent.

A report of “Susceptible” indicates that the pathogen is likely to be inhibited by usually achievable concentrations of the antimicrobial compound in blood. 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 usually achievable concentrations of the antimicrobial compound in the blood are unlikely to be inhibitory and that other therapy should be selected.

Standardized susceptibility test procedures require the use of laboratory control microorganisms. Standard cefaclor powder should provide the following MIC values:

Microorganism MIC (mcg/mL)
E. coli ATCC 25922 1 — 4
E. faecalis ATCC 29212 > 32
S. aureus ATCC 29213 1 — 4

When testing H. influenzae*

Microorganism MIC (mcg/mL)
H. influenzae ATCC 49766 1 — 4

*Broth microdilution test performed using Haemophilus Test Medium (HTM)1

Diffusion Techniques — Quantitative methods that require measurement of zone diameters provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure2 that has been recommended for use with disks to test the susceptibility of microorganisms to cefaclor uses the 30 mcg cefaclor disk. Interpretation involves correlation of the diameter obtained in the disk test with the MIC for cefaclor. Reports from the laboratory providing results of the standard single-disk susceptibility test with a 30 mcg cefaclor disk should be interpreted according to the following criteria:

When Testing Organisms Other Than Haemophilus spp. and Streptococci

Zone Diameter (mm) Interpretation
> 18 Susceptible (S)
15 — 17 Intermediate (I)
< 14 Resistant (R)

When testing H. influenzae *

Zone Diameter (mm) Interpretation
> 20 Susceptible (S)
17 — 19 Intermediate (I)
< 16 Resistant (R)

*Disk susceptibility test performed using Haemophilus Test Medium (HTM)2

Note: β-lactamase-negative, ampicillin-resistant strains of H. influenzae should be considered resistant to cefaclor despite apparent in vitro susceptibility to this agent.

Interpretation should be as stated above for results using dilution techniques.

As with standard dilution techniques, diffusion methods require the use of laboratory control microorganisms. The 30 mcg cefaclor disk should provide the following zone diameters in these laboratory test quality control strains:

Microorganisms Zone Diameter (mm)
E. coli ATCC 25922 23 — 27
S. aureus ATCC 25923 27 — 31

When testing H. influenzae *

Microorganisms Zone Diameter (mm)
H. influenzae ATCC 49766 25 — 31

*Disk susceptibility test performed using Haemophilus Test Medium (HTM)2

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