Augmentin

[Amoxicillin/Clavulanate]

A report of "Susceptible" indicates that the pathogen is likely to be inhibited if the antimicrobial compound in the blood reaches the concentration 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 amoxicillin/ clavulanate potassium powder should provide the following MIC values: Microorganism MIC Range (µg/ mL) **
Escherichia coli ATCC 25922 2 to 8 Escherichia coli ATCC 35218 4 to 16
Enterococcus faecalis ATCC 29212 0.25 to 1.0 Haemophilus influenzae ATCC 49247 2 to 16
Staphylococcus aureus ATCC 29213 0.12 to 0.5 Streptococcus pneumoniae ATCC 49619 0.03 to 0.12
** Expressed as concentration of amoxicillin in the presence of clavulanic acid at a constant 2 parts amoxicillin to 1 part clavulanic acid.
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 procedure 2 requires the use of standardized inoculum concentrations. This procedure uses paper disks impregnated with 30 µg of amoxicillin/ clavulanate potassium (20 µg amoxicillin plus 10 µg clavulanate potassium) to test the susceptibility of microorganisms to amoxicillin/ clavulanic acid.

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Reports from the laboratory providing results of the standard single-disk susceptibility test with a 30 µg amoxicillin/ clavulanate acid (20 µg amoxicillin plus 10 µg clavulanate potassium) disk should be interpreted according to the following criteria:
RECOMMENDED RANGES FOR AMOXICILLIN/ CLAVULANIC ACID SUSCEPTIBILITY TESTING

For Staphylococcus ** species and H. influenzae a : Zone Diameter (mm) Interpretation
. 20 Susceptible (S) . 19 Resistant (R)
For other organisms except S. pneumoniae b and N. gonorrhoeae c : Zone Diameter (mm) Interpretation
. 18 Susceptible (S) 14 to 17 Intermediate (I)
. 13 Resistant (R) ** Staphylococci which are resistant to methicillin/ oxacillin must be considered as resistant to amoxicillin/ clavulanic acid.

a A broth microdilution method should be used for testing H. influenzae. Beta-lactamase negative, ampicillin-resistant strains must be considered resistant to amoxicillin/ clavulanic acid.

b Susceptibility of S. pneumoniae should be determined using a 1 µg oxacillin disk. Isolates with oxacillin zone sizes of . 20 mm are susceptible to amoxicillin/ clavulanic acid. An amoxicillin/ clavulanic acid MIC should be determined on isolates of S. pneumoniae with oxacillin zone sizes of . 19 mm.

c A broth microdilution method should be used for testing N. gonorrhoeae and interpreted according to penicillin breakpoints. 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 amoxicillin/ clavulanic acid.

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 amoxicillin/ clavulanate potassium (20 µg amoxicillin plus 10 µg clavulanate potassium) disk should provide the following zone diameters in these laboratory quality control strains: Microorganism Zone Diameter (mm)
Escherichia coli ATCC 25922 19 to 25
Escherichia coli ATCC 35218 18 to 22
Staphylococcus aureus ATCC 25923 28 to 36

INDICATIONS AND USAGE

Augmentin is indicated in the treatment of infections caused by susceptible strains of the designated organisms in the conditions listed below:

Lower Respiratory Tract Infections– caused by -lactamase-producing strains of Haemophilus influenzae and Moraxella (Branhamella) catarrhalis.

Otitis Media– caused by -lactamase-producing strains of Haemophilus influenzae and Moraxella (Branhamella) catarrhalis.

Sinusitis– caused by -lactamase-producing strains of Haemophilus influenzae and Moraxella (Branhamella) catarrhalis.

Skin and Skin Structure Infections– caused by -lactamase-producing strains of Staphylococcus aureus, Escherichia coli and Klebsiella spp.

Urinary Tract Infections– caused by -lactamase-producing strains of Escherichia coli, Klebsiella spp. and Enterobacter spp.

While Augmentin is indicated only for the conditions listed above, infections caused by ampicillin-susceptible organisms are also amenable to Augmentin treatment due to its amoxicillin content. Therefore, mixed infections caused by ampicillin-susceptible organisms and -lactamase-producing organisms susceptible to Augmentin should not require the addition of another antibiotic.

Because amoxicillin has greater in vitro activity against Streptococcus pneumoniae than does ampicillin or penicillin, the majority of S. pneumoniae strains with intermediate susceptibility to ampicillin or penicillin are fully susceptible to amoxicillin and Augmentin. (See Microbiology subsection.)

Bacteriological studies, to determine the causative organisms and their susceptibility to Augmentin, should be performed together with any indicated surgical procedures. Therapy may be instituted prior to obtaining the results from bacteriological and susceptibility studies to determine the causative organisms and their susceptibility to Augmentin when there is reason to believe the infection may involve any of the -lactamase-producing organisms listed above. Once the results are known, therapy should be adjusted, if appropriate.

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