Amoxicillin and Clavulanate Potassium (Page 5 of 7)
Amoxicillin is a semisynthetic antibiotic with in vitro bactericidal activity against Gram-positive and Gram-negative bacteria. Amoxicillin is, however, susceptible to degradation by beta-lactamases, and therefore, the spectrum of activity does not include organisms which produce these enzymes. Clavulanic acid is a beta-lactam, structurally related to the penicillins, which possesses the ability to inactivate some beta-lactamase enzymes commonly found in microorganisms resistant to penicillins and cephalosporins. In particular, it has good activity against the clinically important plasmid-mediated beta-lactamases frequently responsible for transferred drug resistance.
The formulation of amoxicillin and clavulanic acid in Amoxicillin and Clavulanate Potassium protects amoxicillin from degradation by some beta-lactamase enzymes and extends the antibiotic spectrum of amoxicillin to include many bacteria normally resistant to amoxicillin.
Amoxicillin/clavulanic acid 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.
The following in vitro data are available, but their clinical significance is unknown. At least 90 percent of the following bacteria exhibit an in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint for amoxicillin/clavulanic acid. However, the efficacy of amoxicillin/clavulanic acid in treating clinical infections due to these bacteria has not been established in adequate and well-controlled clinical trials.
Viridans group Streptococcus
Bacteroidesspecies including Bacteroides fragilis
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.
Quantitative methods are used to determine antimicrobial minimum inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized test method2,3 (broth and/or agar). The MIC values should be interpreted according to criteria provided in Table 5.
Quantitative methods that require measurement of zone diameters can 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 method3,4. This procedure uses paper disks impregnated with 30 mcg amoxicillin/clavulanic acid (20 mcg amoxicillin plus 10 mcg clavulanic acid) to test the susceptibility of bacteria to amoxicillin/clavulanic acid. The disc diffusion interpretive criteria are provided in Table 5.
Table 5:Susceptibility Test Interpretive Criteria for Amoxicillin Clavulanic Acid
|Minimum Inhibitory Concentrations (mcg/mL)||Disk Diffusion (zone diameters in mm)|
|Haemophilus influenzae and Staphylococcus aureus||4/2||—||8/4||>20||—||≤19|
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 individuals performing the test2,3,4. Standard amoxicillin/clavulanic acid powder should provide the following range of MIC values noted in Table 6 for the diffusion technique using the 30 mcg amoxicillin/clavulanic acid (20 mcg amoxicillin plus 10 mcg clavulanic acid) disk, the criteria in Table 6 should be achieved.
Table 6: Acceptable Quality Control Ranges for Amoxicillin/Clavulanic Acid
|QC Strain||Minimum Inhibitory Concentration (mcg/mL)||Disk Diffusion(zone diameter in mm)|
|Escherichia coli ATCC 25922||2/1 to 8/4||18 to 24|
|Escherichia coli ATCC 35218||4/2 to 16/8||17 to 22|
|Haemophilus influenzae ATCC 49247||2/1 to 16/8||15 to 23|
|Staphylococcus aureus ATCC 29213||0.12/0.06 to 0.5/0.25||—|
|Staphylococcus aureus ATCC 29523||—||28 to 36|
13 NONCLINICAL TOXICOLOGY
13.1 Carcinogenesis, Mutagenesis, Impairment Of Fertility
Long‑term studies in animals have not been performed to evaluate carcinogenic potential.
Amoxicillin and Clavulanate Potassium (4:1 ratio formulation of amoxicillin:clavulanate) was non-mutagenic in the Ames bacterial mutation assay, and the yeast gene conversion assay. Amoxicillin and Clavulanate Potassium was weakly positive in the mouse lymphoma assay, but the trend toward increased mutation frequencies in this assay occurred at doses that were also associated with decreased cell survival. Amoxicillin and Clavulanate Potassium was negative in the mouse micronucleus test, and in the dominant lethal assay in mice. Potassium clavulanate alone was tested in the Ames bacterial mutation assay and in the mouse micronucleus test, and was negative in each of these assays.
Amoxicillin and Clavulanate Potassium (2:1 ratio formulation of amoxicillin:clavulanate) at oral doses of up to 1,200 mg/kg/day was found to have no effect on fertility and reproductive performance in rats. Based on body surface area, this dose of amoxicillin is approximately 4 times the maximum recommended adult human oral dose (875 mg every 12 hours). For clavulanate, the dose multiple is approximately 9 times higher than the maximum recommended adult human oral dose (125 mg every 8 hours), also based on body surface area.
14 CLINICAL STUDIES
14.1 Lower Respiratory Tract and Complicated Urinary Tract Infections
Data from 2 pivotal trials in 1,191 patients treated for either lower respiratory tract infections or complicated urinary tract infections compared a regimen of 875‑mg tablets of Amoxicillin and Clavulanate Potassium every 12 hours to 500‑mg tablets of Amoxicillin and Clavulanate Potassium dosed every 8 hours (584 and 607 patients, respectively). Comparable efficacy was demonstrated between the every 12 hours and every 8 hours dosing regimens. There was no significant difference in the percentage of adverse events in each group. The most frequently reported adverse event was diarrhea; incidence rates were similar for the 875‑mg every 12 hours and 500‑mg every 8 hours dosing regimens (15% and 14%, respectively); however, there was a statistically significant difference (p < 0.05) in rates of severe diarrhea or withdrawals with diarrhea between the regimens: 1% for 875‑mg every 12 hours regimen versus 2% for the 500‑mg every 8 hours regimen.
In one of these pivotal trials, patients with either pyelonephritis (n = 361) or a complicated urinary tract infection (i.e., patients with abnormalities of the urinary tract that predispose to relapse of bacteriuria following eradication, n = 268) were randomized (1:1) to receive either 875‑mg tablets of Amoxicillin and Clavulanate Potassium every 12 hours (n=308) or 500‑mg tablets of Amoxicillin and Clavulanate Potassium every 8 hours (n=321).
The number of bacteriologically evaluable patients was comparable between the two dosing regimens. Amoxicillin and Clavulanate Potassium produced comparable bacteriological success rates in patients assessed 2 to 4 days immediately following end of therapy. The bacteriologic efficacy rates were comparable at one of the follow‑up visits (5 to 9 days post‑therapy) and at a late post‑therapy visit (in the majority of cases, this was 2 to 4 weeks post-therapy), as seen in Table 7.
Table 7: Bacteriologic efficacy rates for Amoxicillin and Clavulanate Potassium
|Time Post Therapy||875 mg every 12 hours % (n)||500 mg every 8 hours % (n)|
|2 to 4 days||81% (58)||80% (54)|
|5 to 9 days||58% (41)||52% (52)|
|2 to 4 weeks||52% (101)||55% (104)|
As noted before, though there was no significant difference in the percentage of adverse events in each group, there was a statistically significant difference in rates of severe diarrhea or withdrawals with diarrhea between the regimens.
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