Amoxicillin and Clavulanate Potassium (Page 4 of 5)

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Amoxicillin and Clavulanate Potassium is an antibacterial drug. [see Microbiology 12.4]

12.3 Pharmacokinetics

Mean amoxicillin and clavulanate potassium pharmacokinetic parameters in normal adults following administration of Amoxicillin and Clavulanate Potassium Tablets are shown in Table 3 and following administration of Amoxicillin and Clavulanate Potassium Powder for Oral Suspension and Chewable Tablets are shown in Table 4.


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Oral administration of 5 mL of 250 mg/5 mL suspension of Amoxicillin and Clavulanate Potassium or the equivalent dose of 10 mL of 125 mg/5 mL suspension of Amoxicillin and Clavulanate Potassium provides average peak serum concentrations approximately 1 hour after dosing of 6.9 mcg/mL for amoxicillin and 1.6 mcg/mL for clavulanic acid. The areas under the serum concentration curves obtained during the first 4 hours after dosing were 12.6 mcg*h/mL for amoxicillin and 2.9 mcg*h/mL for clavulanic acid when 5 mL of 250 mg/5 mL suspension of Amoxicillin and Clavulanate Potassium or equivalent dose of 10 mL of 125 mg/5 mL suspension of Amoxicillin and Clavulanate Potassium were administered to normal adults. One 250 mg chewable tablet of Amoxicillin and Clavulanate Potassium or two 125 mg chewable tablets of Amoxicillin and Clavulanate Potassium are equivalent to 5 mL of 250 mg/5 mL suspension of Amoxicillin and Clavulanate Potassium and provide similar serum concentrations of amoxicillin and clavulanic acid.

Amoxicillin serum concentrations achieved with Amoxicillin and Clavulanate Potassium are similar to those produced by the oral administration of equivalent doses of amoxicillin alone. Time above the minimum inhibitory concentration of 1 mcg/mL for amoxicillin has been shown to be similar after corresponding every 12 hour and every 8 hour dosing regimens of Amoxicillin and Clavulanate Potassium in adults and children.

Absorption: Dosing in the fasted or fed state has minimal effect on the pharmacokinetics of amoxicillin. While Amoxicillin and Clavulanate Potassium can be given without regard to meals, absorption of clavulanate potassium when taken with food is greater relative to the fasted state. In one study, the relative bioavailability of clavulanate was reduced when Amoxicillin and Clavulanate Potassium was dosed at 30 and 150 minutes after the start of a high‑fat breakfast.

Distribution: Neither component in Amoxicillin and Clavulanate Potassium is highly protein‑bound; clavulanic acid is approximately 25% bound to human serum and amoxicillin approximately 18% bound.

Amoxicillin diffuses readily into most body tissues and fluids with the exception of the brain and spinal fluid.

Two hours after oral administration of a single 35 mg/kg dose of suspension of Amoxicillin and Clavulanate Potassium to fasting children, average concentrations of 3 mcg/mL of amoxicillin and 0.5 mcg/mL of clavulanic acid were detected in middle ear effusions.

Metabolism and Excretion: The half‑life of amoxicillin after the oral administration of Amoxicillin and Clavulanate Potassium is 1.3 hours and that of clavulanic acid is 1 hour.

Approximately 50% to 70% of the amoxicillin and approximately 25% to 40% of the clavulanic acid are excreted unchanged in urine during the first 6 hours after administration of a single 250 mg or 500 mg tablet of Amoxicillin and Clavulanate Potassium.

12.4 Microbiology

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.

Gram-positive bacteria

Staphylococcus aureus

Gram-negative bacteria

Enterobacter species

Escherichia coli

Haemophilus influenzae

Klebsiella species

Moraxella catarrhalis

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.

Gram-positive bacteria

Enterococcus faecalis

Staphylococcus epidermidis

Staphylococcus saprophyticus

Streptococcus pneumoniae

Streptococcus pyogenes

Viridans group Streptococcus

Gram-negative Bacteria

Eikenellacorrodens

Proteus mirabilis

Anaerobic Bacteria

Bacteroidesspecies including Bacteroides fragilis

Fusobacterium species

Peptostreptococcus species

Susceptibility Test Methods

For specific information regarding susceptibility test interpretive criteria and associated test methods and quality control standards recognized by FDA for this drug, please see: https://www.fda.gov/STIC .

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.


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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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