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Clinical Pharmacology

In the esomeprazole magnesium/amoxicillin/clarithromycin clinical trials, 83% (176/212) of the patients in the esomeprazole magnesium/amoxicillin/clarithromycin treatment group who had pretreatment amoxicillin susceptible MICs ( ≤ 0.25 mcg/mL) were eradicated of H. pylori, and 17% (36/212) were not eradicated of H. pylori. Of the 36 patients who were not eradicated of H. pylori on triple therapy, 16 had no post-treatment susceptibility test results and 20 had post-treatment H. pylori isolates with amoxicillin susceptible MICs. Fifteen of the patients who were not eradicated of H. pylori on triple therapy also had post-treatment H. pylori isolates with clarithromycin resistant MICs. There were no patients with H. pylori isolates who developed treatment emergent resistance to amoxicillin.

Susceptibility Test for Helicobacter pylori: The reference methodology for susceptibility testing of H. pylori is agar dilution MICs. One to three microliters of an inoculum equivalent to a No.2 McFarland standard (1 x 107 - 1 x 108 CFU/mL for H. pylori) are inoculated directly onto freshly prepared antimicrobial containing Mueller-Hinton agar plates with 5% aged defibrinated sheep blood ( ≥ 2 weeks old). The agar dilution plates are incubated at 35°C in a microaerobic environment produced by a gas generating system suitable for Campylobacter. After 3 days of incubation, the MICs are recorded as the lowest concentration of antimicrobial agent required to inhibit growth of the organism. The clarithromycin and amoxicillin MIC values should be interpreted according to the following criteria:

Table 8

Clarithromycin MIC (mcg/mL)a Interpretation
≤ 0.25 Susceptible(S)
0.5 Intermediate(I)
≥ 1.0 Resistant(R)
Amoxicillin MIC (mcg/mL)a,b Interpretation
≤ 0.25 Susceptible(S)
a These are breakpoints for the agar dilution methodology and they should not be used to interpret results obtained using alternative methods.
b There were not enough organisms with MICs > 0.25 mcg/mL to determine a resistance breakpoint.

Standardized susceptibility test procedures require the use of laboratory control microorganisms to control the technical aspects of the laboratory procedures. Standard clarithromycin and amoxicillin powders should provide the following MIC values:

Table 9

Microorganism Antimicrobial Agent MIC (mcg/mL)a
H. pylori ATCC 43504 Clarithromycin 0.016 – 0.12 (mcg/mL)
H. pylori ATCC 43504 Amoxicillin 0.016 – 0.12 (mcg/mL)
a These are quality control ranges for the agar dilution methodology and they should not be used to control test results obtained using alternative methods.

Animal Toxicology and/or Pharmacology

Reproductive Toxicology Studies

Reproductive studies have been performed in rats at oral doses up to 280 mg/kg/day (about 57 times the human dose on a body surface area basis) and in rabbits at oral doses up to 86 mg/kg/day (about 35 times the human dose on a body surface area basis) and have revealed no evidence of impaired fertility or harm to the fetus due to esomeprazole.

Reproductive studies conducted with omeprazole in rats at oral doses up to 138 mg/kg/day (about 56 times the human dose on a body surface area basis) and in rabbits at doses up to 69 mg/kg/day (about 56 times the human dose on a body surface area basis) did not disclose any evidence for a teratogenic potential of omeprazole. In rabbits, omepraozle in a dose range of 6.9 to 69.1 mg/kg/day (about 5.5 to 56 times the human dose on a body surface area basis) produced dose-related increases in embryo-lethality, fetal resorptions, and pregnancy disruptions. In rats, dose-related embryo/fetal toxicity and postnatal developmental toxicity were observed in offspring resulting from parents treated with omeprazole at 13.8 to 138.0 mg/kg/day (about 5.6 to 56 times the human doses on a body surface area basis).

Clinical Studies

Healing of Erosive Esophagitis
Brand Name: Nexium
Generic Name: Esomeprazole Magnesium

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