Effect of Omeprazole on Gastric Mucosa and Serum
Levels of Amoxicillin in Patients with Non-Ulcer Dys-
pepsia
SUPEECHA WITTAYALERTPANYA,M.Sc.*, NATNIPA WANNACHAI, M.Sc.*,
PHENSRI THONGNOPNUA, Ph.D.**,
VAROCHA MAHACHAI, M.D., M.Sc., F.R.C.P.***
Affiliation : * Department of Pharmacology,
**
Department of Pharmaceutical Chemistry, Faculty of Pharmaceutical Science.
***
Department of Internal Medicine, Faculty of Medicine, Chulalongkorn University. Bangkok I 0330. Thailand.
AbstractThe aim of this study was to determine the interaction between omeprazole and
amoxicillin, being common agents used in the eradication regimen for H. pylori infection.
Amoxicillin concentrations in gastric mucosa and serum were quantitatively analysed in 12
patients with non-ulcer dyspepsia following the administration of one week duration of
placebo as group I and omeprazole as group II. The study was a blind, cross-over design with a
one week wash out period between the two treatment groups. Six antral gastric mucosa were
biopsied 90 minutes after oral administration of amoxicillin. Blood samples were collected
before and after administration at intervals up to 6 hours. All samples were analysed for
amoxicillin concentration using the HPLC technique. Highly intersubject variations of amoxicillin
concentrations were observed. The concentration of amoxicillin in gastric mucosa ranged from
0.00-1.74 and 0.00-1.25 flg/mg for group I and group II, respectively, with the mean concentra-
tion of 0.25±0.48 f.Jg/mg for group I and 0.28±0.40 f.Jg/mg for group II. The difference was
not statistically significant (p=0.89). Pharmacokinetic parameters of amoxicillin in serum
following regimen I and regimen II were not significantly different (p>0.05). The mean Cmax
values were 14.62±5.39 and 12.65±4.76 f.Jg/ml, the Tmax were 2.3±1.0 and 2.0±0.9 hour and the
AUC0_6 were 40.79±13.26 and 38.75±15.04 flg/ml.h in the group I and group II, respectively.
From these results, we concluded that omeprazole has no effect on gastric mucosa level nor
serum levels of amoxicillin. The therapeutic efficacy of using these two agents in the eradication
regimen of H. pylori may be related to other factors rather than pharmacokinetic interac-
tion.
Keywords : Gastric Mucosa, Amoxicillin, Omeprazole
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