The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Peter Katelaris - One of the best experts on this subject based on the ideXlab platform.
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the effect of dosing with Omeprazole on the accuracy of the 13c urea breath test in helicobacter pylori infected subjects
Alimentary Pharmacology & Therapeutics, 1999Co-Authors: S J Connor, Francis Seow, Meng C Ngu, Peter KatelarisAbstract:Background : The 13C-urea breath test (13C-UBT) is an accurate means of Helicobacter pylori diagnosis. However, proton pump inhibitors may suppress H. pylori and cause false negative results. Aim : To study the kinetics of H. pylori suppression by Omeprazole during and after short-term use. Methods : Volunteers underwent a baseline 13C-UBT (13C-urea 100 mg). H. pylori-positive subjects took Omeprazole 20 mg daily for 14 days. Those who remained 13C-UBT positive (δ13CO2 ≥ 5) continued Omeprazole for a further 14 days. 13C-UBTs were performed weekly on Omeprazole and then every second day after it was stopped. False negatives occurred when δ13CO2 fell to < 5. Results : In 25 H. pylori-positive subjects (mean age 43.9 ± 2.4 years; 21 females, 4 males) the mean baseline δ13CO2 was 28.1 ± 3.4. False negative breath tests occurred in three subjects after 7 days of Omeprazole and in a further four subjects after 14 days. A further six subjects developed negative tests between Days 14 and 28. Following cessation of Omeprazole, the 13C-UBT became positive again in 12/13 subjects within 4 days and in all within 6 days, with a mean recovery to 99.9 ± 18.6% of baseline δ13CO2. Conclusions : False negative 13C-UBTs are common during treatment with Omeprazole and occur after as little as 7 days. Return to positive test results is rapid after cessation of Omeprazole. These findings are relevant to the timing of testing in clinical practice.
James M Scheiman - One of the best experts on this subject based on the ideXlab platform.
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prolonged effect of Omeprazole on the 14c urea breath test
The American Journal of Gastroenterology, 1996Co-Authors: William D Chey, Mark Spybrook, Steve Carpenter, Timothy T Nostrant, Grace H Elta, James M ScheimanAbstract:Objectives: We investigated Omeprazole's effect on '''C-urea breath testing. We also determined the duration of Omeprazole's effect on the breath test. Finally, we studied whether effects on breath testing were dose dependent. Methods: Fifty-seven employees and outpatients were screened for Helicobacter infection. Those positive for serology, CLO, or histology were asked to undergo baseline breath testing. Those with a positive breath test took Omeprazole 20 mg/day for 14 days followed by repeat breath testing 1, 3, and 5 days after therapy. Subjects with persistently positive breath tests despite Omeprazole 20 mg/day were asked to take Omeprazole 20 mg b.Ld. for 14 days. Repeat breath tests were performed as above. Results: Thirteen of 57 had HP infection. Ten of 13 underwent a baseline breath test. Eight of 10 with baseline breath tests experienced a significant decrease in expired ""COj after Omeprazole 20 mg/day. Five of 13 with active HP infection developed a negative breath test after Omeprazole. All subjects had a positive breath test within 5 days of stopping Omeprazole 20 mg/day. Five of eight with persistently positive breath tests despite Omeprazole 20 mg/day took Omeprazole 40 mg/day. Four of five developed a significant decrease in ^''COz excretion after Omeprazole. All subjects had a positive breath test within 5 days of stopping Omeprazole 40 mg/day. Conclusions: Recent treatment with Omeprazole 20 mg/day led to false-negative breath tests in 38.5%. This effect appeared to be dose dependent and lasted up to 5 days after cessation of Omeprazole.
Donald O. Castell - One of the best experts on this subject based on the ideXlab platform.
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Control of intragastric pH with Omeprazole 20 mg, Omeprazole 40 mg and lansoprazole 30 mg
Alimentary pharmacology & therapeutics, 2001Co-Authors: Philip O Katz, S. Xue, Donald O. CastellAbstract:Background: Single daily doses of proton pump inhibitors, Omeprazole and lansoprazole provide effective acid suppression and equal healing and symptom relief in patients with GERD. Despite this, controversy exists as to the efficacy of available proton pump inhibitors in the control of gastric acidity. Aim: To assess the efficacy of Omeprazole 20 mg vs. lansoprazole 30 mg and Omeprazole 40 mg vs. lansoprazole 30 mg in intragastric pH control. Methods: Study I: 12 Helicobacter pylori-negative volunteers (mean age 33 years) were treated with Omeprazole 20 mg and lansoprazole 30 mg in random order before breakfast for 7 days. Study II: 24 subjects (mean age 36 years) were similarly treated with Omeprazole 40 mg and lansoprazole 30 mg for 7 days after a baseline pH study. One week washout was allowed between studies. Subjects had the same meal on each study day. On day seven, a 24-h intragastric pH study was performed. The percentage time for which gastric pH > 4 was analysed (Gastrosoft, Synectics Medical Inc.) and expressed as mean ± s.d. Results: (1) Omeprazole 20 mg and lansoprazole 30 mg showed no significant difference in the percentage time for which gastric pH > 4 in the daytime and night-time periods. (2) The percentage time for which pH > 4 with Omeprazole 40 mg was significantly greater than lansoprazole 30 mg in both daytime (61 ± 19% vs. 48 ± 14%, P 4 in the daytime (69 ± 18% vs. 51 ± 15%, P=0.015) than Omeprazole 20 mg. Conclusion: These pH data support the therapeutic equivalency of FDA approved doses of Omeprazole and lansoprazole.
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Persistent acid secretion during Omeprazole therapy: a study of gastric acid profiles in patients demonstrating failure of Omeprazole therapy.
The American journal of gastroenterology, 1996Co-Authors: Louis P. Leite, Brian T. Johnston, R J Just, Donald O. CastellAbstract:Objective : To identify patients with gastroesophageal reflux disease (GERD) who, despite Omeprazole 20 mg b.i.d., demonstrate continued abnormal gastric acid secretion. Methods : Eighty-eight patients with GERD completed ambulatory gastric and esophageal pH monitoring for persistent symptoms on Omeprazole 20 mg b.i.d.. Seventeen (19%) demonstrated abnormal gastric acid secretion (percentage time gastric pH 50%). The 17 Omeprazole failures (OF) were compared with : 1) 19 randomly selected patients with GERD (also studied on Omeprazole 20 mg b.i.d. and 2) 19 normal volunteers studied on both placebo and Omeprazole 20 mg b.i.d.. Total time intragastric pH < 4, 24-hr gastric pH frequency distribution, and 15-min median pH values for the 6-h period after the evening Omeprazole dose were compared. Results : Both the 24-hr frequency distribution for gastric pH and the 15-min median gastric pH profile for patients with GERD and volunteers on Omeprazole 20 mg b.i.d. were almost identical. By contrast, gastric pH studies from the OF group receiving Omeprazole 20 mg b.i.d. most closely resembled those of the normal subjects receiving placebo, with respect to these variables. Gastric pH monitoring in seven of the 17 OF patients while on Omeprazole 80 mg/day demonstrated a significant decrease in the median percentage time gastric pH remained below 4 (32.8% on 80 mg/day vs 74.3% on 40 mg/day ; p < 0.02). Conclusion : There are individuals whose intragastric acidity persists despite conventional doses of Omeprazole. Although the underlying mechanism remains unclear, the majority (six of seven) (87%) demonstrated improved gastric acid control when placed on high dose Omeprazole, indicating that this is often a dose-dependent phenomenon.
Nina Isoherranen - One of the best experts on this subject based on the ideXlab platform.
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inhibition of cyp2c19 and cyp3a4 by Omeprazole metabolites and their contribution to drug drug interactions
Drug Metabolism and Disposition, 2013Co-Authors: Yoshiyuki Shirasaka, Jennifer E Sager, Justin D Lutz, Connie L Davis, Nina IsoherranenAbstract:The aim of this study was to evaluate the contribution of metabolites to drug-drug interactions (DDI) using the inhibition of CYP2C19 and CYP3A4 by Omeprazole and its metabolites as a model. Of the metabolites identified in vivo, 5-hydroxyOmeprazole, 5′-O-desmethylOmeprazole, Omeprazole sulfone, and carboxyOmeprazole had a metabolite to parent area under the plasma concentration–time curve (AUCm/AUCp) ratio ≥ 0.25 when either total or unbound concentrations were measured after a single 20-mg dose of Omeprazole in a cocktail. All of the metabolites inhibited CYP2C19 and CYP3A4 reversibly. In addition Omeprazole, Omeprazole sulfone, and 5′-O-desmethylOmeprazole were time dependent inhibitors (TDI) of CYP2C19, whereas Omeprazole and 5′-O-desmethylOmeprazole were found to be TDIs of CYP3A4. The in vitro inhibition constants and in vivo plasma concentrations were used to evaluate whether characterization of the metabolites affected DDI risk assessment. Identifying Omeprazole as a TDI of both CYP2C19 and CYP3A4 was the most important factor in DDI risk assessment. Consideration of reversible inhibition by Omeprazole and its metabolites would not identify DDI risk with CYP3A4, and with CYP2C19, reversible inhibition values would only identify DDI risk if the metabolites were included in the assessment. On the basis of inactivation data, CYP2C19 and CYP3A4 inhibition by Omeprazole would be sufficient to identify risk, but metabolites were predicted to contribute 30–63% to the in vivo hepatic interactions. Therefore, consideration of metabolites may be important in quantitative predictions of in vivo DDIs. The results of this study show that, although metabolites contribute to in vivo DDIs, their relative abundance in circulation or logP values do not predict their contribution to in vivo DDI risk.
P. Milla - One of the best experts on this subject based on the ideXlab platform.
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Electrolyte disturbance with Omeprazole therapy.
European journal of pediatrics, 1994Co-Authors: C. Melville, A. Shah, D. Matthew, P. MillaAbstract:Omeprazole is an antagonist to the H+K+ ATPase of the gastric parietal cell. We report a case of severe electrolyte disturbance in a 5-year-old child treated with Omeprazole associated with excessive urinary sodium loss, that responded completely to Omeprazole with-drawal.
