Pharmacological Study That Measures Omeprazole Effect on Aspirins Absorption in Healthy Volunteers


Aspirin is a weak acid that crosses the gastric and intestinal mucosa by passive diffusion while in its lipophilic nature.Omeprazole, a proton pump inhibitor, inhibits gastric acid secretion. We assumed that omeprazole inhibits aspirin absorption, thus reducing its action on platelets. healthy volunteers, with no known peptic disease or bleeding disorders will be enrolled. All volunteers will receive 7 days of Aspirin (100mg) alone, followed by 14 days of Aspirin and Omeprazole 20mg twice daily for 3 days and then 20mg once daily. Blood levels of Aspirin will be determined by High performance liquid chromatography (HPLC), 0, 1, 2, 4, 6, 10, 24 hours after the administration of Aspirin alone on day 7 and Aspirin plus Omeprazole on day 21. Platelet function tests will be determined by platelet-rich plasma aggregometry in response to Arachidonic acid (500mg/ml), Ristocetin (1.5mg/ml) and Adenosine 5'-diphosphate (20mM) on day 0 as baseline and on day 7 and 21 of the study.

Full Title of Study: “The Effect of Proton Pump Inhibitor (Omeprazole) on Acetosalisylic Acid Absorption.”

Study Type

  • Study Type: Interventional
  • Study Design
    • Allocation: N/A
    • Intervention Model: Single Group Assignment
    • Masking: None (Open Label)
  • Study Primary Completion Date: June 2007


  • Drug: aspirin and omeprazole
    • aspirin 100 mg, once daily aspirin 100 mg and omeprazole 20 mg both once daily.

Clinical Trial Outcome Measures

Primary Measures

  • Aspirin Level in Blood (Area Under the Curve)
    • Time Frame: on day 7,on day 21
    • Aspirins pharmacokinetics: aspirin blood level determined by use of high performance liquid chromatography (HPLC) at baseline, 1, 2,4,6,10 and 24 hours after administration of aspirin on day 7 and on day 21. The area unther the time vs. concentration curve of the reccurent measurments(AUC) reflects bioavailability of aspirin.

Secondary Measures

  • Platelet Function Tests
    • Time Frame: on day 0 as a baseline and on day 7 and 21 of the study.
    • Platelet function tests were determined by optical whole blood aggregometry in response to arachidonic acid and adenosine diphosphate. the results reflects the percent of active platelets.

Participating in This Clinical Trial

Inclusion Criteria

-healthy volunteers Exclusion Criteria:

  • pretreatment with aspirin – pretreatment with non steroidal anti inflamatory drugs – pretreatment with antacids – history of peptic ulcer disease – coagulation or aggregation disorder.

Gender Eligibility: All

Minimum Age: 18 Years

Maximum Age: 60 Years

Are Healthy Volunteers Accepted: No

Investigator Details

  • Lead Sponsor
    • Assaf-Harofeh Medical Center
  • Provider of Information About this Clinical Study
    • dr. keren doenyas barak, internal medicine A asaf-harofeh medical center
  • Overall Official(s)
    • ahuva golik, prop., Study Director, asaf-harofemedical center

Clinical trials entries are delivered from the US National Institutes of Health and are not reviewed separately by this site. Please see the identifier information above for retrieving further details from the government database.

At, we keep tabs on over 200,000 clinical trials in the US and abroad, using medical data supplied directly by the US National Institutes of Health. Please see the About and Contact page for details.