Proton pump inhibitors (PPIs) decrease the rate of rebleeding following endoscopic hemostatic therapy in patients with bleeding peptic ulcers. This study compares the efficacy of oral omeprazole vs intravenous omeprazole in decrease of rebleeding of peptic ulcer patients.The present study was authorized by the local research ethics committee of Jiangjin District Central Hospital (2020120987) and informed consent was obtained from all patients. All adult patients who were admitted to medical emergency rooms of Jiangjin District Central Hospital due to upper gastrointestinal bleeding (as evidenced by hematemesis, melena or hematochezia) were considered for inclusion in the study. Endoscopy was performed within 24 hours after admission. Patients older than 18 years with successful endoscopic therapy of high risk ulcers [defined as active bleeding (Forrest IA, IB), non-bleeding visible vessel (NBVV, Forrest IIA) or adherent clots (Forrest IIB)] were enrolled. Patients with low risk ulcers (clean base, ulcers with a simple washable clot), suspicious malignant ulcer, bleeding tendency, uremia, liver cirrhosis, Mallory Weiss tear or already on PPI as an outpatient were excluded from study. All were managed endoscopically by injecting 5-30 ml of epinephrine (diluted 1:10000) around the ulcer crater. Cavitations or flattening of bleeding vessel and disappearance of NBVV was considered as established homeostasis. A biopsy was taken from antrum for evaluating Helicobacter pylori infection. Patient with unsuccessful endoscopic therapy were not enrolled and were referred to general surgeon. Information on demography, history of previous upper gastrointestinal bleeding, NSAID or ASA ingestion, ulcer location, bleeding stigmata and blood transfusion volume at entry were recorded in all patients. In the oral omeprazole group, the patients received 40 mg omeprazole orally twice daily for 72 hours. In intravenous omeprazole group, they received omeprazole 80 mg bolus and then 8 mg/hour infusion for 48-72 hours. Then, all patients received omeprazole 20 mg orally for 30 days. On the day of discharge Helicobacter pylori infected patients received standard regimens.Figure 1 showed the primary and secondary end points.Intravenous administration of PPIs has limitations. They are expensive, require a dedicated intravenous line, need nursing supervision and hospital admission. So, it would be reasonable to prescribe oral PPIs to patients with high risk bleeding ulcers provided that it is as effective as its intravenous counterpart. Oral PPIs have a high bioavailability. Its effect initiates one hour after ingestion and the maximal plasma concentration is achieved after 2-3 hours. However, there are few studies comparing oral and intravenous PPI in decreasing risk of rebleeding in peptic ulcer patients. More high quality randomized controlled trials are still necessary.researchregistry 6588.