OBJECTIVES: To investigate the cost-effectiveness of high dose IV omeprazole as an adjuvant therapy to endoscopic hemostasis for prevention of early ulcer rebleeding from a hospital perspective. A randomized, placebo-controlled clinical trial was conducted previously in a local hospital to study the effects of high dose IV omeprazole infusion on patient outcomes after endoscopic ulcer hemostasis. Although the interim data suggested that IV omeprazole significantly decreased the rate of early rebleeding that occurred 72 hours after therapy, the cost implication of this therapy has not been examined. METHODS: The data of 157 patients who completed the above study was analyzed. The percentages of patients who experienced early rebleeding were obtained from medical records. The health care resources consumed by each patient during the first 72 hours post endoscopic hemostasis were also retrieved from their records and studied. RESULTS: Four of 80 (5%) patients in the omeprazole group and 17 of 77 (22%) patients from the placebo group had rebleeding within 72 hrs after endoscopy and required further treatment. The treatment cost within 72 hours post endoscopy of the IV omeprazole group was lower than that of the placebo group (HK$1312 per patient vs. $3223 per patient, 1 US = 7.8 HK). The cost-effectiveness ratios for the omeprazole group and placebo group were $9,946 and $12,821, respectively, per early rebleeding episode prevented. CONCLUSIONS: High dose omeprazole is more cost-effective in preventing early ulcer rebleeding than placebo after endoscopic hemostasis.