Assessment of Inappropriate Omeprazole Prescribing, Associated Factors and Financial Impact in the Outpatient Department of a General Hospital in Thailand

Background: Proton pump inhibitors (PPIs) are widely used for the treatment of gastrointestinal (GI) disorders. Omeprazole is one of the most commonly prescribed PPIs in Thailand. However, it is frequently overprescribed in hospital settings, increasing the risk of adverse effects. Moreover, such overuse imposes unnecessary healthcare costs. Objectives: To determine the prevalence of potentially inappropriate omeprazole prescribing and its associated factors, and to assess the financial impact of its overuse. Methods: This retrospective cross-sectional study was conducted in a general hospital in Thailand. Outpatients who received omeprazole between 1 January 2025 and 30 June 2025 were included. Descriptive statistics were used to summarize the data. The Chi-square test and Fisher’s exact test were used to compare categorical variables, as appropriate. Factors associated with inappropriate omeprazole prescribing were evaluated using logistic regression analysis. Results: A total of 229 patients receiving 347 omeprazole prescriptions were included. The mean age was 61.35 ± 17.17 years, and 59.4% were female. Inappropriate omeprazole prescribing was identified in 58.2% of prescriptions, primarily due to lack of appropriate indications (75.2%), followed by inappropriate duration. Antiplatelet use (OR 0.21, 95% CI 0.11–0.38, p < 0.001) and dual antiplatelet therapy (OR 0.05, 95% CI 0.01–0.37, p = 0.004) were significantly associated with a lower likelihood of inappropriate prescribing. Conclusion: Inappropriate omeprazole prescribing was common and largely driven by the absence of a clear indication, which was the main contributor to excess costs. Targeted interventions focusing on appropriate initiation, GI risk assessment, and regular reassessment may improve prescribing quality and reduce unnecessary healthcare expenditure.