Prevalence, Determinants, and Objective Risk of Unintentional Therapeutic Duplication Among Adults in Saudi Arabia

Abstract: Background: Unintentional therapeutic duplication represents an underrecognized yet preventable contributor to medication-related harm, particularly in settings characterized by widespread over-the-counter (OTC) medicine use and self-medication practices. Objective: To estimate the prevalence of unintentional therapeutic duplication among adults in Saudi Arabia and identify sociodemographic and behavioral predictors associated with increased therapeutic duplication risk. Methods: A national cross-sectional study was conducted between February 10 and April 28, 2025, using a structured, self-administered online questionnaire distributed via social media platforms. The survey assessed sociodemographic characteristics, medication-use behaviors, active-ingredient literacy, and duplication risk using both self-reported measures and scenario-based assessments. Multivariable logistic regression was performed to identify independent predictors of elevated therapeutic duplication risk. Results: A total of 700 participants were included (mean age 34.2 ± 10.5 years; 58% female). The prevalence of self-reported therapeutic duplication within the preceding 90 days was 43.0%. Paracetamol-containing products were the most commonly implicated (32.0%), followed by nonsteroidal anti-inflammatory drugs (24.0%) and antihistamines (15.0%). The mean ingredient-literacy score was 5.1 ± 2.3 (out of 10), with only 48% correctly identifying duplication scenarios. In adjusted analysis, poor ingredient literacy (AOR 3.12, 95% CI 2.29–4.25), frequent OTC use (AOR 2.41, 95% CI 1.78–3.26), and lower educational attainment (AOR 1.89, 95% CI 1.32–2.71) were independently associated with increased duplication risk ( p < 0.001). Conclusion: Unintentional therapeutic duplication is common among adults in Saudi Arabia and is strongly associated with limited active-ingredient literacy. Targeted interventions focusing on patient education, improved labeling, and pharmacist-led counseling are warranted to mitigate preventable medication harm. Key Words: Therapeutics; Duplication; Saudi Arabia; public; ingredient.