Socioeconomic inequalities in self-medication with antibiotics in southern Tehran: findings from a population-based survey

In countries where antibiotics are often sold without a prescription, such as Iran, widespread self-medication with antibiotics (SMA) occurs. This behavior reflects broader socioeconomic inequalities that influence health practices. However, empirical evidence from Iran remains insufficient, and the study was conducted to investigate socioeconomic inequalities in SMA among the Iranian population in southern Tehran. This secondary analysis used data from the 2023 Integrated and Repeated Public Health Surveillance System (IRPHS), a cross-sectional telephone survey of 1,311 adults in three regions of southern Tehran. Participants with available data on socioeconomic status (SES) and SMA were included in the descriptive analyses ( n = 1,262). Missing covariate data were handled pairwise deletion for descriptive analyses, while complete-case analysis was used for regression, inequality, and decomposition analyses, yielding 1,123 participants. A structured composite index was developed using data on SES and the frequency of SMA, which was examined using the concentration index (CI) and Wagstaff’s decomposition method. After addressing the missing data, the analysis indicates that among the 1,262 participants, with a mean ± standard deviation (SD) age of 40.1 ± 13.2 years, and a gender distribution of 500 males (39.56%) vs. 762 females (60.44%). The prevalence of health-related factors such as access to basic insurance, mental mood, and education improved with higher SES. Participants with higher SES demonstrated a significantly higher prevalence of desirable health indicators, specifically basic health insurance coverage and high mental mood, compared to those with lower SES. The distribution of educational attainment varied significantly across SES groups, with a lower proportion of illiteracy/primary education but also a lower proportion of academic education in the high SES group. The CI was positive and statistically significant (CI: 0.205; p < 0.001), indicating a pro-rich pattern of inequality. Decomposition analysis revealed that 54.76% of the total inequality was explained, primarily by basic health insurance (43.37%) and education level (up to 10.23%), as the main positive contributors. In contrast, understanding of physicians’ explanations showed the largest negative contribution (− 75.11%). SMA showed a socially patterned, predominantly pro-rich distribution in southern Tehran. These findings support context-specific antimicrobial stewardship strategies addressing social and behavioral determinants, strengthening prescription regulations and provider–patient communication. Future studies should explore the mechanisms underlying these patterns and evaluate interventions to reduce inappropriate antibiotic self-medication.