The Prevalence of Drug-Drug Interaction and Inappropriate Drug Prescription Among the Elderly in Kashan

Background: Drug-drug Interaction (DDI) among the elderly is one of the major healthcare challenges worldwide. The present study assessed the rates of DDI and inappropriate drug prescription among the elderly in Kashan City, Iran.  Methods: This descriptive-analytical study was designed, conducted, and reported according to the guideline of Strengthening the Reporting of Observational Studies in Epidemiology (STROBE). A random sample of 368 elderly who lived in Kashan City, Iran, was selected through cluster sampling technique. Data collection tools were a demographic questionnaire and a drug checklist. The obtained data were analyzed by the Chi-squared test, logistic regression analysis, and Odds Ratio (OR) in SPSS.  Results: In total, 308 (88%) participants used at least one drug. The Mean±SD scores of daily consumed drugs and the number of inappropriate drugs taken daily by the study participants were 6.21±3.52 and 0.28±0.62, respectively. Most of the study participants were taking more than two drugs (n=267, 86.68%) and more than four drugs (n=200, 64.9%) per day. The OR of DDI among the study participants who were taking ≥2 drugs per day was 2.49 times greater than those who were taking one or two drugs (OR=2.49, 95% confidence interval=1.20-5.18). The most frequent DDIs were between non-steroidal anti-inflammatory drugs and beta-blocker agents (n=84, 18.22%) and between non-steroidal anti-inflammatory drugs and nitrates (n=46, 9.9%).  Conclusion: The rate of inappropriate drug use among the elderly living in Kashan, Iran, is low, however, polypharmacy and DDIs are highly prevalent among them. To reduce the rates of DDI and polypharmacy, educational programs for different healthcare providers are required to improve their knowledge. Moreover, further studies are needed to assess the effects of polypharmacy and DDI preventive measures, like drug history cards.