Point–Prevalence of Antimicrobial–Related Potential Drug–Drug Interactions in Hospitalized Older Adults: A Multicenter Study Using Lexicomp

Background/Objectives: Potential drug–drug interaction (pDDI) refers to the co–administration of two or more drugs that interact with each other and may have therapeutic effects. Increasing rates of polypharmacy with age increase the risk of pDDIs in geriatric patients. This multicenter study aims to provide real–world data on the incidence of pDDI associated with antimicrobial therapy in hospitalized older adults. Methods: The study screened all hospitalized patients, including those aged 65 years and older. Using the Lexicomp® Drug Interaction Online Database, researchers screened for pDDIs among all medications taken by patients. Results: 663 (24.0%) aged 65 and over were included in the study. Polypharmacy was present in 64.9%, and hyperpolypharmacy was present in 10.0% of the cases. 480 (72.4%) of the cases used antimicrobial therapy. The mean total number of drugs and antimicrobials used per case was 5.86 and 1.02, respectively. A total of 372 antimicrobial–related pDDIs were detected, and at least one antimicrobial–related pDDI was identified in 202 (42%) patients receiving antimicrobials. Ciprofloxacin (73.3%), clarithromycin (58.3%), and colistin (26.3%) had the highest numbers of D–type pDDIs. The antimicrobials with the highest incidence of X–type pDDIs were metronidazole (23.6%) and clarithromycin (8.3%), respectively. The logistic analysis found a significant association between antimicrobial–related pDDIs and an increase in the number of drugs, length of hospital stays, and ID departments. Conclusions: PDDI rates associated with antimicrobials, like the high pDDI rates associated with all drugs, support the literature. Therefore, strategies should be developed to reduce the risk of pDDI when prescribing antimicrobials to geriatric patients.