Antimicrobial use and drug–drug interactions among nursing home residents in Singapore: a multicentre prevalence study

Background With the Ministry of Health’s projected increase in nursing home beds and optimization of antimicrobial use in health care settings, it is therefore timely to consider baseline prevalence and patterns of antimicrobial use at nursing homes in Singapore as well as to evaluate the prevalence of potential clinically significant drug–drug interactions involving antimicrobials. Objective The primary objective was to determine the prevalence and patterns of antimicrobial use at nursing homes in Singapore. The secondary objective was to evaluate the prevalence of potential clinically significant drug–drug interactions involving antimicrobials. Setting Four nursing homes in Singapore. Method A retrospective cross-sectional study was conducted among nursing home residents. The antimicrobial prevalence, defined daily doses, days of therapy, and potential drug–drug interactions were determined using data from archived resident medication prescribing and administration records. Main outcome measure Prevalence and patterns of antimicrobial use, drug–drug interactions involving antimicrobials. Results Among 707 residents (mean age: 80.7 ± 8.8 years, female: 57.1%), 10% used antimicrobials during the study month, with a 1-day point prevalence of 3%. The utilization rates of antimicrobials were 28.9 defined daily doses/1000 resident-days and 24.8 days of therapy/1000 resident-days. Potential drug–drug interactions involving antimicrobials were identified among 32 of the 70 (46%) residents who were prescribed antimicrobials. Of these, 26 (81%) residents had 43 potential clinically significant drug–drug interactions. Conclusions The prevalence and utilization rates of antimicrobial use in Singapore nursing homes appear to be low. Yet, potential clinically significant drug–drug interactions are prevalent.