Potentially Inappropriate Medication Use among Nursing Home Residents: Medication Errors Associated with Pro re nata Medications and the Importance of Pill Burden

Background: The use of potentially inappropriate medications (PIM) has become more common among nursing home residents (NHR). This study focused on drugs initially prescribed as pro re nata (PRN) medications and pill burden in association with PIM among NHR. Methods: This observational cross-sectional study was conducted between March and April 2019 on 225 adult NHR aged ≥60 years. Results: The prevalence of PIM was 47.6% among NHR according to the Screening Tool of Older Persons' Prescriptions (STOPP) criteria version 2. The most frequent PIM was the use of any drug prescribed without evidence-based clinical indication; most medication errors were associated with PRN medications. The prevalence rates of PRN in non-PIM and PIM users were 12% and 62.4%, respectively. PRN medications that most commonly caused PIM were non-steroidal anti-inflammatory drugs and proton pump inhibitors. The cut-off value for both medications and pills to correctly identify participants with PIM was 5.5. Pill burden had a similar sensitivity to polypharmacy in identifying individuals with PIM.Conclusion: Medication errors associated with PRN medications were overlooked as factors that increased the risk of PIMs. The most common error related to PRN medications was the continued daily use despite symptom resolution.