Incident adverse drug reactions in geriatric inpatients: a multicentred observational study

Background: Adverse drug reactions (ADRs) are common in older adults and frequently have serious clinical and economic consequences. This study was conducted as a feasibility study for a randomized control trial (RCT) that will investigate the efficacy of a software engine to optimize medications and reduce incident (in-hospital) ADRs. This study’s objectives were to (i) establish current incident ADR rates across the six sites participating in the forthcoming RCT and (ii) assess whether incident ADRs are predictable. Methods: This was a multicentre, prospective observational study involving six European hospitals. Adults aged ⩾ 65 years, hospitalized with an acute illness and on pharmacological treatment for three or more conditions were eligible for inclusion. Adverse events (AEs) were captured using a trigger list of 12 common ADRs. An AE was deemed an ADR when its association with an administered drug was adjudicated as being probable/certain, according to the World Health Organization Uppsala Monitoring Centre causality assessment. The proportion of patients experiencing at least one, probable/certain, incident ADR within 14 days of enrolment/discharge was recorded. Results: A total of 644 patients were recruited, evenly split by sex and overwhelmingly of White ethnicity. Over 80% of admissions were medical. The median number of chronic conditions was five (interquartile range 4–6), with eight or more conditions present in approximately 10%. The mean number of prescribed medications was 9.9 (standard deviation 3.8), which correlated strongly with the number of conditions (r = 0.54, p < 0.0001). A total of 732 AEs were recorded in 382 patients, of which 363 were incident. The majority of events were classified as probably or possibly drug related, with heterogeneity across sites (χ² = 88.567, df = 20, p value < 0.001). Out of 644 patients, 139 (21.6%; 95% confidence interval 18.5–25.0%) experienced an ADR. Serum electrolyte abnormalities were the most common ADR. The ADRROP (ADR Risk in Older People) and GerontoNet ADR risk scales correctly predicted ADR occurrence in 61% and 60% of patients, respectively. Conclusion: This feasibility study established the rates of incident ADRs across the six study sites. The ADR predictive power of ADRROP and GerontoNet ADR risk scales were limited in this population.