Prevalence of hospitalisation caused by adverse drug reactions at an internal medicine ward of a single centre in Japan: a cross-sectional study

Objectives Few studies have investigated the prevalence of adverse drug reactions (ADRs) leading to hospitalisation in Japan. The aim of this study was to determine the prevalence of ADRs leading to hospitalisation and to evaluate the preventability of these ADRs in Japan. Design A single-centre cross-sectional study using electronic medical records. Setting Acute care hospital. Participants All 1545 consecutive hospital admissions to an internal medicine ward due to acute medical illnesses from April 2017 to May 2018. The median patient age was 79 years (IQR 66–87), and the proportion of women was 47.9%. Outcome measures The primary outcome was the proportion of hospitalisations caused by ADRs among all hospitalisations. All suspected cases of ADRs were independently evaluated by two reviewers, and disagreements were resolved by discussion. The causality assessment for ADRs was performed by using the WHO-Uppsala Monitoring Committee criteria. The contribution of ADRs to hospitalisation and their preventability were evaluated based on the Hallas criteria. Results Of the 1545 hospitalisations, 153 hospitalisations (9.9%, 95% CI 8.4% to 11.4%) were caused by 200 ADRs. Cardiovascular agents (n=46, 23.0%), antithrombic agents (n=33, 16.5%), psychotropic agents (n=29, 14.5%) and non-steroidal anti-inflammatory drugs (n=24, 12.0%) accounted for approximately two-thirds of all ADRs leading to hospitalisation. Of 153 hospitalisations caused by ADRs, 102 (66.7%) were judged to be preventable. Conclusions Similar to other countries, one in every ten hospitalisations is caused by ADRs according to data from an internal medicine ward of a Japanese hospital. Most of these hospitalisations are preventable. Some efforts to minimise hospitalisations caused by ADRs are needed.