Hospital admissions/visits associated with drug–drug interactions: a systematic review and meta‐analysis

To estimate prevalences of hospital admissions/visits associated with actual drug-drug interactions (DDIs) and examine the effect of study design (prospective vs. retrospective), population (all ages or adults), and method of detecting DDIs on reported prevalences.PubMed, International Pharmaceutical Abstracts, Excerpta Medica Database, Cumulative Index to Nursing and Allied Health Literature plus, and the Cochrane Database of Systematic Reviews up to October 2013 were searched for observational studies examining actual DDIs, in any language. The outcomes in this study were DDI prevalence rates in total populations, DDI prevalence rates in total adverse drug reaction patients, and frequency (%) of each pair of DDIs.Thirteen studies met our inclusion criteria. The median DDI prevalence rate for hospital admissions was 1.1% (367 DDI cases/47 976 patients, interquartile range [IQR] 0.4-2.4%). The median DDI prevalence rate for hospital visits was 0.1% (20 DDI cases/23 607 patients, IQR 0.0-0.3%). In adverse drug reaction patients, the median DDI prevalence rate for hospital admissions (308 DDI cases/1683 patients) and hospital visits (8 DDI cases/90 patients) were 22.2% (IQR 16.6-36.0%) and 8.9%, respectively. Medical record, interview, drug interaction screening program, adverse reaction report, and electronic medical record were identified as methods used for detecting DDIs. Non-steroidal anti-inflammatory drugs were most commonly involved in hospital admission associated DDIs, whereas warfarin was frequently involved in DDIs detected at hospital visits as outpatients/emergencies.Drug-drug interactions are a significant cause of hospital admissions and hospital visits. Improved DDI information gathering could help to reduce such adverse effects from DDIs, especially for patients using non-steroidal anti-inflammatory drugs and warfarin.