Adverse Drug Reactions in an Intensive Care Unit of a Secondary Care Lithuanian Hospital: A Prospective Observational Study.

: Previous studies have shown that a major part of adverse drug reactions (ADRs) are preventable, and they contribute to increased morbidity, mortality, and costs. To our knowledge, no study investigating preventable ADRs has been carried out in Lithuania. Therefore, the aim of this study was to characterize ADRs in the intensive care unit (ICU) of a secondary care Lithuanian hospital as well as to identify drug classes and organ systems most commonly implicated in preventable and nonpreventable ADRs. : This observational prospective study was conducted in an 18-bed ICU of Kaunas Hospital of the Lithuanian University of Health Sciences from 1 September 2021 to 31 August 2023. All ADRs were assessed for causality, severity, and preventability. The Anatomical Therapeutic and Chemical (ATC) system was used to classify drug classes implicated in ADRs. The organ systems affected were analyzed using the Medical Dictionary for Regulatory Activities (MedDRA). : A total of 154 patients with a median age of 78.8 years (range, 18-97) were enrolled into this study. There were 255 ADRs identified; preventable ADRs accounted for 87.5%. Among the preventable ADRs, the top three therapeutic subgroups were antithrombotic agents (26.5%), anti-inflammatory and antirheumatic products (22.0%), and blood substitutes and perfusion solutions (20.2%). Meanwhile, among nonpreventable ADRs, antibacterials for systemic use (62.5%) and antithrombotic agents (46.9%) were the two most common therapeutic subgroups. The gastrointestinal as well as the skin and subcutaneous tissues organ systems were more likely to be affected by nonpreventable ADRs (56.3% vs. 17.5%, ˂ 0.05 and 12.5% vs. 0.4%, ˂ 0.05, respectively), while the renal and urinary organ systems were more likely to be affected by preventable ADRs (38.1% vs. 6.3%, ˂ 0.05). : Our study showed a very high incidence of preventable ADRs (87.5%). Drugs affecting blood and blood-forming organs were most frequently implicated in these ADRs. This area deserves special attention and strategies need to be implemented to reduce the incidence of preventable ADRs and their impact on the healthcare system. Moreover, it emphasizes the need for future studies at a national level as, to our knowledge, this is the first study addressing the issues of avoidable harm at the ICU of one Lithuanian hospital.