Potential clinically significant drug-drug interactions in prescribed pharmacotherapy in an outpatient setting.

The aim of this study was to determine the most common potential clinically significant drug-drug unteractions (DDIs) in prescribed pharmacotherapy in an outpatient setting in Croatia. Twelve community pharmacies were randomly selected in this research. Retrospective pharmacotherapy record data analysis was conducted on consecutive eligible patients. Potential DDIs were detected using Lexicomp software that categorizes DDIs according to clinical significance. Categories C (monitor drug therapy), D (consider therapy modification) and X (avoid combination) are of clinical concern. In total, 1211 patients were enrolled in this study. The results showed that 84% of patients had at least one clinically significant interaction. The average number of interactions per patient was 4. Overall, 4798 potentially clinically significant DDIs were identified; 3945 (82.2%) required therapy monitoring, while other interactions (D and X category) required specific therapy modification. According to the level of clinical significance the most common clinical consequences of identified potential drug interactions were increased risk of hypotension, impaired renal function, central nervous system depression, gastrointestinal toxicity and QTc prolongation. Research indicates the high exposure to potential clinically significant DDIs in the prescribed pharmacotherapy in an outpatient setting and imposes the need for standardised models of pharmacist interventions.