Potential Drug-Drug Interactions among Three or More Drugs: A Retrospective Multi-center Study in Pharmacies in the Kojima Region, Okayama

Drug-drug interactions (DDIs) are responsible for an increase in the incidence of adverse drug reactions. Although CYP is known to be involved in metabolic processes, the DDIs among three or more drugs that involve the same CYP molecular species have not been fully investigated. In this study, we retrospectively examined the relationship between the number of drugs and potential DDIs in metabolic processes involving CYPs in patients who picked up their prescribed drugs at 11 pharmacies in the Kojima Branch of the Okayama Pharmaceutical Association. We found that 66.5% of the 924 patients had potential DDIs; more than half of the patients who took six or more drugs had potential DDIs among three or more drugs. The mean number of CYP3A4-related drugs involved in potential DDIs was 3.52±1.56 in patients who took seven drugs, suggesting the need for careful monitoring of specific symptoms and blood test results for the early detection of adverse drug reactions caused by DDIs among three or more drugs.