Assessment of Consistency of Drug Interaction Information in Drug Labels Among the United States, the United Kingdom, China, Japan, and Korea.

Information gap in drug labeling among countries create challenges in therapeutic use of drugs. We aimed to evaluate the consistency of drug interaction information in drug labels among five countries. The study drugs were chosen from the commonly approved drug list in the US, UK, China, Japan, and Korea. The degree of agreement of drug interaction data was evaluated by kappa coefficient. Thirty-eight drugs were evaluated, and moderate degree of agreement was observed among all countries' labeling (κ = 0.43, 95% confidence interval (CI) = 0.41-0.46). The degree of agreement was the highest for the UK and Korea (κ = 0.71, 95% CI = 0.67-0.75) and the lowest for the UK and Japan (κ = 0.02, 95% CI = 0.00-0.04). Information regarding drug interactions listed in the studied drug labels was not in high agreement. International standardization of drug labeling is required to ensure safe drug therapy.