Drug-Drug Interaction (DDI) occurs when one drug changes the pharmacokinetics, safety profile, or clinical effect of another drug when taken together.
DDIs may increase toxicity, reduce efficacy, or alter exposure through metabolic or transporter-based mechanisms. In clinical trials, DDI assessment informs eligibility criteria, prohibited concomitant medications, dose adjustments, and safety monitoring requirements. Sponsors evaluate DDI risk during development to inform protocol safeguards and labeling strategy. Robust DDI planning supports participant protection and clearer informed consent risk disclosure.