When two or more drugs are taken by the same patient, they can have an effect on each other’s activity, this is called drug–drug interactions (DDIs). Evaluation of the potential interactions of a drug is an integral part of drug development and the benefit–risk assessment of new treatments.

DDIs can either reduce or enhance the therapeutic or adverse effects of drugs by causing alterations in the pharmacokinetics or pharmacodynamics of drugs. If not accounted for, they can result in clinically relevant toxicity or treatment failure. The aim of DDI studies is to gain knowledge of how the drug in development affects the safety and efficacy of other medicines and vice versa.