Challenge–dechallenge–rechallenge

Challenge–dechallenge–rechallenge (CDR) is a method used primarily in clinical pharmacology and drug safety to assess the relationship between a drug and an adverse event or side effect. It involves three key phases: 1. **Challenge**: This phase involves administering the drug to a patient and observing whether they experience the adverse effect. If a patient develops symptoms or a specific reaction after being given the drug, this establishes a potential initial connection between the drug and the adverse event.