Detailed Explanation
Dechallenge refers to the observation of what happens to an adverse event when the suspected causative drug is withdrawn or its dose reduced. A positive dechallenge occurs when the adverse event resolves or substantially improves following drug discontinuation, providing evidence supporting a causal relationship. A negative dechallenge, where the event persists despite drug withdrawal, suggests that other factors may be responsible, though it does not definitively exclude drug causality, particularly for reactions with long recovery times or irreversible effects.