Dechallenge

Dechallenge is a method used in pharmacovigilance and clinical toxicology in which a patient stops taking a suspected drug to see if an adverse reaction improves or resolves. The aim is to help determine whether the drug is likely responsible for the observed effect.

In practice, the suspected medication is withdrawn or its dose reduced, and the patient is monitored for changes in symptoms, signs, and laboratory abnormalities. A positive dechallenge occurs when the adverse event diminishes after withdrawal, supporting a causal link between the drug and the reaction. A partial or absent improvement may indicate a less clear relationship or influence by other factors. The time course of improvement depends on the drug’s pharmacokinetics and the nature of the adverse event.

Limitations include the possibility that symptoms improve for reasons unrelated to withdrawal, such as spontaneous resolution or concurrent treatments. Ethical or clinical concerns may limit the ability to perform a dechallenge, especially if the reaction is severe. Dechallenge evidence is typically considered alongside other information and may be strengthened by rechallenge data or formal causality assessment tools.

Examples of dechallenge include cessation of a medication associated with a rash or liver enzyme elevation, followed by noticeable improvement upon stopping the drug. See also areas such as adverse drug reaction, rechallenge, and causality assessment in pharmacovigilance.