Rechallenge

Rechallenge refers to the deliberate re-exposure of an individual to a drug or other agent after a prior adverse reaction or after a period of discontinuation, with the aim of determining causality, restoring therapy, or assessing tolerance. In pharmacovigilance and clinical practice, rechallenge is considered when the benefits of the drug outweigh the risks or when alternatives are limited, and it should only be conducted under appropriate supervision.

In allergy and immunology, drug challenges are a common form of rechallenge used to confirm or exclude a suspected drug allergy, typically performed under controlled conditions. In other contexts, rechallenge may occur when a patient who previously tolerated a medication loses tolerance due to a change in state, or when a previously beneficial therapy is paused and later reintroduced.

Rechallenge can be performed as a graded or provocative challenge, beginning with a minimal exposure and gradually increasing, with continuous monitoring for adverse events. The decision to rechallenge depends on factors such as the severity and mechanism of the prior reaction (allergenic versus non-allergic), the necessity of the drug, availability of alternatives, and patient comorbidities. If the reaction recurs, the drug is usually avoided; in some cases, desensitization strategies may allow continued use.

In oncology and other fields, rechallenge can refer to reintroducing a previously used regimen after a period of interruption, sometimes as part of a broader strategy to maximize disease control. Data from rechallenge experiences contribute to pharmacovigilance databases and inform guidelines on drug safety and management of adverse reactions.