According to ICH guidelines, which adverse drug reaction must be reported expeditiously?

The correct response highlights the need for rapid reporting of anaphylaxis that is not regarded as a listed side effect of the drug according to the ICH guidelines. Anaphylaxis is a severe and potentially life-threatening allergic reaction. When it occurs in association with a drug, particularly when it's unexpected or unlisted in the product's approved labeling, the urgency in reporting this reaction becomes paramount.

This is because ICH guidelines emphasize that serious adverse reactions, especially those that pose significant safety risks or are unforeseen, necessitate immediate attention and communication to regulatory authorities. Timely reporting can facilitate swift actions to manage safety risks, potentially leading to further investigation, the issuance of warnings, or modifications to drug labeling.

The other options reflect adverse reactions that are either mild or common side effects typically associated with drugs. While they still require monitoring, they do not carry the same immediate risk profile as anaphylaxis. Therefore, they do not meet the criteria for expeditious reporting under the ICH guidelines.