Mechanism of hypersensitivity reactions: proposed involvement of reactive metabolites generated by activated leukocytes.

Hypersensitivity drug reactions are a major source of serious adverse drug reactions, yet very little is known about their mechanism. Several drugs are oxidized by activated neutrophils and mononuclear cells to reactive metabolites. Jack Uetrecht explains that the pattern of hypersensitivity reactions associated with these drugs - drug-induced lupus, agranulocytosis, and generalized hypersensitivity reactions - fits a mechanism in which leukocyte-generated reactive metabolites initiate the hypersensitivity reaction. Because activation of the leukocyte is necessary for reactive metabolite formation, one risk factor for a drug hypersensitivity reaction may be an infection or other inflammatory condition.