The mechanisms by which IADRs occur are not clear. Evidence from experimental animals indicates that mild inflammation can decrease the threshold for toxicity and thereby render an individual susceptible to an adverse drug reaction that would not otherwise occur . Lipopolysaccharide (LPS), a cell wall component of gram-negative bacteria, is widely used as an inflammagen in these animal studies. A nonhepatotoxic dose of LPS can interact with nontoxic doses of several IADR-associated drugs from different pharmacologic classes to induce liver damage in rodents (Deng et al., 2006; Luyendyk et al., 2003; Waring et al., 2006; Zou et al., 2009b) .