3. Hepatotoxicity associated to drugs

### 3.1. Expression of hepatotoxicity

Hepatotoxicity induced by drugs or toxins can be grouped into two types: intrinsic reactions (less common) and idiosyncratic reactions (more common) [6, 7, 26]. Intrinsic reactions are predictable, dose-dependent and reproducible in animal models; injury is produced trough toxic metabolites of drugs such as free radicals (generating lipid peroxidation), electrophilic molecules (formation of covalent bonds with hepatic proteins) or active oxygen molecules (generating peroxidation as well). Idiosyncratic reactions are not predictable, not dosedependent and not reproducible in animals; there are many drugs capable of causing this type of reaction [11, 27]. The underlying mechanism of the idiosyncratic reaction may be a genetic polymorphism of the cytochrome P450 (CYP450) system, responsible for the drugs hepatic biotransformation. There are two types of idiosyncratic reactions: immune (characterized by hypersensitivity-type reaction) and metabolic [7, 13] (related to metabolism of substances).
