Cytochromes P450, main enzymes of drug metabolism, play a prominent role in the first-pass metabolism of oral substances. Inter-individual variability in their activity due to genetic and environmental factors has been observed and may be associated with adverse therapeutic outcomes (ineffectiveness or toxicity). The inflammation, whether acute or chronic, can theoretically modulate the pharmacokinetics of drugs by modulating enzyme activity. Indeed, in vitro data and animal models, as well as more limited data in humans, indicate a down-regulation of CYP in the context of inflammation.