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Interindividual variability in drug response remains a major challenge in clinical therapy, with outcomes ranging from treatment failure to serious adverse drug reactions. A significant proportion of this variability arises from differences in drug metabolism, much of which is governed by the cytochrome P450 (CYP) enzyme system. Predominantly expressed in hepatocytes, CYP enzymes catalyze the biotransformation and clearance of a wide array of xenobiotics and potentially toxic compounds. Although these enzymes participate in essential physiological processes, including steroid and hormone synthesis, metabolism of fat-soluble vitamins, and regulation of fatty acids, their most critical impact lies in pharmacokinetics and drug metabolism. A relatively small subset of CYP isoforms accounts for the majority of drug-processing activity, with CYP family enzymes collectively involved in an estimated 80% to 90% of enzymatic drug metabolism.[1] Because drugs can either influence CYP activity or be influenced by it, unintended interactions may arise, altering therapeutic efficacy or increasing toxicity. Understanding how drugs modulate CYP enzymes and how genetic, environmental, and pharmacological factors shape CYP function is essential for optimizing therapy and ensuring safe, effective clinical outcomes.[2]

Inflammatory states significantly influence CYP enzyme expression and activity. Hepatic diseases such as cirrhosis, characterized by progressive fibrosis and hepatocellular loss, markedly reduce metabolic capacity due to impaired hepatocyte function. The clinical manifestations of cirrhosis are closely linked to these metabolic disturbances. Altered steroid hormone metabolism, partly mediated by disrupted CYP-dependent steroidogenic pathways, contributes to the development of gynecomastia, spider angiomas, and other endocrine abnormalities commonly observed in patients with cirrhosis.[16] In addition to reduced CYP activity, cirrhosis is associated with diminished hepatic synthesis of plasma proteins, including albumin, which further impacts drug distribution and free drug concentrations.[17] Because CYP enzymes are also expressed in the intestinal epithelium, disorders affecting the small or large bowel can alter presystemic metabolism and oral drug bioavailability. Although intestinal CYP enzymes contribute only modestly to overall xenobiotic metabolism compared to hepatic CYPs, their role in first-pass metabolism and absorption is clinically significant. Disease-related changes or concurrent exposures may therefore reduce or enhance systemic drug levels. Grapefruit juice is a well-known example of such interactions: its flavonoid component, naringin, inhibits intestinal CYP3A4, decreasing enterocyte-mediated metabolism and increasing systemic concentrations of CYP3A4 substrates even at relatively small ingested amounts.[6] Infectious and inflammatory conditions further modulate CYP activity through cytokine-mediated downregulation. Interleukins, interferons, tumor necrosis factor, and other inflammatory mediators suppress the transcription and activity of multiple CYP isoforms.[3] This immune-driven reduction in metabolic capacity underscores the broader role of inflammation in altering pharmacokinetics during both localized and systemic infections.