title: Differential effects of ethanol on spectral binding and inhibition of cytochrome P450 3A4 with eight protease inhibitors antiretroviral drugs.
abstract: BACKGROUND
  Cytochrome P450 3A4 (CYP3A4) is the most abundant CYP enzyme in the liver, which metabolizes approximately 50% of the marketed drugs including antiretroviral agents. CYP3A4 induction by ethanol and its impact on drug metabolism and toxicity is known. However, CYP3A4-ethanol physical interaction and its impact on drug binding, inhibition, or metabolism is not known, except that we have recently shown that ethanol facilitates the binding of a protease inhibitor (PI), nelfinavir, with CYP3A4. The current study was designed to examine the effect of ethanol on spectral binding and inhibition of CYP3A4 with all currently used PIs that differ in physicochemical properties.
  
  
  METHODS
  We performed type I and type II spectral binding with CYP3A4 at 0 and 20 mM ethanol and varying PIs' concentrations. We also performed CYP3A4 inhibition using 7-benzyloxy-4-trifluoromethylcoumarin substrate and NADPH at varying concentrations of PIs and ethanol.
  
  
  RESULTS
  Atazanavir, lopinavir, saquinavir, and tipranavir showed type I spectral binding, whereas indinavir and ritonavir showed type II. However, amprenavir and darunavir did not show spectral binding with CYP3A4. Ethanol at 20 mM decreased the maximum spectral change (δA(max)) with type I lopinavir and saquinavir, but it did not alter δA(max) with other PIs. Ethanol did not alter spectral binding affinity (K(D)) and inhibition constant (IC(50)) of type I PIs. However, ethanol significantly decreased the IC(50) of type II PIs, indinavir and ritonavir, and markedly increased the IC(50) of amprenavir and darunavir.
  
  
  CONCLUSIONS
  Overall, our results suggest that ethanol differentially alters the binding and inhibition of CYP3A4 with the PIs that have different physicochemical properties. This study has clinical relevance because alcohol has been shown to alter the response to antiretroviral drugs, including PIs, in HIV-1-infected individuals.
authors.affiliation: Division of Pharmacology and Toxicology, School of Pharmacy, University of Missouri-Kansas City, 64108, USA. kumarsa@umkc.edu
authors.forename: Santosh
authors.initials: S
authors.lastname: Kumar
authors.forename: Anil
authors.initials: A
authors.lastname: Kumar
mesh_terms: D044966:Anti-Retroviral Agents / Q000737:chemistry / Q000378:metabolism*; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism*; D065692:Cytochrome P-450 CYP3A Inhibitors; D000431:Ethanol / Q000494:pharmacology*; D006801:Humans; D011480:Protease Inhibitors / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D044966:Anti-Retroviral Agents; D065692:Cytochrome P-450 CYP3A Inhibitors; D011480:Protease Inhibitors; D000431:Ethanol; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human