title: Induction of CYP3A4 by efavirenz in primary human hepatocytes: comparison with rifampin and phenobarbital.
abstract: The antiretroviral agent efavirenz enhances the systemic clearance of coadministered drugs that are cytochrome P450 (CYP) 3A4 substrates. The mechanism of the apparent increase in CYP3A4 activity by efavirenz and the magnitude of change relative to other known inducers are not known. The authors tested the hypothesis that increased enzymatic activity by efavirenz entails CYP3A4 induction and activation of the human pregnane X receptor (hPXR), a key transcriptional regulator of CYP3A4. Employing primary cultures of human hepatocytes, they compared the CYP3A4 inductive effects of efavirenz (1-10 microM) to rifampin (10 microM) and phenobarbital (2 mM). A cell-based reporter assay was employed to assess hPXR activation. The authors observed that efavirenz caused a concentration-dependent CYP3A4 induction and hPXR activation. Based on the CYP3A4 activity assay, the average magnitude of induction by efavirenz (5-10 microM) was approximately 3- to 4-fold. In comparison, phenobarbital (2 mM) and rifampin (10 microM) caused a 5- and 6-fold induction, respectively.
authors.affiliation: College of Pharmacy, University of Cincinnati Medical Center, 3223 Eden Avenue, Mail Location #0004, Cincinnati, OH 45267, USA.
authors.forename: Niresh
authors.initials: N
authors.lastname: Hariparsad
authors.forename: Srikanth C
authors.initials: SC
authors.lastname: Nallani
authors.forename: Rucha S
authors.initials: RS
authors.lastname: Sane
authors.forename: Donna J
authors.initials: DJ
authors.lastname: Buckley
authors.forename: Arthur R
authors.initials: AR
authors.lastname: Buckley
authors.forename: Pankaj B
authors.initials: PB
authors.lastname: Desai
mesh_terms: D000480:Alkynes; D019380:Anti-HIV Agents / Q000494:pharmacology*; D048588:Benzoxazines; D002478:Cells, Cultured; D003521:Cyclopropanes; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D010078:Oxazines / Q000494:pharmacology*; D010634:Phenobarbital / Q000494:pharmacology*; D000077297:Pregnane X Receptor; D012333:RNA, Messenger / Q000096:biosynthesis; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists; D011987:Receptors, Steroid / Q000819:agonists; D012293:Rifampin / Q000494:pharmacology*
chemical_list: D000480:Alkynes; D019380:Anti-HIV Agents; D048588:Benzoxazines; D003521:Cyclopropanes; D010078:Oxazines; D000077297:Pregnane X Receptor; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; C098320:efavirenz; D012293:Rifampin; D010634:Phenobarbital