title: The influence of CYP3A5 genotype on dexamethasone induction of CYP3A activity in African Americans.
abstract: The CYP3A5(*)1 allele has been associated with differences in the metabolism of some CYP3A substrates. CYP3A5 polymorphism may also influence susceptibility for certain drug interactions. We have previously noted a correlation between basal CYP3A activity and the inductive effects of dexamethasone using the erythromycin breath test (ERBT). To determine whether CYP3A5 polymorphism influences induction of CYP3A activity, we examined the effect of an antiemetic regimen of dexamethasone, and the prototypical inducer rifampin, on the ERBT in African American volunteers prospectively stratified by CYP3A5(*)1 allele carrier status. Mean basal ERBTs were significantly higher in CYP3A5(*)1 carriers (2.71 +/- 0.53%) versus noncarriers (2.12 +/- 0.37%, P = 0.006). Rifampin increased ERBTs in CYP3A5(*)1 carriers (4.68 versus 2.60%, P = 0.0008) and noncarriers (3.55 versus 2.11%, P = 0.0017), whereas dexamethasone increased ERBTs only in CYP3A5(*)1 noncarriers (3.03 versus 2.14%, P = 0.031). CYP3A5 polymorphism appears to influence susceptibility to induction-type drug interactions for some inducers, and CYP3A5(*)1 noncarriers may be more susceptible to the inductive effects of dexamethasone as a result of lower basal CYP3A activity.
authors.affiliation: Division of Pharmacotherapy and Experimental Therapeutics, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Roberts
authors.forename: Kristan D
authors.initials: KD
authors.lastname: Rollins
authors.forename: Angela D M
authors.initials: AD
authors.lastname: Kashuba
authors.forename: Mary F
authors.initials: MF
authors.lastname: Paine
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Nelsen
authors.forename: Eric E
authors.initials: EE
authors.lastname: Williams
authors.forename: Cassandra
authors.initials: C
authors.lastname: Moran
authors.forename: Jatinder K
authors.initials: JK
authors.lastname: Lamba
authors.forename: Erin G
authors.initials: EG
authors.lastname: Schuetz
authors.forename: Roy L
authors.initials: RL
authors.lastname: Hawke
mesh_terms: D000293:Adolescent; D000328:Adult; D044383:Black People; D051544:Cytochrome P-450 CYP3A / Q000096:biosynthesis* / Q000235:genetics; D003907:Dexamethasone / Q000494:pharmacology*; D004790:Enzyme Induction; D005838:Genotype; D006801:Humans; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D001741:Black or African American
chemical_list: D003907:Dexamethasone; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A