title: A kinetic and dynamic study of oral alprazolam with and without erythromycin in humans: in vivo evidence for the involvement of CYP3A4 in alprazolam metabolism.
abstract: OBJECTIVE
  To assess the possible involvement of CYP3A4 in the metabolism of alprazolam in vivo.
  
  
  METHODS
  Twelve healthy male volunteers were randomly allocated to one of the two different treatment sequences, placebo-erythromycin or erythromycin-placebo, with an at least 6-week washout period between the two trial phases. Each volunteer received 400 mg erythromycin or matched placebo given orally three times a day for 10 days and an oral dose (0.8 mg) of alprazolam on the posttreatment day 8. Plasma concentration of alprazolam was measured up to 48 hours after the administration, and psychomotor function was assessed at each time of blood samplings with use of the Digit Symbol Substitution Test, visual analog scale, and Udvalg for kliniske undersøgelser side effect rating scale.
  
  
  RESULTS
  Erythromycin significantly (p < 0.001) increased the area under the plasma concentration-time curves (200 +/- 43 versus 322 +/- 49 ng . hr/ml from 0 to 48 hours and 229 +/- 52 versus 566 +/- 161 ng . hr/ml from 0 hour to infinity), decreased the apparent oral clearance (1.02 +/- 0.31 versus 0.41 +/- 0.12 ml/min/kg), and prolonged the elimination half-life (16.0 +/- 4.5 versus 40.3 +/- 14.4 hours) of alprazolam. However, any psychomotor function variables did not differ significantly between the erythromycin and placebo trial phases.
  
  
  CONCLUSIONS
  This study suggests that erythromycin, an inhibitor of CYP3A4, inhibits the metabolism of alprazolam, providing an in vivo evidence for the involvement of CYP3A4 in its metabolism. However, the kinetic change of alprazolam by erythromycin does not result in the pharmacodynamic change of this triazolobenzodiazepine, at least after single dosing.
authors.affiliation: Department of Neuropsychiatry, Hirosaki University Hospital, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Yasui
authors.forename: K
authors.initials: K
authors.lastname: Otani
authors.forename: S
authors.initials: S
authors.lastname: Kaneko
authors.forename: T
authors.initials: T
authors.lastname: Ohkubo
authors.forename: T
authors.initials: T
authors.lastname: Osanai
authors.forename: K
authors.initials: K
authors.lastname: Sugawara
authors.forename: K
authors.initials: K
authors.lastname: Chiba
authors.forename: T
authors.initials: T
authors.lastname: Ishizaki
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000525:Alprazolam / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D014151:Anti-Anxiety Agents / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D002851:Chromatography, High Pressure Liquid; D018592:Cross-Over Studies; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004347:Drug Interactions; D004917:Erythromycin / Q000008:administration & dosage / Q000494:pharmacology*; D006207:Half-Life; D006801:Humans; D008297:Male; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D013223:Statistics as Topic
chemical_list: D014151:Anti-Anxiety Agents; D011500:Protein Synthesis Inhibitors; D004917:Erythromycin; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D000525:Alprazolam