title: Effect of erythromycin on metabolism of quetiapine in Chinese suffering from schizophrenia.
abstract: OBJECTIVE
  To study the effect of erythromycin on metabolism of quetiapine in Chinese suffering from schizophrenia.
  
  
  METHODS
  Nineteen patients received multiple doses of quetiapine (200 mg, twice daily) with or without co-administered erythromycin (500 mg, three times daily). Blood samples were collected at specified time intervals for determination of plasma concentrations of quetiapine and some of its metabolites.
  
  
  RESULTS
  With erythromycin co-administration: for quetiapine, maximal plasma concentration (Cmax), area under concentration-time curve of 0-infinity h (AUC0-infinity) and terminal-phase elimination half-life time (t1/2) increased 68, 129 and 92%, respectively, and clearance (CL) and terminal elimination rate constant (Ke) decreased 52% and 55%, respectively; for quetiapine sulfoxide (QTP-SF), Cmax, AUC0-infinity and AUC ratio decreased 64, 23, and 70%, respectively, and t1/2 increased 211%; for 7-hydroxy-quetiapine (QTP-H), Ke and AUC ratio decreased 61% and 45%, respectively, and t1/2 increased 203%; for 7-hydroxy-N-desalkyl-quetiapine (QTP-ND), Cmax, AUC0-infinity and AUC ratio decreased 36, 40 and 71%, respectively.
  
  
  CONCLUSIONS
  Erythromycin has a noticeable effect on the metabolism of quetiapine. When quetiapine is co-administered with CYP3A inhibitors such as erythromycin, the dosing regimen should be modified according to quetiapine TDM.
authors.affiliation: Clinical Pharmaceutical Research Institute, Hunan Provincial Tumor Hospital of China, Changsha, China.
authors.forename: Kun-Yan
authors.initials: KY
authors.lastname: Li
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.forename: Ze-Neng
authors.initials: ZN
authors.lastname: Cheng
authors.forename: Bi-Kui
authors.initials: BK
authors.lastname: Zhang
authors.forename: Wen-Xing
authors.initials: WX
authors.lastname: Peng
authors.forename: Huan-De
authors.initials: HD
authors.lastname: Li
mesh_terms: D000293:Adolescent; D000328:Adult; D014150:Antipsychotic Agents / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D019540:Area Under Curve; D044466:Asian People; D002851:Chromatography, High Pressure Liquid; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003987:Dibenzothiazepines / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D004917:Erythromycin / Q000494:pharmacology*; D005260:Female; D006207:Half-Life; D006801:Humans; D008297:Male; D008657:Metabolic Clearance Rate / Q000187:drug effects; D008875:Middle Aged; D000069348:Quetiapine Fumarate; D012559:Schizophrenia / Q000188:drug therapy* / Q000201:enzymology / Q000378:metabolism
chemical_list: D014150:Antipsychotic Agents; D003987:Dibenzothiazepines; D000069348:Quetiapine Fumarate; D004917:Erythromycin; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A