title: Impact of co-administered drugs on drug monitoring of capecitabine in patients with advanced colorectal cancer.
abstract: BACKGROUND
  Drug monitoring is a useful tool for obtaining detailed information about the disposition of a drug in an individual patient during chemotherapy. According to the international guidelines, the analytical assay for quantification of a compound in biological samples must be validated. Among a number of parameters, peak purity is an important requirement.
  
  
  METHODS
  We analyzed pharmacokinetics in patients who received chemotherapy with capecitabine and up to 10 various co-medications.
  
  
  RESULTS
  Out of seven investigated co-administered drugs, we found evidence that the proton pump inhibitor pantoprazole causes peak interferences with capecitabine during high-performance liquid chromatography analysis. Therefore quantification of capecitabine in plasma samples can be inaccurate.
  
  
  CONCLUSIONS
  We recommend an altered time schedule for co-administered drugs or changing the mobile phase used in the assay.
authors: Department of Clinical Pharmacy and Diagnostics, University of Vienna, Vienna, Austria veronika.schreiber@univie.ac.at.
authors: Veronika
authors: V
authors: Schreiber
authors: Department of Clinical Pharmacy and Diagnostics, University of Vienna, Vienna, Austria.
authors: Marie
authors: M
authors: Kitzmueller
authors: Department of Clinical Pharmacy and Diagnostics, University of Vienna, Vienna, Austria.
authors: Martina
authors: M
authors: Poxhofer
authors: Department of Clinical Pharmacy and Diagnostics, University of Vienna, Vienna, Austria.
authors: Stefanie
authors: S
authors: Gintersdorfer
authors: Department of Drug and Natural Product Synthesis, University of Vienna, Vienna, Austria.
authors: Catharina
authors: C
authors: Neudorfer
authors: Center for Social Medicine, Kaiser Franz-Josef Hospital with Gottfried von Preyer Pediatric Hospital, Hospital Pharmacy, Vienna, Austria.
authors: Maria
authors: M
authors: Lichtneckert
authors: Center for Social Medicine, Kaiser Franz-Josef Hospital with Gottfried von Preyer Pediatric Hospital, Hospital Pharmacy, Vienna, Austria.
authors: Christian
authors: C
authors: Dittrich
authors: Department of Clinical Pharmacy and Diagnostics, University of Vienna, Vienna, Austria Austrian Society of Applied Pharmacokinetics, Vienna, Austria.
authors: Martin
authors: M
authors: Czejka
mesh_terms: D053799:2-Pyridinylmethylsulfinylbenzimidazoles / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics; D000069287:Capecitabine; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D015179:Colorectal Neoplasms / Q000097:blood* / Q000188:drug therapy*; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics; D004334:Drug Administration Schedule; D004347:Drug Interactions; D016903:Drug Monitoring / Q000379:methods*; D005467:Floxuridine / Q000097:blood*; D005472:Fluorouracil / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics; D006801:Humans; D000077402:Pantoprazole; D054328:Proton Pump Inhibitors / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics
chemical_list: D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D054328:Proton Pump Inhibitors; D005467:Floxuridine; D003841:Deoxycytidine; D000069287:Capecitabine; C418208:5'-deoxy-5-fluorocytidine; D000077402:Pantoprazole; D005472:Fluorouracil; C025034:doxifluridine
keywords: Capecitabine; HPLC; interaction; metabolites; pantoprazole; premedication