title: Erlotinib and pantoprazole: a relevant interaction or not?
abstract: OBJECTIVE
  There is increasing evidence that erlotinib exposure correlates well with treatment outcome. In this report we present a case of therapeutic drug monitoring of erlotinib in a patient with a gastric ulcer, treated with the proton pump inhibitor pantoprazole. This agent may cause an unwanted, but not always unavoidable, interaction since absorption of erlotinib is pH dependent.
  
  
  METHODS
  Erlotinib trough concentrations were monitored in a patient during treatment with orally and intravenously administered pantoprazole.
  
  
  RESULTS
  Erlotinib trough concentrations were diminished during high dose intravenously administered pantoprazole, but returned to normal when the dose was reduced and pantoprazole was administered orally.
  
  
  CONCLUSIONS
  More studies are needed to assess the dose dependency of the interaction between pantoprazole and erlotinib. Furthermore, we advise to monitor closely erlotinib plasma concentrations and adjust the erlotinib dose accordingly when a clinically relevant interaction is suspected and no proper dosing guidelines are available.
authors.affiliation: Department of Pharmacy, Meander Medical Center, Amersfoort, the Netherlands. rob@terheine.nl
authors.forename: Rob
authors.initials: R
authors.lastname: Ter Heine
authors.forename: James C
authors.initials: JC
authors.lastname: Fanggiday
authors.forename: Nienke A G
authors.initials: NA
authors.lastname: Lankheet
authors.forename: Jos H
authors.initials: JH
authors.lastname: Beijnen
authors.forename: Monique M L
authors.initials: MM
authors.lastname: Van Der Westerlaken
authors.forename: Gerald H A
authors.initials: GH
authors.lastname: Staaks
authors.forename: Mirte M
authors.initials: MM
authors.lastname: Malingré
mesh_terms: D053799:2-Pyridinylmethylsulfinylbenzimidazoles / Q000008:administration & dosage / Q000494:pharmacology*; D000897:Anti-Ulcer Agents / Q000008:administration & dosage / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000097:blood / Q000494:pharmacology*; D002289:Carcinoma, Non-Small-Cell Lung / Q000097:blood / Q000188:drug therapy; D004334:Drug Administration Schedule; D004347:Drug Interactions; D000069347:Erlotinib Hydrochloride; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000097:blood / Q000188:drug therapy; D008875:Middle Aged; D000077402:Pantoprazole; D054328:Proton Pump Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D011799:Quinazolines / Q000097:blood / Q000494:pharmacology*
chemical_list: D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D000897:Anti-Ulcer Agents; D000970:Antineoplastic Agents; D054328:Proton Pump Inhibitors; D011799:Quinazolines; D000077402:Pantoprazole; D000069347:Erlotinib Hydrochloride