title: High prevalence of unknown co-medication in hospitalised patients.
abstract: OBJECTIVE
  Co-medication unknown to the treating physician, including self-medication, may compromise drug safety by increasing the risk of duplicate therapy, drug interactions and adverse drug reactions that are not recognised as such. The aim of the current study was to estimate exposure to unknown co-medication during hospitalisation by performing an analytical screening for a broad range of drugs and drug classes in urine of patients admitted to a general internal medicine ward.
  
  
  METHODS
  Urine samples of 44 patients were analysed with REMEDiHS (high-performance liquid chromatography) and six different immunoassays. Positive results were compared with drug history and documented drug prescription. If appropriate, gas chromatographic-mass spectrometric confirmatory analyses were performed on drugs classified at least once as possible unknown co-medication.
  
  
  RESULTS
  Nine (20%) of the patients tested positive for a compound detected by two independent analytical methods and 18 (41%) for a compound detected by at least one analytical method. Unknown co-medication consisted mostly of analgesics, benzodiazepines or ranitidine.
  
  
  CONCLUSIONS
  At least one in five patients exhibits at least once during hospitalisation exposure to drugs not documented in the patient record, which may compromise patient safety.
authors.affiliation: Department of Internal Medicine VI, Clinical Pharmacology and Pharmacoepidemiology, Ruprecht-Karls-University, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Rieger
authors.forename: André
authors.initials: A
authors.lastname: Scholer
authors.forename: Isabelle
authors.initials: I
authors.lastname: Arnet
authors.forename: Frank T
authors.initials: FT
authors.lastname: Peters
authors.forename: Hans H
authors.initials: HH
authors.lastname: Maurer
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Walter-Sack
authors.forename: Walter E
authors.initials: WE
authors.lastname: Haefeli
authors.forename: Meret
authors.initials: M
authors.lastname: Martin-Facklam
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006207:Half-Life; D006760:Hospitalization; D006801:Humans; D008297:Male; D008875:Middle Aged; D004364:Pharmaceutical Preparations / Q000652:urine*; D017891:Pharmacoepidemiology; D010599:Pharmacokinetics; D015995:Prevalence; D012651:Self Medication / Q000706:statistics & numerical data*; D013557:Switzerland / Q000453:epidemiology
chemical_list: D004364:Pharmaceutical Preparations