title: Cerebral haemorrhage induced by warfarin - the influence of drug-drug interactions.
abstract: OBJECTIVE
  To evaluate the frequency, severity and preventability of warfarin-induced cerebral haemorrhages due to warfarin and warfarin-drug interactions in patients living in the county of Ostergötland, Sweden.
  
  
  METHODS
  All patients with a diagnosed cerebral haemorrhage at three hospitals during the period 2000-2002 were identified. Medical records were studied retrospectively to evaluate whether warfarin and warfarin-drug interactions could have caused the cerebral haemorrhage. The proportion of possibly avoidable cases due to drug interactions was estimated.
  
  
  RESULTS
  Among 593 patients with cerebral haemorrhage, 59 (10%) were assessed as related to warfarin treatment. This imply an incidence of 1.7/100,000 treatment years. Of the 59 cases, 26 (44%) had a fatal outcome, compared to 136 (25%) among the non-warfarin patients (p < 0.01). A warfarin-drug interaction could have contributed to the haemorrhage in 24 (41%) of the warfarin patients and in 7 of these (12%) the bleeding complication was considered being possible to avoid.
  
  
  CONCLUSIONS
  Warfarin-induced cerebral haemorrhages are a major clinical problem with a high fatality rate. Almost half of the cases was related to a warfarin-drug interaction. A significant proportion of warfarin-related cerebral haemorrhages might have been prevented if greater caution had been taken when prescribing drugs known to interact with warfarin.
authors.affiliation: Department of Clinical Pharmacology, University Hospital, Linköping, Sweden. anna.k.jonsson@lio.se
authors.forename: Anna K
authors.initials: AK
authors.lastname: Jönsson
authors.forename: Olav
authors.initials: O
authors.lastname: Spigset
authors.forename: Ingela
authors.initials: I
authors.lastname: Jacobsson
authors.forename: Staffan
authors.initials: S
authors.lastname: Hägg
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000009:adverse effects*; D002543:Cerebral Hemorrhage / Q000139:chemically induced* / Q000401:mortality / Q000517:prevention & control; D002648:Child; D004347:Drug Interactions; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010818:Practice Patterns, Physicians'; D012189:Retrospective Studies; D013548:Sweden / Q000453:epidemiology; D014859:Warfarin / Q000009:adverse effects*
chemical_list: D000925:Anticoagulants; D014859:Warfarin