Cerebral haemorrhage induced by warfarin - the influence of drug-drug interactions.
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.
Jönsson
Anna K
AK
Department of Clinical Pharmacology, University Hospital, Linköping, Sweden. anna.k.jonsson@lio.se
Spigset
Olav
O
Jacobsson
Ingela
I
Hägg
Staffan
S
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*
D000925:Anticoagulants; D014859:Warfarin