[Warfarin treatment and bleeding].
BACKGROUND
Warfarin is involved in the majority of fatal adverse drug events in Norway. The aim of this study is to identify risk factors behind the haemorrhagic complications.


METHODS
We analysed all adverse event reports involving bleeding related to warfarin that were received by the Norwegian Medicines Agency from 1990 to 2000.


RESULTS
713 reports were included; 71% of the patients were above 70 years of age. The most frequent diagnosis was atrial fibrillation (39%). Cerebral bleedings were reported in 57% of the cases, 73% of which were fatal, as were 39 % of gastrointestinal bleedings and 14% of other bleedings. International normalised ratio values (INR values) at the time of bleeding were reported in 83% of the cases; mean INR value was 4.4 (range 1.2 - > 8.0). INR values above recommended limits at the time of bleeding were found in 74% of the patients. In 63%, bleedings occurred during the first month; in 30% during the first five days. Median duration of treatment was shorter in fatal (16 days) than in non-fatal cases (24 days).


CONCLUSIONS
Our results show that haemorrhagic complications are associated with high INR values and initiation of treatment. Simple strategies for reducing bleedings include better monitoring of patients, careful dose adjustment, and INR values in the lower end of the recommended ranges.
Breen
Anne Berg
AB
Institutt for farmakoterapi, Det medisinske fakultet, Universitetet i Oslo, Postboks 1065 Blindern, 0316 Oslo.
Vaskinn
Trine Elise
TE
Reikvam
Asmund
A
Skovlund
Eva
E
Lislevand
Harald
H
Madsen
Steinar
S
D000328:Adult; D016907:Adverse Drug Reaction Reporting Systems; D000368:Aged; D000925:Anticoagulants / Q000009:adverse effects*; D002543:Cerebral Hemorrhage / Q000139:chemically induced; D005260:Female; D006471:Gastrointestinal Hemorrhage / Q000139:chemically induced; D006470:Hemorrhage / Q000139:chemically induced*; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D014859:Warfarin / Q000009:adverse effects*
D000925:Anticoagulants; D014859:Warfarin