Thromb Haemost 2001; 86(02): 569-574
DOI: 10.1055/s-0037-1616088
Review Article
Schattauer GmbH

Characteristics of Anticoagulant Therapy and Comorbidity Related to Overanticoagulation

Fernie J. A. Penning-van Beest
1   Pharmaco-epidemiology Unit, Departments of Internal Medicine and Epidemiology & Biostatistics, Erasmus University Medical Center, Rotterdam
,
Erik van Meegen
2   Red Cross Anticoagulation Clinic, The Hague
,
Frits R. Rosendaal
3   Hemostasis and Thrombosis Research Center, Department of Clinical Epidemiology, Leiden University Medical Center
,
Bruno H. Ch. Stricker
1   Pharmaco-epidemiology Unit, Departments of Internal Medicine and Epidemiology & Biostatistics, Erasmus University Medical Center, Rotterdam
4   Drug Safety Unit, Inspectorate for Health Care, The Hague, The Netherlands
› Author Affiliations
Further Information

Publication History

Received 05 December 2000

Accepted after resubmission 20 January 2001

Publication Date:
12 December 2017 (online)

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Summary

The risk of hemorrhage when using coumarin anticoagulants sharply increases when the International Normalised Ratio (INR) is ≥6.0. We performed a prospective cohort study with a nested case-control design among 17,056 outpatients of an anticoagulation clinic to determine the incidence of overanticoagulation and to study the association between overanticoagulation and characteristics of anticoagulant therapy and comorbidity. The incidence rate of an INR ≥6.0 was 7.8 per 10,000 treatment days in prevalent users on the starting date and 22.5 per 10,000 treatment days in incident users during the study period. 300 cases with an INR ≥6.0 were compared with 302 randomly selected matched controls with an INR within the target zone. Patients on acenocoumarol had an increased risk of an INR ≥6.0 compared to patients on phenprocoumon. Regarding comorbidity, impaired liver function, congestive heart failure, diarrhea and fever were risk factors for overanticoagulation. Increased monitoring of INR values if risk factors are present or avoidance of risk factors could prevent excess anticoagulation and potential bleeding complications.