0
Clinical Investigations: CARDIOLOGY |

Warfarin Maintenance Dosing Patterns in Clinical Practice*: Implications for Safer Anticoagulation in the Elderly Population

David Garcia, MD; Susan Regan, PhD; Mark Crowther, MD, MSc; Robert A. Hughes, MD; Elaine M. Hylek, MD, MPH
Author and Funding Information

Affiliations: *From the Department of Medicine (Dr. Garcia), Division of General Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM; the Department of Medicine (Drs. Regan and Hughes), General Medicine Division, Massachusetts General Hospital, Harvard Medical School, Boston, MA; the Department of Medicine (Dr. Crowther), McMaster University, Hamilton, ON, Canada; and the Department of Medicine (Dr. Hylek), General Internal Medicine Research Unit, Boston University School of Medicine, Boston, MA.,  A list of practices and directors that participated in the study is located in the Appendix.

Correspondence to: David A. Garcia, MD, Department of Internal Medicine, MSC10 5550, Albuquerque, NM 87131; e-mail: davgarcia@salud.unm.edu



Chest. 2005;127(6):2049-2056. doi:10.1378/chest.127.6.2049
Text Size: A A A
Published online

Background: The use of anticoagulant therapy is expanding among the elderly population, in part because of the increasing prevalence of atrial fibrillation. Published data describing the warfarin maintenance dose requirements for this age group are limited. Because warfarin therapy is often initiated in the outpatient setting where significant barriers to daily monitoring exist for this patient population, a better understanding of the factors that predict lower dose requirements may reduce the risk of unanticipated overanticoagulation and hemorrhage.

Objective: To define the effects of age and gender on the warfarin maintenance dose among ambulatory adult patients with an international normalized ratio target between 2.0 and 3.0.

Design: Prospective cohort study and retrospective cohort secondary data source.

Setting: One hundred one community-based physician practices with dedicated warfarin management systems and an academic medical center anticoagulation clinic.

Patients: A total of 4,616 patients comprised the prospective cohort, and 7,586 patients comprised the retrospective cohort. Of the 12,202 patients, 2,359 were ≥ 80 years of age.

Measurements: Median weekly and daily maintenance warfarin dose.

Results: The warfarin dose was inversely related to age and was strongly associated with gender. The median weekly dose ranged from 45 mg (6.4 mg/d) for men who were < 50 years of age to 22 mg (3.1 mg/d) for women ≥ 80 years of age. The weekly dose declined by 0.4 mg/yr (95% confidence interval [CI], 0.37 to 0.44; p < 0.001) and women required 4.5 mg less per week than men (95% CI, 3.8 to 5.3; p < 0.001). Among patients who were > 70 years of age, the often-suggested initiation dose of 5 mg/d will be excessive for 82% of women and 65% of men.

Conclusions: Warfarin dose requirements decrease greatly with age. Older women require the lowest warfarin doses. These observations suggest that, when warfarin is being initiated, the commonly employed empiric starting dose of 5 mg/d will lead to overanticoagulation for the majority of patients in the geriatric age group; lower initiation and maintenance doses should be considered for the elderly.

Figures in this Article

Sign In to Access Full Content

MEMBER & INDIVIDUAL SUBSCRIBER

Want Access?

NEW TO CHEST?

Become a CHEST member and receive a FREE subscription as a benefit of membership.

Individuals can purchase this article on ScienceDirect.

Individuals can purchase a subscription to the journal.

Individuals can purchase a subscription to the journal or buy individual articles.

Learn more about membership or Purchase a Full Subscription.

INSTITUTIONAL ACCESS

Institutional access is now available through ScienceDirect and can be purchased at myelsevier.com.

Sign In to Access Full Content

MEMBER & INDIVIDUAL SUBSCRIBER

Want Access?

NEW TO CHEST?

Become a CHEST member and receive a FREE subscription as a benefit of membership.

Individuals can purchase this article on ScienceDirect.

Individuals can purchase a subscription to the journal.

Individuals can purchase a subscription to the journal or buy individual articles.

Learn more about membership or Purchase a Full Subscription.

INSTITUTIONAL ACCESS

Institutional access is now available through ScienceDirect and can be purchased at myelsevier.com.

Figures

Tables

References

NOTE:
Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Sign In to Access Full Content

MEMBER & INDIVIDUAL SUBSCRIBER

Want Access?

NEW TO CHEST?

Become a CHEST member and receive a FREE subscription as a benefit of membership.

Individuals can purchase this article on ScienceDirect.

Individuals can purchase a subscription to the journal.

Individuals can purchase a subscription to the journal or buy individual articles.

Learn more about membership or Purchase a Full Subscription.

INSTITUTIONAL ACCESS

Institutional access is now available through ScienceDirect and can be purchased at myelsevier.com.

Related Content

Customize your page view by dragging & repositioning the boxes below.

Find Similar Articles
CHEST Journal Articles
PubMed Articles
  • CHEST Journal
    Print ISSN: 0012-3692
    Online ISSN: 1931-3543