Warfarin has been on the drug market for approximately fifty years and has demonstrated its usefulness in thousands of studies in the United States and abroad.  Despite warfarin’s proven effectiveness, use of this drug is consistently found to be low especially in patients with chronic atrial fibrillation.  One study reported prescription of warfarin at hospital discharge in patients with atrial fibrillation was only 34%.⁽¹⁾   Under-utilization of this medication can impact the patient’s health as well as increase already rising health care costs.  The patient’s quality of life can diminish drastically if he/she suffers from atrial fibrillation induced stroke.  In addition, the health care system becomes burdened with an increase in hospital admissions, increased length of stay in the hospital and an increased mortality rate. 

     Atrial fibrillation causes 45% of all strokes, with risk becoming even greater as age increases.⁽²⁾  People with atrial fibrillation are more at risk for strokes due to blood not being properly pumped out of the heart.  If blood becomes stagnant, a clot can form.  If a clot is pumped out of the heart, it travels up to the brain and causes a stroke.  Warfarin is used to prevent clots from forming.   In many clinical trials, warfarin has shown benefit to patients with atrial fibrillation by reducing risk of stroke by two-thirds.⁽³⁾  If this is a proven fact, then why is warfarin still being underused?

     There is much speculation as to the reasons for warfarin under-use.  Some are patient related factors such as advanced age, non-compliance, fear of bleeding, theory of rat poison (see rat poison link on this website), and alcoholism.  The elderly population is one group in which warfarin is often not prescribed.  Physicians feel elderly people are more at risk for bleeding complications and are harder to manage because they are more sensitive to the drug.  Alcoholics are also a group of patients in which warfarin monitoring becomes difficult.  Alcohol can increase the INR and the liver problems it causes can make monitoring therapy difficult because the liver is where warfarin is broken down. 

     There are also physician related factors, which limit the use of warfarin.  Each physician has his/her own beliefs as to what the risks vs. benefits are when considering warfarin therapy.  There is no clear cut standard as to when a physician should initiate therapy or not.  This creates an inconsistency in prescribing habits.  Some factors known to sway a physician’s decision are past experiences with the drug, fear of litigation, and fear of causing bleeding in the patient.  Some other issues brought up by physicians were the amount of monitoring time needed to maintain proper anticoagulation and also the relevance of the clinical studies to actual practice.  Many physicians feel the efficacy of warfarin in clinical trials is due to the strict monitoring of INR’s and patient compliance with the drug.⁽⁴⁾   In real life practice, it is impossible to monitor patients so closely.

     One study recently published looks into this problem in more depth.  The investigators were looking for the actual use of warfarin in atrial fibrillation patients at hospital discharge, factors associated with warfarin under-use, and the association between the prescription of warfarin and the occurrence of adverse outcomes in those patients.  They were able to look at 597 atrial fibrillation patients.  They found 34% were discharged on warfarin, 21% were discharged on aspirin, and 45% were discharged on no therapy. 

     They found several groups of patients in which warfarin therapy was more likely to be underused.  If the patients were greater than 76 years old, female, in a rural setting, had recent surgery or trauma, had a history of bleeding, or had renal or hepatic disease they were less likely to receive warfarin.⁽⁵⁾   Some of these underused categories are a bit mesmerizing.  Females have been shown in many clinical trials to benefit more than men, however in actual practice they are less likely to receive warfarin.^(6,7,8)  Also, my experience in clinic has led me to believe patients who are greater than 76 years old do just as well as any other age group if they are managed appropriately.

     The investigators concluded patients were less likely to have an adverse outcome such as stroke if they were prescribed warfarin therapy.  Warfarin reduced the risk of stroke by 24%, whereas aspirin reduced the risk by only 5%.  They were able to cite two main reasons for warfarin under-use, inconvenience of monitoring the drug and physician fear of bleeding in their patients.⁽⁵⁾

       Knowing what physicians are thinking, we can now try to fix the problem at hand.  One of the best strategies is to put an expert in anticoagulation on the healthcare team.  Pharmacists have moved into a more clinical role these days.  They are willing to take on the monitoring roles that accompany many drugs of under-use. Pharmacists have the time to research the topic in great depth and can spend the time to monitor patients.  However, it is important to have good communication between pharmacists and physicians in order to keep all healthcare members on the same page. 

Editors Note:  I am adding some information which became available after this was written.

Devereaux et al ⁽¹⁰⁾ published an observational study about the differences in perspectives of physicians and patients concerning anticoagulation for atrial fibrillation.  They found that patients placed more value on avioding a stroke and less value on avoiding bleeding than physicians.  They recommend that the views of individual patients be given consideration when decisions are made about treatment.

REFERENCES

1)       Cohen N, Alon I, Gorelik O, et al.  Warfarin for Stroke Prevention Still Underused in Atrial Fibrillation.  Stroke. 2000; 31(6): 1217

2)      Becker, et al.  Antithrombotic, 1^st Edition, 2000.

3)      Connolly, Stuart. Anticoagulation for Patients with Atrial Fibrillation and Risk Factors for Stroke.  BMJ. 2000;320:1219-1220.

4)      Bungard, et al.  Why do Patients with Atrial Fibrillation Not Receive Warfarin? Arch Intern Med 160:41-46, Jan 10, 2000.

5)      Gage, et al. Adverse Outcomes and Predictors of Underuse of Antithrombotic Therapy in Medicare Beneficiaries with Chronic Atrial Fibrillation.  Stroke.  31:822-827, 2000.

6)      National Stroke Association.  The Stroke Prevention in Atrial Fibrillation III Study: Rationale, Design, and Patient Features.  Journal of Stroke and Cerebrovascular Diseases.  6(5):341, 1997.

7)      McBride, Ruth.  Adjusted-dose Warfarin versus Low-intensity, Fixed Dose Warfarin Plus Aspirin for High-risk Patients with Atrial Fibrillation: Stroke Prevention in Atrial Fibrillation III Randomized Clinical Trial.  The Lancet.  Vol348, Sept. 7, 1996.

8)      The SPAF III Writing Committee for the Stroke Prevention in Atrial Fibrillation Investigators.  Patients with Nonvalvular Atrial Fibrillation at Low Risk of Stroke During Treatment with Aspirin. JAMA. 279(16); Apr 1998.

9)      Lodwick, Al.  The Legend of Warfarin.  URL:http://warfarinfo.com/rat-poison.htm.

10) Devereaux PJ et al. Differences between perspectives of physicians and patients on anticoagulation in patients with atrial fibrillation:observational study. BMJ 2001;323:1218

 

 

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Last modified August 29, 2004