LETTER
Managing Anticoagulation Safely
Paulette Ginier;
Donald Tayloe; and
Suzanne Venturino
1 November 1993 | Volume 119 Issue 9 | Page 957
In their recent article, Fihn and coworkers [1] state that because they found no seasonal variation in complication rate, ingestion of vegetables rich in vitamin K has little effect on the variability in prothrombin time ratio (PTR) [1]. However, three of the five study sites were on the West Coast where cruciferous vegetables are available year-round. In a similar setting (that is, an anticoagulation clinic with a defined protocol and an experienced practitioner), it is not uncommon, despite dietary instruction, for patients to have a subtherapeutic international normalized ratio (INR) that readily corrects when the vitamin-K content of their diet is re-evaluated.
In addition, generalizing their findings to other than academic anticoagulation clinic settings is misleading. In our institution, inexperienced housestaff and other physicians often prescribe potentially interfering medications to patients receiving warfarin therapy. Many times, complications are avoided because the interfering drugs are stopped by the anticoagulation clinic.
To discount diet and interfering drugs as causes of the variability in PTR might be sending the wrong message. Diet and interfering drugs must be considered when treating and educating patients requiring anticoagulation therapy with warfarin. Management of long-term anticoagulation in the academic setting has been relegated to experienced practitioners with well-developed protocols. The knowledge and experience of persons working in anticoagulation clinics and the information in the anticoagulation clinic protocols need to be disseminated and shared with physicians in training and clinicians in other practice settings.
1. Fihn SD, McDonell M, Martin D, Henikoff J, Vermes D, Kent D, et al. Risk factors for complications of chronic anticoagulation: a multicenter study. Ann Intern Med. 1993; 118:511-20.
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