Drugs That Cause a Deficiency of Vitamin K Clotting Factors

itored by anticoagulant clinics and diets need to be modified to compensate for the loss of vitamin K activity. Additionally, there is a long list of drugs that may interfere with vitamin K activity and subsequent hemo-stasis (Table 17.2).

If a patient is vitamin K depleted, the PT and aPTT will most likely be elevated but able to be corrected by normal plasma. Factor assays of the specific vitamin K factors will reveal a depressed activity. Factor VII with the shortest half-life will be depleted first within 2 days; the other factors will take between 3 and 10 days to reach low hemostatic levels. With mild bleeding, oral administration of vitamin K provides hemostatic recovery within a couple of hours. More emergent bleeding situations may result in parenteral administration of vitamin K, blood products, or infusion of prothrombin concentrate complex. An interesting side note is reports of patients who have used coumadin as an agent of suicide.14

Acquired inhibitors of coagulation will be discussed in Chapter 19.

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