Vitamin K in anticoagulation therapy

Abstract

M Crowther and colleagues1Crowther MA Julian J McCarty D et al.Treatment of warfarin-associated coagulopathy with oral vitamin K: a randomised controlled trial.Lancet. 2000; 356: 1551-1553Summary Full Text Full Text PDF PubMed Scopus (164) Google Scholar show that vitamin K lowers the INR in patients taking warfarin. However, from their small sample of 92 consenting patients, at least 11 died of cancer in a follow-up period of only 3 months. Presumably, therefore, more than one in eight of the sample had been diagnosed with cancer before or during the study.The investigators conclude that the case for the use of low-dose oral vitamin K is compelling, with no increase in the risk of thrombosis or warfarin resistance. However, many patients with thrombosis secondary to cancer (Trousseau's syndrome) are already resistant to warfarin. Some argue also that low-molecular-weight heparin should replace warfarin treatment at diagnosis of Trousseau's syndrome.2Walsh-McMonagle D Green D Low-molecular- weight heparin in the management of Trousseau's syndrome.Cancer. 1997; 80: 649-655Crossref PubMed Scopus (71) Google Scholar The large increase in risk for developing many cancers after venous thromboembolism3Baron JA Gridley G Weiderpass E Nyren O Kinet M Venous thromboembolism and cancer.Lancet. 1998; 351: 1077-1080Summary Full Text Full Text PDF PubMed Scopus (462) Google Scholar means that precise indications for warfarin use are essential data, but Crowther and colleagues do not provide these details.Therapeutic INRs are more difficult to sustain in cancer patients than in non-cancer patients.4Bona RD Sivjee KY Hickey AD Wallace DM Wajcs SB The efficacy and safety of oral anticoagulation in patients with cancer.Thromb Haemost. 1995; 74: 1055-1058PubMed Google Scholar Distinct tumour types activate the coagulation system differently; for example, patients with colorectal cancer require a lower mean daily warfarin dose to achieve a given range of INR than patients with other cancers.5Forman WB Cook CE Zacharski LR et al.Influence of age, performance status, body weight, and tumor type in individuals with cancer on the disposition of warfarin and its enantiomers: Department of Veterans Affairs cooperative study number 75.J Lab Clin Med. 1992; 119: 280-284PubMed Google Scholar Perhaps each patient's indication for warfarin dose should be reviewed when deciding whether to simply administer vitamin K if a patient's INR becomes raised, since changes in coagulation might be a sign that a cancer has developed. M Crowther and colleagues1Crowther MA Julian J McCarty D et al.Treatment of warfarin-associated coagulopathy with oral vitamin K: a randomised controlled trial.Lancet. 2000; 356: 1551-1553Summary Full Text Full Text PDF PubMed Scopus (164) Google Scholar show that vitamin K lowers the INR in patients taking warfarin. However, from their small sample of 92 consenting patients, at least 11 died of cancer in a follow-up period of only 3 months. Presumably, therefore, more than one in eight of the sample had been diagnosed with cancer before or during the study. The investigators conclude that the case for the use of low-dose oral vitamin K is compelling, with no increase in the risk of thrombosis or warfarin resistance. However, many patients with thrombosis secondary to cancer (Trousseau's syndrome) are already resistant to warfarin. Some argue also that low-molecular-weight heparin should replace warfarin treatment at diagnosis of Trousseau's syndrome.2Walsh-McMonagle D Green D Low-molecular- weight heparin in the management of Trousseau's syndrome.Cancer. 1997; 80: 649-655Crossref PubMed Scopus (71) Google Scholar The large increase in risk for developing many cancers after venous thromboembolism3Baron JA Gridley G Weiderpass E Nyren O Kinet M Venous thromboembolism and cancer.Lancet. 1998; 351: 1077-1080Summary Full Text Full Text PDF PubMed Scopus (462) Google Scholar means that precise indications for warfarin use are essential data, but Crowther and colleagues do not provide these details. Therapeutic INRs are more difficult to sustain in cancer patients than in non-cancer patients.4Bona RD Sivjee KY Hickey AD Wallace DM Wajcs SB The efficacy and safety of oral anticoagulation in patients with cancer.Thromb Haemost. 1995; 74: 1055-1058PubMed Google Scholar Distinct tumour types activate the coagulation system differently; for example, patients with colorectal cancer require a lower mean daily warfarin dose to achieve a given range of INR than patients with other cancers.5Forman WB Cook CE Zacharski LR et al.Influence of age, performance status, body weight, and tumor type in individuals with cancer on the disposition of warfarin and its enantiomers: Department of Veterans Affairs cooperative study number 75.J Lab Clin Med. 1992; 119: 280-284PubMed Google Scholar Perhaps each patient's indication for warfarin dose should be reviewed when deciding whether to simply administer vitamin K if a patient's INR becomes raised, since changes in coagulation might be a sign that a cancer has developed. 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