Influence of body weight on response to subcutaneous vitamin K administration in over-anticoagulated patients.
OBJECTIVE
To determine the influence of body weight on the international normalized ratio (INR) response to a fixed dose of vitamin K in overanticoagulated patients.


METHODS
Retrospective review of records of patients who received 1 mg of vitamin K subcutaneously to correct excessive INR. Dose of vitamin K in milligrams per kilograms plotted against change in INR in 24 hours.


RESULTS
Fifteen patients were identified who met all inclusion criteria. Linear regression analysis plotted INR response at 24 hours versus dose of vitamin K adjusted for body weight. Pearson's product moment correlation (R = 0.85) indicated a significant relationship between INR response at 24 hours to an adjusted body weight dose of subcutaneous vitamin K (P = 0.0000523). A strong correlation (r = 0.69) also existed between INR response at 24 hours and the actual body weight dose of subcutaneous vitamin K (P = 0.004).


CONCLUSIONS
In overanticoagulated patients, variability in response to vitamin K may be explained by variability in body weight. Dosing vitamin K according to body weight may result in a more predictable INR response.
Kelly
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KC
Veterans Affairs North Texas Health Care System, Dallas, Texas 75216, USA. Kevin.Kelly@med.va.gov
Raj
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Weideman
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RA
D001777:Blood Coagulation / Q000187:drug effects*; D001835:Body Weight; D006801:Humans; D007279:Injections, Subcutaneous; D019934:International Normalized Ratio; D016014:Linear Models; D012189:Retrospective Studies; D014812:Vitamin K / Q000008:administration & dosage*
D014812:Vitamin K