Interaction of Antibiotics With Vitamin K

To the Editor.— In our experience, and that of others,1acute vitamin K deficiency is a common occurrence in patients who are on no oral intake and receiving antibiotics, as is likely to occur in patients in intensive care units. This deficiency may appear in a period as brief as 48 hours after admission if the patient was nutritionally impaired. This occurrence manifests mainly in a prolongation of the prothrombin time, and it can lead to serious bleeding. Since we instituted routine replacement with parenteral vitamin K, this picture has become a rarity. Those patients still having prolonged prothrombin times were studied in detail (assaying their clotting factors II, V, VII/X, and VIII). As expected, it was found that those patients who failed to respond to intravenous vitamin K had underlying liver disease, and, accordingly, their factor V was decreased (not a vitamin K-dependent factor also synthesized by the