Vitamin K : Dosing and Safety

by MedlinePlus

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Dosing

Dietary intake

Foods rich in vitamin K: Green, leafy vegetables such as spinach, broccoli, asparagus, watercress, cabbage, cauliflower, green peas, beans, olives, canola, soybeans, meat, cereals, and dairy products. Cooking does not remove significant amounts of vitamin K from these foods.

Adults (18 years and older)

Vitamin K deficiency: Management should be under medical supervision. If the PT is only slightly elevated and poor dietary intake is thought to be the cause, increasing the ingestion of vitamin K-rich foods can be tried. In non-emergency situations, oral vitamin K1 (Phytonadione, AquaMEPHYTON, Mephyton, Konakion) can be given in a daily dose of 5-10mg (single doses up to 25mg are given in some cases). If there is a concern of bile salt deficiency or malabsorption in the ileum, a water-soluble oral form of vitamin K can be considered. If necessary, vitamin K1 can be injected at a dose of 10mg, repeated after 8-12 hours, or administered daily until the deficiency is corrected.

Elevated PT/INR (warfarin reversal): Management should be under medical supervision. Generally, if the INR is higher than intended but less than 6, and the patient is not bleeding, then warfarin can be held for 2-3 days then restarted when the range is acceptable. If the INR is 6-10 without bleeding, then 1-2mg of vitamin K1 (Phytonadione, AquaMEPHYTON) can be given subcutaneously. If the INR is greater than 10 without bleeding, then 3mg of vitamin K1 can be administered subcutaneously. In cases of serious bleeding or very high INR (greater than 20), 10mg of vitamin K1 can be given subcutaneously with fresh frozen plasma or prothrombin complex concentrate. If oral administration is preferred, doses between 50-200mg have been given. During treatment, blood tests for PT/INR should be followed to check for normalization. If the PT/INR does not correct, a physician should consider causes such as severe liver disease or disseminated intravascular coagulation (DIC). In urgent situations, a dilution of vitamin K can be given intravenously, although there is a risk of serious allergic (anaphylactoid) reactions. In cases of life-threatening bleeding, hospitalization and treatment with fresh frozen plasma (FFP) may be necessary.

Pre-procedure (warfarin reversal): Management should be under medical supervision. In general, for minor procedures such as tooth extractions, some eye operations, or biopsies, reversal may not be necessary if the INR is 2.5 or lower. For more serious procedures, the approach depends on the initial reason for anticoagulation. For patients taking warfarin for prosthetic heart valves, the warfarin can be held for four days prior to surgery while the patient is given low-molecular-weight heparin for up to 12 hours before the procedure. Warfarin can be restarted after surgery. For patients with atrial fibrillation or cardiomyopathy, warfarin can be held for four days prior to surgery, and then restarted afterwards. In high-risk patients with a history of deep venous thrombosis (DVT) or a pulmonary embolus (PE), after warfarin is held, intravenous unfractionated heparin coverage can be given until six hours before surgery, then restarted 12 hours after surgery. Warfarin can then be restarted. More aggressive measures may be necessary in patients with recent or multiple past blood clots. In patients with a history of an arterial clot, warfarin can be held for four days, and the INR can be checked on the day before surgery. If the INR is greater than 1.7, then 1mg of vitamin K can be given subcutaneously. On the day of surgery, if the INR is still elevated, fresh frozen plasma should be administered.

Acute liver dysfunction: A minority of patients with severe acute liver dysfunction has subclinical vitamin K deficiency at the time of presentation, which is corrected by a single dose of intravenous K1. The intestinal absorption of mixed-micellar K1 has been shown to be unreliable in adults with severe acute liver dysfunction.

Children (younger than 18 years)

Recommended dose at birth: Vitamin K1 given by injection has been shown in newborns and young infants to prevent "hemorrhagic disease of newborn," also known as vitamin K deficiency bleeding (VKDB). The American Academy of Pediatrics therefore recommends administering a single intramuscular injection of 0.5 to 1mg of vitamin K1 to all newborns. Oral dosing is generally not regarded as adequate for prevention, particularly in breastfeeding infants.

Warfarin toxicity/reversal: Should be under strict medical supervision. Initial doses of 1-5mg of vitamin K1 (Phytonadione, AquaMEPHYTON) have been used, with daily increases based on PT/INR values.

Note: Menadiol (not available in the U.S.) should not be given to infants or children due to rare reports of liver damage and blood cell toxicity (hemolytic anemia).

Safety

Allergies

Intravenous or intramuscular vitamin K has been associated rarely with anaphylactoid reactions, including shock, heart attack, respiratory arrest, and death. Therefore, these routes of administration should be avoided if possible. If given intravenously, preparations should be dilute and administration should be slow, under strict medical supervision.

Skin hypersensitivity reactions are rare, and may occur in particular with injections of vitamin K1 (Phytonadione, AquaMEPHYTON). A raised, itchy plaque may arise at the injection site which may take 1-2 months to resolve, and can cause a scar.

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