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  1. Pharmacology. Vitamin K1 is an essential cofactor in the hepatic synthesis of coagulation factors II, VII, IX, and X. In adequate doses, vitamin K1 reverses the inhibitory effects of coumarin and indanedione derivatives on the synthesis of these factors. Note: Vitamin K3 (menadione) is not effective in reversing excessive anticoagulation caused by these agents. After parenteral vitamin K1 administration, there is a 6- to 8-hour delay before vitamin K–dependent coagulation factors begin to achieve significant levels, and peak effects are not seen until 1–2 days after the initiation of therapy. The duration of effect is 5–10 days. The response to vitamin K1 is variable, and the optimal dosage regimen is unknown; it is influenced by the potency and amount of the ingested anticoagulant, vitamin K pharmacokinetics, and the patient's hepatic biosynthetic capability. Fresh frozen plasma or whole blood is indicated for immediate control of serious hemorrhage.

  2. Indications

    1. Excessive anticoagulation caused by coumarin and indanedione derivatives, as evidenced by an elevated prothrombin time. Vitamin K1 is not indicated for empiric treatment of anticoagulant ingestion, as most cases do not require treatment, and its use will delay the onset of an elevated prothrombin time as a marker of a toxic ingestion.

    2. Vitamin K deficiency (eg, malnutrition, malabsorption, or hemorrhagic disease of the newborn) with coagulopathy.

    3. Hypoprothrombinemia resulting from salicylate intoxication.

  3. Contraindications. Do not use in patients with known hypersensitivity to vitamin K or preservatives.

  4. Adverse effects

    1. Black box warning. Anaphylactoid reactions have been reported after intravenous administration and have been associated with fatalities. Intravenous use should be restricted to true emergencies; the patient must be monitored closely in an intensive care setting. Severe reactions and fatalities have also been associated with intramuscular administration and resembled hypersensitivity reactions.

    2. Intramuscular administration in patients receiving anticoagulants may cause large, painful hematomas. This can be avoided by using the oral or subcutaneous route.

    3. Patients receiving anticoagulants for medical reasons (eg, deep vein thrombosis or prosthetic heart valves) may experience untoward effects from complete reversal of their anticoagulation status. Preferably, such patients should receive small quantities of fresh frozen plasma or extremely small titrated doses (0.5–1 mg) of vitamin K until the prothrombin time is in the desired therapeutic range (eg, 1.5–2 times normal). Adjunctive anticoagulation with heparin may be required until the desired prothrombin time is achieved.

    4. Use in pregnancy. FDA Category C (indeterminate). Vitamin K1 crosses the placenta readily. However, this does not preclude its acute, short-term use in a seriously symptomatic patient (See Introduction in Section III).

  5. Drug or laboratory interactions. Empiric use after an acute anticoagulant overdose will delay (for up to several days) the onset of elevation of the prothrombin time, and this may give a false impression of insignificant ingestion in a case of serious “superwarfarin” overdose (See Warfarin and Related Rodenticides).

  6. Dosage and method of administration

    1. Oral. The usual dose of vitamin K1 (not menadione or vitamin K3) is 10–50 mg 2–4 times a day ...

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