フィトナジオン (ビタミンK1)

使用用途

• Adjunctive therapy of acute liver failure
• Anticoagulant rodenticide toxicity (exposed but non-bleeding)
• Anticoagulant rodenticide toxicity (bleeding patient)
• Anticoagulant rodenticide toxicity (symptomatic)
• Known 1st generation coumarin toxicity or vitamin K1 deficiency
• Known 2nd generation coumarin (brodifacoum) toxicity
• Known inandione (diphacinone) or unknown anticoagulant toxicity
• Liver disease (pre-biopsy)
• Warfarin (or related compounds) toxicity
• Warfarin (or related compounds) toxicity
• Warfarin (or related compounds) toxicity
• Warfarin (or related compounds) toxicity

投与方法

考えられる副作用

• Anaphylactoid reactions (especially following IV administration)
• Acute bleeding from the injection site (IM administration during early stages of treatment)
• Slow or poor absorption from SC or PO routes in hypovolemic patients
• Anaphylactic reactions (following IV administration)
• Haemolytic anaemia (in cats when overdosed)
• Anaphylaxis (primarily with IV administration)
• Injection site reactions (pain, swelling)
• Hematoma formation at injection sites (due to underlying coagulopathy)

注意事項と禁忌

• Known hypersensitivity to phytonadione or its components
• Hypoprothrombinemia due to hepatocellular damage (Vitamin K cannot correct this if the liver cannot synthesize the protein precursors)
• Intravenous administration (relative contraindication due to anaphylaxis risk)
• Known hypersensitivity to phytomenadione
• Intramuscular administration in severely coagulopathic patients (risk of severe hematoma)
• **Intravenous Administration Warning:** The FDA-CVM warns against administering phytonadione IV due to a significant risk of severe anaphylactoid reactions. If IV use is absolutely necessary (e.g., severe bleeding with very high INR in large animals), it must be diluted and given extremely slowly. **Injection Site Bleeding:** IM injections can cause acute bleeding at the site in coagulopathic patients. Use small-gauge needles for SC or IM injections. **Delayed Onset:** It takes 6-12 hours for new clotting factors to be synthesized. Emergency needs for clotting factors in actively bleeding patients MUST be met with blood products (fresh frozen plasma or whole blood). **Absorption:** SC or PO doses may be poorly absorbed in hypovolemic animals. Oral absorption requires bile salts and is significantly enhanced (4-5x) by administering with a fatty meal.

薬物相互作用

• Oral Antibiotics: May decrease the numbers of Vitamin K-producing bacteria in the gut, though chronic therapy usually has no significant effect on phytonadione absorption.
• Mineral Oil: Concomitant oral administration may reduce the GI absorption of oral Vitamin K.
• Warfarin (and other coumarin/indanedione anticoagulants): Phytonadione directly antagonizes the anticoagulant effects of these drugs.
• Phenylbutazone, Aspirin, Chloramphenicol, Sulfonamides, Diazoxide, Allopurinol, Cimetidine, Metronidazole, Anabolic Steroids, Erythromycin, Ketoconazole, Propranolol, Thyroid Drugs: May prolong or enhance the effects of anticoagulants, thereby antagonizing some of the therapeutic effects of phytonadione.
• Aspirin: Antagonizes the effects of vitamin K
• Chloramphenicol: Antagonizes the effects of vitamin K
• Allopurinol: Antagonizes the effects of vitamin K
• Diazoxide: Antagonizes the effects of vitamin K
• Cimetidine: Antagonizes the effects of vitamin K
• Metronidazole: Antagonizes the effects of vitamin K

よくある質問