NCLEX Review Guide: Phytonadione (Vitamin K)

Mechanism of Action

• Phytonadione (Vitamin K1) is essential for the synthesis of clotting factors II, VII, IX, and X in the liver
• Acts as a cofactor for the enzyme that converts precursor proteins into active clotting factors
• Reverses anticoagulant effects of warfarin by promoting normal blood clotting

Newborn Administration

• Prophylactic dose: 0.5-1 mg IM within 1 hour of birth to prevent hemorrhagic disease of the newborn
• Given in vastus lateralis muscle using 25-gauge needle
• Newborns have sterile gut at birth, lacking vitamin K-producing bacteria

1. Verify physician order and newborn identity
2. Draw up 0.5-1 mg in tuberculin syringe
3. Clean injection site (vastus lateralis)
4. Insert needle at 90-degree angle
5. Inject slowly and withdraw needle
6. Apply gentle pressure, document administration

Antepartum Use

• May be given to mothers on anticoagulant therapy before delivery
• Hemorrhagic disease prevention when maternal bleeding disorders are present
• Monitor for maternal allergic reactions, especially with IV administration

Assessment & Monitoring

• Monitor PT/INR levels when reversing warfarin effects
• Assess for signs of bleeding: petechiae, bruising, prolonged bleeding from injection sites
• Watch for anaphylaxis with IV administration - have emergency equipment ready

• ☐ I can explain why newborns need vitamin K prophylaxis
• ☐ I know the correct IM injection site for newborns
• ☐ I understand the timing requirements for administration
• ☐ I can identify signs of vitamin K deficiency
• ☐ I know the difference between vitamin K forms
• ☐ I understand proper IV administration techniques