Indications of Vitamin K

1. Vitamin K Deficiency States (Primary Indication)

a. Inadequate Intake

• Rare in adults on normal diets since vitamin K is present in many foods (leafy greens, egg yolk, liver) and is also synthesized by intestinal bacteria.
• Can occur in patients on prolonged intravenous (parenteral) nutrition - these patients should receive 1 mg phytonadione per week as prophylaxis.
• Broad-spectrum antibiotic use can suppress gut flora, reducing endogenous synthesis. Certain cephalosporins (e.g., cefamandole) inhibit vitamin K oxidoreductase (VKOR) by a warfarin-like mechanism, causing hypoprothrombinemia - supplementation with vitamin K is required alongside such antibiotics.

b. Inadequate Absorption (Malabsorption)

• Vitamin K is a fat-soluble vitamin that requires bile salts and pancreatic juice for absorption (10-80% of ingested vitamin K is absorbed).
• Indications include:
  • Biliary obstruction (intrahepatic or extrahepatic) - lack of bile prevents vitamin K absorption, depleting vitamin K-dependent clotting factors (II, VII, IX, X) over weeks
  • Fat malabsorption syndromes (celiac disease, short bowel syndrome, inflammatory bowel disease)
  • Prolonged diarrhea or steatorrhea

c. Debilitated/Geriatric Patients with Marginal Nutrition

• Reduced gut flora + marginal dietary intake can lead to hypoprothrombinemia requiring supplementation.

2. Hemorrhagic Disease of the Newborn (Neonatal Prophylaxis)

• Newborns have sterile intestines at birth, lacking bacteria that synthesize vitamin K.
• Human breast milk provides only about one-fifth of the daily requirement for vitamin K; formula is supplemented.
• Decreased plasma concentrations of vitamin K-dependent clotting factors at birth can cause hemorrhagic disease of the newborn (HDN), also called Vitamin K Deficiency Bleeding (VKDB).
• Routine prophylaxis: A single intramuscular dose of 1 mg phytonadione at birth is required by law in the United States. This raises clotting factor levels and controls bleeding within ~6 hours.
• The dose may need to be increased or repeated if the mother received warfarin or anticonvulsant therapy.
• Alternatively, mothers on anticonvulsants may receive oral vitamin K (20 mg/day for 2 weeks) prior to delivery.

3. Reversal of Warfarin / Vitamin K Antagonist Overdose

• Warfarin inhibits vitamin K activity, depleting vitamin K-dependent clotting factors II, VII, IX, and X (and proteins C and S), producing a coagulopathy.
• Vitamin K (phytonadione) is the logical reversal agent for warfarin toxicity.
• Important limitation: Reversal by vitamin K requires 12-24 hours for effectiveness. It is therefore NOT recommended as sole therapy for life-threatening hemorrhage, for which prothrombin complex concentrates (PCC) or fresh frozen plasma (FFP) are preferred for immediate reversal.
• Preferred route is oral when feasible. For urgent reversal, slow IV infusion can be used - rapid IV administration risks severe anaphylactoid reactions (rate ~0.03% with current preparations).
• Subcutaneous route is relatively ineffective and should be avoided in coagulopathic patients.

4. Liver Disease with Impaired Clotting Factor Synthesis

• Prolonged jaundice in liver disease causes malabsorption of fat-soluble vitamins including vitamin K.
• An elevated prothrombin time (PT) may indicate either vitamin K deficiency due to malabsorption or significant hepatocellular dysfunction.
• If PT corrects with vitamin K administration, the cause is deficiency; failure to correct suggests intrinsic hepatocellular damage (the liver cannot synthesize clotting factors regardless of vitamin K availability).

5. Bone Health (Emerging Indication)

• Vitamin K deficiency can affect bone health, as vitamin K-dependent proteins (e.g., osteocalcin) are involved in bone mineralization.
• This is mentioned as a secondary indication in the context of deficiency states.

Route of Administration Summary

• Goodman & Gilman's The Pharmacological Basis of Therapeutics, Therapeutic Uses section
• Lippincott Illustrated Reviews: Biochemistry, 8th ed., Clinical Indications for Vitamin K
• Tintinalli's Emergency Medicine: A Comprehensive Study
• Harrison's Principles of Internal Medicine 22E
• Goldman-Cecil Medicine