Vitamin K Deficiency

Key Features

• May occur as a result of

  • Deficient dietary intake (eg, green leafy vegetables and soybeans)

  • Malabsorption

  • Decreased production by intestinal bacteria (due to treatment with chemotherapy or antibiotics)

• Vitamin K is required for normal function of vitamin K epoxide reductase that assists in posttranslational gamma-carboxylation of the coagulation factors II, VII, IX, and X, which is necessary for their activity

• Risk of developing vitamin K deficiency is high in hospitalized patients taking broad-spectrum antibiotics who have poor or no oral intake

Clinical Findings

• Mild to moderate deficiency typically features a prolonged prothrombin time (PT)

• Severe deficiency: prolonged activated partial thromboplastin time (aPTT)

• Low levels of individual clotting factors II, VII, IX, and X

Diagnosis

• Concomitant low factor V activity level not indicative of isolated vitamin K deficiency but may indicate an underlying defect in liver synthetic function

Treatment

• Vitamin K₁ (phytonadione) may be administered via intravenous or oral routes

• Intravenous administration (1 mg/day) results in faster normalization of a prolonged PT than oral administration (5–10 mg/day)

• Parenteral doses should be given at lower doses and slowly (eg, over 30 minutes) with concomitant monitoring to avoid possible anaphylaxis

• Oral absorption is typically excellent; partial improvement in PT should be seen within 18–24 hours

• Subcutaneous route not recommended due to erratic absorption