What is the recommended vitamin K1 (phytonadione) prophylaxis dose, route, and timing for newborns, and what oral regimen should be used if intramuscular injection is not possible?

Vitamin K Prophylaxis for Newborns

All newborns should receive 0.5 to 1.0 mg of vitamin K1 (phytonadione) intramuscularly within one hour of birth—this is the gold standard for preventing all forms of vitamin K deficiency bleeding (VKDB). 1, 2

Intramuscular Administration (Preferred Route)

The intramuscular route is superior because it reliably prevents early, classic, and late VKDB with a single dose. 2, 3

• Dose: 0.5 to 1.0 mg vitamin K1 intramuscularly 1, 2
• Timing: Within one hour of birth 2
• Documentation: Record the date, dose, and route of administration in the medical record 3
• The dose may be delayed until after the first breastfeeding if desired, but should not be postponed beyond one hour 1

Oral Administration (Alternative if IM Refused)

If parents refuse intramuscular administration after adequate counseling, oral vitamin K can be offered, but you must emphasize that oral regimens are less effective than IM and require strict adherence to multiple doses. 2, 3

Oral Regimen Options:

Option 1 (Three-dose regimen):

• 2 mg at birth
• 2 mg at 4-6 days
• 2 mg at 4-6 weeks 2, 3

Option 2 (Weekly regimen for 3 months):

• 2 mg at birth
• Then 1 mg weekly for 12 weeks (3 months total) 2, 3

Critical caveat: If the infant vomits or regurgitates within one hour of oral administration, repeat the dose 3. Document parental refusal of IM administration because of the increased risk of late VKDB with oral regimens 3.

Contraindications to Oral Route

The oral route is NOT appropriate for: 3, 4

• Preterm infants
• Infants with cholestasis or impaired intestinal absorption
• Infants too unwell to take oral medication
• Infants whose mothers took medications interfering with vitamin K metabolism (anticonvulsants, anticoagulants, antituberculosis drugs)
• Any infant at high risk of hemorrhage (birth asphyxia, difficult delivery, neonatal disease)

For these high-risk infants, give 1 mg IM or slow IV immediately after birth. 4

Special Populations

Preterm Infants on Parenteral Nutrition:

• Require 10 μg/kg/day of vitamin K1 in their parenteral nutrition solution 1, 2, 5

Infants of Mothers on Vitamin K-Inhibiting Drugs:

• Give 1 mg IM as soon as possible after birth 6, 4
• Consider antenatal maternal prophylaxis (10-20 mg/day orally for 15-30 days before delivery) to prevent early VKDB 4

Why This Matters: The Clinical Context

Newborns have physiologically low vitamin K-dependent coagulation factors (II, VII, IX, X), and breast milk contains inadequate vitamin K concentrations, making exclusively breastfed infants particularly vulnerable 5, 6. Without prophylaxis, VKDB can cause catastrophic intracranial hemorrhage with permanent neurological damage or death. Single-dose IM vitamin K at birth reduces this risk to nearly zero. 3, 7

Safety Profile

Vitamin K1 (phylloquinone) has no known toxicity or adverse effects at prophylactic doses 2, 5. The previously reported association between IM vitamin K and childhood cancer has been definitively refuted by subsequent large studies 7.

Monitoring

• Routine monitoring of vitamin K levels is not recommended for healthy term infants 5
• For at-risk infants, PIVKA-II (undercarboxylated vitamin K-dependent proteins) is the most sensitive biomarker when available 2, 5
• A prompt shortening of prothrombin time within 2-4 hours after vitamin K administration confirms VKDB as the diagnosis 5

Common Pitfalls to Avoid

• Do not use oral vitamin K3 (menadione)—only vitamin K1 (phylloquinone) is acceptable 8
• Do not assume a single oral dose at birth is sufficient—oral prophylaxis requires multiple doses to prevent late VKDB 3, 6
• Do not give oral vitamin K to preterm or sick infants—they require parenteral administration 3, 4
• Do not forget to document parental refusal if IM is declined, as this has medicolegal implications given the preventable nature of late VKDB 3