Vitamin K in neonates: how to administer, when and to whom.

Vitamin K-dependent factors are lower in neonates than in adults, and these anomalies are more prevalent in preterm neonates and in breast-fed infants. Vitamin K deficiency can account for vitamin K deficiency bleeding (VKDB) which occurs in 3 forms--early, classic and late. Vitamin K should be administered to all neonates at birth or immediately afterwards. However, the protocols for administration (route of administration, dosage, number of doses) remain a subject of discussion. Oral administration of a single dose of vitamin K protects against classical and early VKDB, but is less effective than intramuscular (IM) prophylaxis for the prevention of late VKDB. Although an increased risk of solid tumour, associated vitamin K administration, can be definitively excluded, a low potential risk of lymphoblastic leukaemia in childhood can not be ruled out. For formula-fed neonates without risk of haemorrhage, a 2 mg oral dose of vitamin K at birth, followed by a second 2 mg oral dose between day 2 and 7, is probably sufficient to prevent VKDB. For infants who are exclusively or nearly exclusively breast-fed, weekly oral administration of 2mg (or 25 microg/day) vitamin K after the initial 2 oral doses is justified at completion of breast-feeding. For neonates at high risk of haemorrhage (premature, neonatal disease, birth asphyxia, difficult delivery, any illness which will delay feeding, known hepatic disease, maternal drugs inhibiting vitamin K activity), the first dose must be administered by the IM or slow intravenous route. Doses should be repeated, particularly in premature infants, by a route of administration decided for each dose according to the clinical state of the infant. For infants of mothers treated with drugs inhibiting vitamin K activity, antenatal maternal prophylaxis (10 to 20 mg/day orally for 15 to 30 days before delivery) prevents early VKDB. After neonatal prophylaxis, as for infants at high risk of haemorrhage, doses need to be repeated at a rate and route of administration decided for each dose, according to the clotting factor profile specific for each infant.