Question

A newborn weighing 850 g requires the birth dose of menadione. What is the correct dose?

• A. 0.3 mg
• B. 0.5 mg
• C. 1 mg
• D. 2 mg

Hint:

Vitamin K at Birth Dosing:
$\bullet$ Weight $\ge 1000\text{ g}$: $1\text{ mg}$ IM
$\bullet$ Weight $<1000\text{ g}$: $0.3\text{ mg}$ (or $0.5\text{ mg}$) IM.

Answer 1

The Correct Option is A

Concept:
Vitamin K prophylaxis is administered to all newborns at birth to prevent Vitamin K Deficiency Bleeding (VKDB), formerly known as Hemorrhagic Disease of the Newborn.
Dosing is weight-stratified to achieve adequate hemostasis while avoiding unnecessary tissue toxicity or overdosing in extremely low birth weight (ELBW) infants.
Explanation:
• Vitamin K deficiency bleeding can occur early (first 24 hours), classically (days 2--7), or late (weeks 2--24, presenting with intracranial hemorrhage).

• Standard guidelines (AAP, ESPGHAN, and WHO) recommend weight-adjusted intramuscular administration of vitamin K1 (phytomenadione/phytonadione) at birth:
1. Birth weight $>1000\text{ g$ (or term neonates):} $1.0\text{ mg}$ intramuscularly.
2. Preterm infants weighing $<1000\text{ g$ (ELBW):} Reduced dose of $0.3\text{ mg$ to $0.5\text{ mg}$} (specifically $0.3\text{ mg/kg}$ or a fixed dose of $0.3\text{ mg}$) intramuscularly.

• An infant weighing $850\text{ g}$ falls into the extremely low birth weight category ($<1000\text{ g}$), where a single IM dose of $0.3\text{ mg}$ provides optimal plasma vitamin K levels without overloading hepatic metabolic pathways.
Final Answer:
For an ELBW preterm infant weighing 850 g ($<1000\text{ g}$), the recommended birth dose of vitamin K is 0.3 mg IM.