By which route should phytonadione be administered to a newborn?

Phytonadione, also known as vitamin K, is typically administered to newborns via the intramuscular route. This method is preferred because it allows for rapid absorption and a sustained effect of the medication, which is essential for newborns who are at risk for vitamin K deficiency and potential bleeding issues, such as hemorrhagic disease of the newborn.

Administering phytonadione intramuscularly ensures that it can be delivered effectively into the muscle tissue, where it can be absorbed into the bloodstream efficiently. This is particularly important for newborns since their gastrointestinal systems are not fully developed, making oral administration less reliable for the absorption of vitamin K at this stage. The intramuscular route also allows for a more accurate and controlled dosage, which is vital in a neonatal population.

Other administration routes, such as intravenous, subcutaneous, or oral, may not provide the same level of efficacy or may pose difficulties and risks. For example, intravenous administration requires additional technical skills and equipment, while subcutaneous administration may not achieve the desired pharmacokinetics in this age group. Oral administration can also be problematic due to the variable absorption in newborns, making it less suitable for the immediate prevention of vitamin K deficiency.