When calculating medication dosage for a child, what is the most crucial metric?

In pediatric medication dosing, weight is the most crucial metric because children's body compositions and metabolic rates vary significantly depending on their weight. Medication dosages are typically calculated as a function of the child's weight, commonly expressed as milligrams per kilogram. This method helps ensure that children receive an appropriate amount of medication that accounts for their size and physiology.

Using weight allows for more accurate dosing compared to age, height, or gender, which may not consistently reflect the child's capacity to metabolize the drug. For example, two children of the same age can have drastically different weights and therefore may require different dosages of the same medication. Hence, basing the calculation on weight promotes both efficacy and safety in pharmacotherapy for children.