Final answer:
Drug dosages for a child, the factor used is Body surface area (BSA) (option b). BSA is preferred for children because it accurately reflects the metabolic mass and how drugs are metabolized and eliminated as children grow and develop.
Step-by-step explanation:
The factor used to calculate drug dosages for a child is Body surface area (BSA). When determining dosages for pediatric patients, healthcare providers often use BSA as it provides a more accurate assessment of the metabolic mass of the child compared to simple weight- or age-based calculations. BSA takes into account the child's total body size, which affects how the drug is distributed and eliminated from the body. This is critical since pediatric patients are still in developmental stages and their bodies process drugs differently than adults do.
In adults and children aged 12 and older, typically a single standard dose is used. However, for children, the dosage is often based on their BSA because their bodies metabolize drugs differently due to their growth and development. Other factors such as age, gender, genetic characteristics, and even food can influence drug pharmacokinetics, which includes how drugs are absorbed, distributed, metabolized, and excreted by the body.