When giving a highly protein-bound medication to an infant, what happens to the availability of free medication?

When administering a highly protein-bound medication to an infant, less free medication is available due to the properties of protein binding. Medications that are highly protein-bound primarily attach to plasma proteins, such as albumin. In infants, particularly those who may have lower levels of plasma proteins or altered binding capacity, a larger proportion of the drug may remain bound to these proteins, which decreases the amount of free or unbound medication in circulation.

Since only free medication can exert therapeutic effects or be metabolized and eliminated, a reduction in the free fraction means there is less active drug available to interact with its target sites in the body. This concept is particularly critical in pediatric populations, where protein levels and binding affinities can differ significantly from adults. Understanding the impact of protein binding helps ensure that dosages are appropriately adjusted for infants to achieve the desired therapeutic effects without causing toxicity.