When infants have decreased serum protein levels, they are at greater risk for:

• A. Adverse reactions
• B. Drug toxicity
• C. Non-therapeutic drug levels
• D. Allergic reactions

Answer: (B)

Lower serum protein levels in infants reduce binding of drugs to proteins like albumin. Many medications are highly protein-bound, so only the unbound portion is active and able to exert effects or be cleared. When binding is decreased, the free drug concentration rises, increasing pharmacologic activity and the risk of toxicity, especially for drugs with a narrow therapeutic window. Allergic reactions are immune-mediated and not directly caused by low protein binding, and subtherapeutic levels come from factors other than reduced protein binding.