The most important organ for drug elimination in the newborn is the:

• A. GI Tract
• B. Lungs
• C. Kidney
• D. Liver

Answer: (C)

Renal excretion is the primary route by which drugs are eliminated in a newborn. The kidneys are the main organ responsible for clearing many medications, especially those that are water-soluble and excreted unchanged. In newborns, renal function is immature at birth, with low glomerular filtration and limited tubular excretion, but it undergoes rapid maturation after birth. Because of this, the rate at which drugs are cleared largely depends on how developed the infant’s kidneys are, making renal clearance the dominant determinant of drug elimination in the neonatal period. The liver also metabolizes drugs, and some drugs are excreted via bile or through the lungs, but for most drugs used in neonates, the kidneys play the central role in elimination.