Final answer:
Infants have a quicker drug induction mainly due to their increased metabolic rate and blood volume, as well as faster minute respiration rates, which all contribute to how drugs are processed in the body.
Step-by-step explanation:
The factors that speed induction in infants relative to adults include increased metabolic rate and increased blood volume. Infants have a higher basal metabolic rate compared to adults. This elevated metabolic rate implies that drugs will circulate through an infant's body faster, leading to a quicker induction time when anesthesia is administered. Moreover, proportionally, infants have increased minute respiration, and their circulatory adjustments after birth, such as closure of fetal shunts, contribute to the differences in drug distribution and metabolism compared to adults.
Gastrointestinal and urinary adjustments also play a role in how infants process substances differently than adults. For instance, a newborn's gastrointestinal tract is sterile at birth and the first consumption of breast milk introduces beneficial bacteria that aid in digestion. Thus, the presence of an immature gut flora might influence the absorption and effect of oral medications. Additionally, newborns have a unique thermoregulatory method involving the breakdown of brown fat, rather than shivering, which is an important heat regulator and can influence metabolism.