Pediatrics (also spelled paediatrics or pædiatrics) is the branch of medicine that involves the medical care of infants, children, and adolescents. People must be under pediatric care up to the age of 21, though usually only minors under 18 are required to be under pediatric care. A medical doctor who specializes in this area is known as a pediatrician, or paediatrician.
The word pediatrics and its cognates mean "healer of children"; they derive from two Greek words: παῖς (pais "child") and ἰατρός (iatros "doctor, healer").
Pediatricians work both in hospitals, particularly those working in its subspecialties such as neonatology, and as outpatient primary care physicians.
Many drug absorption differences between pediatric and adult populations revolve around the stomach. Neonates and young infants have increased stomach pH due to decreased acid secretion, thereby creating a more basic environment for drugs that are taken by mouth. Acid is essential to degrading certain oral drugs before systemic absorption. Therefore, the absorption of these drugs in children is greater than in adults due to decreased breakdown and increased preservation in a less acidic gastric space.
Children also have an extended rate of gastric emptying, which slows the rate of drug absorption.
Drug absorption also depends on specific enzymes that come in contact with the oral drug as it travels through the body. Supply of these enzymes increase as children continue to develop their gastrointestinal tract. Pediatric patients have underdeveloped proteins, which leads to decreased metabolism and increased serum concentrations of specific drugs. However, prodrugs experience the opposite effect because enzymes are necessary in allowing their active form to enter systemic circulation.
Percentage of total body water and extracellular fluid volume both decrease as children grow and develop with time. Pediatric patients thus have a larger volume of distribution than adults, which directly affects the dosing of hydrophilic drugs such as beta-lactam antibiotics like ampicillin. Thus, these drugs are administered at greater weight-based doses or with adjusted dosing intervals in children to account for this key difference in body composition. Infants and neonates also have less plasma proteins. Thus, highly protein-bound drugs have less opportunities for protein binding and leads to increased distribution.
Drug metabolism primarily occurs via enzymes in the liver and can vary according to which specific enzymes are affected in a specific stage of development. Phase I and Phase II enzymes have different rates of maturation and development, depending on their specific mechanism of action (i.e. oxidation, hydrolysis, acetylation, methylation, etc.). Enzyme capacity, clearance, and half-life are all factors that contribute to metabolism differences between children and adults. Drug metabolism can even differ within the pediatric population, separating neonates and infants from young children.