Editing Pediatrics (section)

==Differences between adult and pediatric medicine==
The body size differences are paralleled by maturation changes. The smaller body of an [[infant]] or [[neonate]] is substantially different physiologically from that of an adult. Congenital defects, genetic variance, and developmental issues are of greater concern to pediatricians than they often are to adult physicians. A common adage is that children are not simply "little adults". The clinician must take into account the immature physiology of the infant or child when considering symptoms, prescribing medications, and diagnosing illnesses.<ref name=":0">{{Cite journal |last=O'Hara |first=Kate |date=2016 |title=Paediatric pharmacokinetics and drug doses |journal=Australian Prescriber |volume=39 |issue=6 |pages=208–210 |doi=10.18773/austprescr.2016.071 |issn=0312-8008 |pmc=5155058 |pmid=27990048}}</ref>

Pediatric physiology directly impacts the [[Pharmacokinetics|pharmacokinetic]] properties of drugs that enter the body. The [[Absorption (pharmacology)|absorption]], [[Distribution (pharmacology)|distribution]], [[Drug metabolism|metabolism]], and [[Drug elimination|elimination]] of medications differ between developing children and grown adults.<ref name=":0" /><ref name=":1" /><ref name=":2" /> Despite completed studies and reviews, continual research is needed to better understand how these factors should affect the decisions of healthcare providers when prescribing and administering medications to the pediatric population.<ref name=":0" />

=== Absorption ===
Many drug absorption differences between pediatric and adult populations revolve around the stomach. Neonates and young infants have increased stomach [[pH]] due to decreased [[Gastric acid|acid]] secretion, thereby creating a more basic environment for drugs that are taken by mouth.<ref name=":1">{{Cite journal |last1=Wagner |first1=Jonathan |last2=Abdel-Rahman |first2=Susan M. |date=2013 |title=Pediatric pharmacokinetics |journal=Pediatrics in Review |volume=34 |issue=6 |pages=258–269 |doi=10.1542/pir.34-6-258 |issn=1526-3347 |pmid=23729775}}</ref><ref name=":0" /><ref name=":2" /> 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.<ref name=":1" />

Children also have an extended rate of gastric emptying, which slows the rate of drug absorption.<ref name=":1" /><ref name=":2" />

Drug absorption also depends on specific [[enzyme]]s 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.<ref name=":1" /><ref name=":2" /> Pediatric patients have underdeveloped [[protein]]s, which leads to decreased metabolism and increased serum concentrations of specific drugs. However, [[prodrug]]s experience the opposite effect because enzymes are necessary for allowing their active form to enter systemic circulation.<ref name=":1" />

=== Distribution ===
Percentage of [[total body water]] and [[Extracellular fluid|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 [[Hydrophile|hydrophilic]] drugs such as [[Β-lactam antibiotic|beta-lactam antibiotics]] like ampicillin.<ref name=":1" /> 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.<ref name=":1" /><ref name=":0" />

Infants and neonates also have fewer plasma proteins. Thus, highly protein-bound drugs have fewer opportunities for protein binding, leading to increased distribution.<ref name=":0" />

=== Metabolism ===
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.<ref name=":1" /> 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 (pharmacology)|clearance]], and [[half-life]] are all factors that contribute to metabolism differences between children and adults.<ref name=":1" /><ref name=":2">{{Cite journal |last1=Batchelor |first1=Hannah Katharine |last2=Marriott |first2=John Francis |date=2015 |title=Paediatric pharmacokinetics: key considerations |journal=British Journal of Clinical Pharmacology |volume=79 |issue=3 |pages=395–404 |doi=10.1111/bcp.12267 |issn=1365-2125 |pmc=4345950 |pmid=25855821}}</ref> Drug metabolism can even differ within the pediatric population, separating neonates and infants from young children.<ref name=":0" />

=== Elimination ===
Drug elimination is primarily facilitated via the liver and kidneys.<ref name=":1" /> In infants and young children, the larger relative size of their kidneys leads to increased [[renal]] clearance of medications that are eliminated through urine.<ref name=":2" /> In [[Preterm birth|preterm]] neonates and infants, their kidneys are slower to mature and thus are unable to clear as much drug as fully developed kidneys. This can cause unwanted drug build-up, which is why it is important to consider lower doses and greater dosing intervals for this population.<ref name=":0" /><ref name=":1" /> Diseases that negatively affect kidney function can also have the same effect and thus warrant similar considerations.<ref name=":1" />