[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › Paediatric and perinatal pharmacology # Paediatric and perinatal pharmacology Why newborns and children handle medicines differently from adults, why doses are based on weight, and which drugs are risky at each age. Updated Nov 2, 2026 Children are not small adults. In the newborn, body water, protein binding, liver enzymes and kidney function are all immature, and they change quickly over the first months of life. Several well-known drug disasters in babies came from ignoring these differences, and they still shape today's labels. ## Key points - Newborns have more body water, less albumin and immature liver conjugation and kidney filtration, so many drugs last longer and reach higher levels. - Doses in children are calculated by weight (or body surface area) and checked against age-specific ranges; dose errors are a leading paediatric safety problem. - Chloramphenicol can cause the grey baby syndrome because the newborn cannot clear it; ceftriaxone is avoided in jaundiced neonates and must not meet calcium-containing infusions in neonates. - Codeine is contraindicated in children under twelve because ultra-rapid CYP2D6 metabolisers can make dangerous amounts of morphine. - Aspirin is avoided in children and teenagers with viral illness because of Reye's syndrome; tetracyclines stain developing teeth. ## How the newborn handles drugs - Absorption: gastric acid and emptying differ from adults, and the skin absorbs topical products easily. - Distribution: more total body water and less fat; lower albumin, so more free drug and bilirubin can be displaced. - Metabolism: glucuronidation and several CYP enzymes are immature at birth and mature over months. - Elimination: glomerular filtration is low at birth, especially in preterm babies, and rises quickly in the first weeks. ## Classic neonatal toxicities Chloramphenicol given in the first days of life accumulated because of immature liver and kidney function and caused the grey baby syndrome: abdominal distension, ashen cyanosis and circulatory collapse. Ceftriaxone can displace bilirubin from albumin and is not used in jaundiced neonates or in premature babies below a set postmenstrual age; in neonates it must not be combined with intravenous calcium-containing solutions, because fatal precipitates have formed in the lungs and kidneys. ## Codeine, aspirin and tetracyclines Codeine works by being converted to morphine by CYP2D6. Children who are ultra-rapid metabolisers can make too much morphine, and deaths from respiratory depression led to a contraindication below twelve years and after tonsil or adenoid surgery in those under eighteen. Aspirin given to a child or teenager with chickenpox or influenza can cause Reye's syndrome. Tetracyclines given while teeth are forming (late pregnancy to about eight years of age) can permanently discolour them. ## Weight-based dosing and error prevention Paediatric doses are worked out from weight and age, which multiplies the chance of calculation and decimal errors, especially with liquid medicines and concentrated injections. Safe practice includes recording the weight in kilograms, double-checking calculations, using oral syringes or marked dosing cups rather than kitchen spoons, and choosing products labelled for the child's age. Adult products should not be given to children. ## Adolescents Adolescents usually handle drugs like adults, but adherence, confidentiality, contraception and risky use of alcohol and other drugs need attention. ## Memory aid Neonates are WET, LOW and SLOW: WET (more water), LOW (low albumin), SLOW (slow liver and kidney). ## Test yourself Think of the answer, then tap the question to see it. ## Why does chloramphenicol cause the grey baby syndrome? The newborn's immature liver and kidneys cannot clear it, so blood levels rise with each dose and cause circulatory collapse. ## Why is codeine contraindicated in young children? Ultra-rapid CYP2D6 metabolisers convert too much codeine to morphine, which has caused fatal respiratory depression. ## Why does ceftriaxone need caution in neonates (two reasons)? It displaces bilirubin from albumin (risk in jaundiced or premature babies), and it precipitates with intravenous calcium-containing solutions. ## Why is aspirin avoided in a child with chickenpox or flu? Because of the risk of Reye's syndrome. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/pharmacology/topics/paediatric-and-perinatal-pharmacology/) [More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology) ## Example drugs - [Chloramphenicol](https://durgical.com/en/pharmacology/chloramphenicol/) - [Ceftriaxone](https://durgical.com/en/pharmacology/ceftriaxone/) - [Codeine](https://durgical.com/en/pharmacology/codeine/) - [Acetylsalicylic acid](https://durgical.com/en/pharmacology/acetylsalicylic-acid/) - [Tetracycline](https://durgical.com/en/pharmacology/tetracycline/) - [Paracetamol](https://durgical.com/en/pharmacology/paracetamol/) - [Gentamicin](https://durgical.com/en/pharmacology/gentamicin/) ## Connections ## Related classes 4 - [Tetracyclines](https://durgical.com/en/pharmacology/classes/tetracyclines/) - [Opioids and antagonists](https://durgical.com/en/pharmacology/classes/opioids-and-antagonists/) - [Nonsteroidal anti-inflammatory drugs (NSAIDs)](https://durgical.com/en/pharmacology/classes/nonsteroidal-anti-inflammatory-drugs/) - [Non-opioid analgesic antipyretics](https://durgical.com/en/pharmacology/classes/non-opioid-analgesic-antipyretics/) [← All of pharmacology](https://durgical.com/en/pharmacology/) Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given. Sources: [DailyMed - CHLORAMPHENICOL SODIUM SUCCINATE- chloramphenicol sodium succinate injection, powder, lyophilized, for solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=aed29594-211d-49ef-813f-131975a8d0e3) (DailyMed (U.S. National Library of Medicine), 2026); [DailyMed - CEFTRIAXONE injection, powder, for solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8351aa37-552d-471d-b293-c564dcb6ec29) (DailyMed (U.S. National Library of Medicine), 2026); [DailyMed - CODEINE SULFATE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5819bdf7-300e-45b8-8f3a-447b53656293) (DailyMed (U.S. National Library of Medicine), 2026); [Aspirin: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682878.html) (MedlinePlus (U.S. National Library of Medicine), 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/topics/paediatric-and-perinatal-pharmacology/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/topics/paediatric-and-perinatal-pharmacology/