Paediatrics Flashcards
Define the differences in age classification of premature baby and a full term baby?
A premature baby is a born before 37 weeks whereas a full term baby is considered between 38-42 weeks.
What is the different age classifications from neonate to young adult/adolescent?
Neonate: less than 1 month old
Infant: less than a year old
Child: between 1-12 years
Young adult/adolescent: between 13-19 years
Why are these particular age classifications used? Give an example.
They are used to reflect the important biological changes that occur at these ages. For example a premature baby has significant different pharmacokinetic profile in comparison to a full term baby. Premature babies have a higher skin permeability in comparison to full term babies and therefore would have increased transdermal absorption.
Lung maturation has not also full developed in premature babies and also has a higher percentage of body water: body weight ratio.
At what age is adult dosing considered?
Usually from the age of 12 however some children at this age will be still pre-pubescent and will not developed into their adult weight/height.
In relation to absorption, how does the gastric pH differ in paediatrics?
From birth to 2-3 years the gastric pH is around 6-8 to which then it reaches the adult gastric pH of 2-3, differing depending on whether the stomach is empty or full.
What is an additional consideration to make regarding acid secretion in premature babies?
Premature babies have an immature gastric mucosa meaning that they have reduced gastric acid secretion. In application to drugs, as if they are acid labile there will be increased absorption within the gastrointestinal tract as the drug won’t be ‘destroyed’ in acidic conditions.
How does gastric emptying time differ in paediatrics?
In neonates (less than a month) and young infants (less than a year) gastric emptying and gastrointestinal transit time is prolonged meaning that the rates of absorption are slower. However the transit time does increase with age.
What condition often affects children in relation to the GI tract?
Acute diarrhoea, if prevalent may need to change the route of administration of medication as will lead to reduced absorption.
In relation to absorption, does the pharmacokinetic profile of rectal medication differ in children?
There can be some variation in rate and extent of absorption, similarly to oral route - can be unreliable however for drugs with a rapid onset of action such as Diazepam, it can be beneficial especially if the child is fitting or vomiting and unable to take medication orally.
In relation to absorption, does the pharmacokinetic profile of topical medication differ in children?
Percutaneous absorption is related to the thickness of the stratum corneum, in newborns and young children this layer is reduced due to a immature epidermal barrier. They also have increased skin hydration, both of which contribute to an increased risk of adverse skin reactions.
Children also have a higher S.A to body weight ratio.
In relation to absorption, does the pharmacokinetic profile of intramuscular medication differ in children?
This route of administration is usually avoided in children due to the discomfort it causes. If used in neonates there is a slower I.M absorption due to reduced blood flow to the muscle.
Why would dosing of water soluble drugs be greater in neonates and infants?
Total body water and ECF decreases with age and therefore the greatest distribution for water soluble drugs is with neonates and infants, resulting in a higher dose on a weight to weight bases in comparison to adults. Examples of water soluble drugs include Gentamicin and Theophylline.
How does protein binding differ in paediatrics and adulthood?
In infancy (first year) they have lower protein binding (as they have lower albumin and total protein concentrations). However this is not a significant clinical difference.
How does metabolism of drugs differ in paediatrics?
At birth, enzymatic systems are absent or are at low concentrations then there is a dramatic increase in metabolic rate in older infants and in young children resulting in higher mg/kg dosing requirements. For example in children (1-9 years) the dosing of Theophylline is 24mg/kg however in adults it is only 13mg/kg. Other drugs where there are higher mg/kg due to increased metabolic rate include Carbamazepine and Phenytoin.
How does elimination of drugs differ in paediatrics?
Renal clearance is limited at birth but is dependent upon the gestational age. However renal clearance increases rapidly and are considered to be adults by 3 months. Tubular reabsorption however matures more slowly and is considered to be that of an adult’s at 7 months.
What is grey baby syndrome?
Grey baby syndrome is a toxic reaction to chloramphenicol, where there is a reduced ability to conjugate the drug and excrete its active form in the urine. The levels therefore builds up causing toxicity.
How do elimination half lives vary in children compared to adults?
The elimination half lives are much shorter in children than in adults due to enzymes responsible for drug reaction being reduced/absent at birth but quickly develop to have an increased rate compared to adults, therefore increased doses/dosing frequency is required.
