Paediatrics

• When do we consider the foetal development is completed?

  • Once the baby is born
• What is the definition of gestational age?

  • Gestational age is the term used to describe how far along pregnancy you are, from the first day of the women's last menstrual cycle
• What is postnatal age?

  • Age from the day of delivery (birth)
• What is the age of a preterm neonate?

  • Born at <37 weeks gestation
• What is the age of a term neonate?

  • Born at 37 to 42 weeks gestation
• What is the age of a post-term neonate?

  • Born at >/or equal to 42 weeks gestation
• What is the age of a preterm newborn, very preterm and extremely preterm?

  • Preterm newborn: less than 37 weeks gestation
  • Very preterm: 28 to 32 weeks
  • Extremely preterm: less than 28 weeks
• What is the age of a neonate?

  • 0 - 27 days
• What is the age of infant and toddlers?

  • 28 days to 23 months
• What is the age of children?

  • 2 - 11 years
• What is the age of adolescents?

  • 12 to 16 - 18 (no consensus obtained)
• What is physiology?

  • Physiology is the study of functions and mechanisms which work within a living system
• The developmental changes occurring during pediatric life will influence the pharmacology of medicines
• Factors that influence the developmental changes in physiology of pediatrics:

  • Changes in body composition
  • Changes in body proportion
  • Developmental changes in physiology with pathophysiology
  • Changes in drug disposition by major organs of metabolism and elimination (ADME)
  • Development and function of drug targets (enzymes, transporters, receptors, channels)
  • Environmental influences
• What is pharmacodynamics?

  • What a drug does to the body
  • Mechanism of action
  • Drug receptor protein signaling
  • Dose-response
• What is pharmacokinetics?

  • What the body does to a drug
  • ADME (absorption, distribution, metabolism, excretion)
• Changes in body composition with growth and aging over time:

  • Water composition goes down over time
• How do fluid and fat volumes change with age?

  • Total body water and extracellular fluid volume decrease with age
  • This affects drug dosing, especially for water-soluble drugs like aminoglycosides
• Body Proportion:

  • The CNS in newborn babies is predisposed to higher concentrations of medicines than infants
  • This is because newborn infants have a relatively large head circumference and cranial volume, leading to higher drug concentrations
• What can lead to toxic gasping syndrome?

  • Neurotoxic excipients in certain medicines, such as benzyl alcohol in clozapam IV, can cause toxic gasping syndrome in premature babies
• What is bioavailability?

  • Bioavailability is the fraction of an administered dose of unchanged drug that reaches the systemic circulation
• What mode of administration can be erratic (unpredictable)?

  • Enteral administration via the GIT can be erratic, especially in newborns
• What route of administration ensures maximum bioavailability?

  • Intravenous route ensures maximum bioavailability, especially in hospital settings where rapid outcomes are required
• Factors that influence oral absorption:

  • Gastric and intestinal pH
  • Gastric and intestinal transit time
  • Gastrointestinal content
  • Disease/illness
  • Immature biliary secretion
• What drugs are given by the rectal route in newborn children?

  • Paracetamol for pain relief
  • Diazepam for seizures
• Properties of rectal absorption in pediatrics:

  • Reserved for when oral or IV routes are not available
  • Rapid onset of action
  • Some products may be erratically absorbed
  • Some drugs may irritate the rectal mucosa
  • Examples of use: pain relief, constipation, epilepsy
• Properties of subcutaneous absorption in pediatrics:

  • Can be painful, used for administering insulin
• Properties of intramuscular absorption in pediatrics:

  • Should be avoided in children
  • Absorption in infants and children after IM injection is faster than in neonates
• Properties of percutaneous absorption in pediatrics:

  • Topical absorption
  • Skin is painless and non-invasive
  • Higher topical absorption in neonates and young infants
• Factors that affect distribution in paediatrics:

  • Vascular perfusion
  • Body composition
  • Tissue binding characteristics
  • Plasma protein binding
• Properties of plasma protein binding in pediatrics:

  • Less protein binding in neonates
  • Levels of protein binding are similar to adults for acidic drugs by 3 years old, for basic drugs by 7-12 years old
• Properties of subcutaneous absorption in pediatrics:

  • Can be painful, used for administering insulin