2. Age Groups of Pediatrics Population
Group Age
Preterm or premature Less than 36 weeks gestational age
Neonate Less than 30 days of age
Infant 1 month until 1 year of age
Child 1 year until 12 years of age
Adolescent 12 years of age until 18 years of age
3. Oral Drug Absorption in the Neonate vs Older
Children and Adults
Drug Oral Absorption
Acetaminophen Decreased
Ampicillin Increased
Diazepam Normal
Digoxin Normal
Penicillin G Increased
Phenobarbital Decreased
Phenytoin Decreased
Sulfonamides Normal
6. Drug Distribution
• Drug distribution in the neonate depends on
– Amount of body water, body fat and drug binding
• Body water (BW)
– Neonates have more BW than adults (70% vs 50%)
– Full-term: 70% body weight is water
– Pre-term: 85% body weight is water
• Body fat
– Pre-term infants have much less fat than full-term
– Lipid soluble drugs may not be accumulated
• Drug binding to plasma proteins
– Binding of drugs to albumin is reduced
– Drug competition for binding albumin may occur
7. Drug Excretion
• GFR is much lower in newborns than in older
infants, children or adults
• This limitation persists during the first days of
life and improves thereafter
• Neonatal GFR based on body surface area
– Birth: Only 30-40% of the adult value
– 3 weeks: 50-60% of the adult value
– 6-12 months: Reaches adult values
– Thus, renal elimination occurs is very slow initially
• Toddlers
– Have shorter drug elimination (t½) than older
children and adults probably due to ↑ renal
elimination and metabolism
8. Pediatric Dosage Forms
• Elixir
– Alcoholic solutions in which the drug molecules are
dissolved and evenly distributed
– No shaking is required
– Generally, all doses contain equivalent amounts
• Suspension
– Contains undissolved drug particles that must be
distributed throughout the vehicle by shaking
– Caution: Risk of administering unequivalent doses
may lead to toxicity or lack of efficacy
• Prescriber awareness and care giver education
on these differences is important
9. Compliance
• Compliance may be difficult to achieve since it
involves many factors
– Parent’s ability to follow directions
– Measuring errors
– Spilling and spitting out
• Recommendations to improve compliance
– Pill boxes
– Calibrated medicine spoon
– Ask if parent gives another dose after spitting out
– Stress importance of duration of treatment
– Instruct whether to wake the child during q6h dosing
– Give some responsibility to the child for his/her care
10. Pediatric Drug Dosage
• Most drugs approved for use in children have
pediatric doses, stated in mg/kg
• If recommendations are not available, an
approximation can be made by any of several
methods
• Methods include : Age, weight, or surface area
– Age: Young’s rule
– Weight: Clark’s rule
– Doses based on age or weight are conservative
– Doses based on surface area are more adequate
• The calculated pediatric dose should never
exceed the adult dose!
11. Clark’s Rule
• Formula for Clark's Rule is:
Weight of the child in pounds/150 ("normal" adult
weight) X the usual adult dose
• The adult dose of a medication is 30 mg. The child's
weight is 30 lbs. What is the correct dose?
30/150 = 1/5
1/5 x 30 mg = 6 mg
• Preferred method
12. Young’s Rule
• Pediatric doses for children over the age of 2
based on the adult dose. Not as precise as
Clark’s rule.
Take the age of the child in years and divide that
by their age plus 12.
• Multiply this number times the adult dose.
Pediatric dose = [age/(age + 12)] x adult dose
• 2/14 X 250mg = 35 mg for a child age 2 yrs
