Pediatric dose calculations can be complex due to the physiological differences between children and adults, which can impact drug pharmacokinetics and pharmacodynamics.
There are several methods used to determine the appropriate pediatric dosage based on factors such as age, body weight, and body surface area (BSA).
Age-Based Dosing Methods
1) Young's Formula (For children aged 2-12 years):
Formula:
Pediatric dose = (Age of child / (Age of child + 12)) x adult dose
2) Dilling's Formula (For infants under 1 year):
Formula:
Infant dose = (Age in months / 24) x adult dose
3) Cowling's Rule (For children aged 1-14 years):
Formula:
Pediatric dose = (Age of child / (Age of child + 16)) x adult dose
4) Freud's Formula (For infants and children under 2 years):
Formula:
Pediatric dose = (Age in months / 150) x adult dose
Note: Age-based methods are less accurate than weight- or BSA-based methods.
Weight-Based Dosing Method
1) Clark’s formula
Based on the child's weight in pounds.
Formula:
Pediatric dose = (Weight in pounds / 150) x adult dose
Example: If a child weighs 50 pounds and the adult dose is 300 mg, the pediatric dose is:
Pediatric dose = (50 / 150) x 300 mg = 100 mg
Note: While more accurate than age-based methods, weight-based dosing still has limitations and should be cross-checked with guidelines.
Body Surface Area (BSA)-Based Dosing
BSA-based dosing is more precise as it considers both weight and height, reflecting the child’s overall physiological development.
Mosteller Formula (to calculate BSA):
BSA (m²) = √[(Height in cm x Weight in kg) / 3600]
Pediatric Dose Formula (using BSA):
Pediatric dose = BSA x Dose per m²
Example: If the child's BSA is 0.8 m² and the recommended dose is 100 mg/m², the pediatric dose is:Pediatric dose = 0.8 m² x 100 mg/m² = 80 mg