The dose of a drug for a child can be calculated from the adult dose based on age, weight and surface area of the child. Here, we will learn to calculate the child dose from the adult dose with practical examples.
Dose Proportionate to age
Based on age, the child’s dose can be calculated by using the following formulas,
- Young’s Rule
- Dilling Rule
- Cowling’s Formula
- Freid’s Formula
Let’s have a look at calculating by using examples.
Young’s Rule
The formula to calculate the child dose from the adult dose is given as follows,
Child’s Dose = Age in years × adult dose
Age in years+12
Example
Suppose that we want to calculate a dose for a 6-year-old child from an adult dose of 60 mg.
Put values in the above formula
Child’s Dose = 6 × 60
6+12
Child’s Dose = 6 × 60 = 20 mg
18
Conclusion
A 20 mg dose will be required for a 6-year-old child if the adult dose is 60 mg.
Dilling Rule
The formula used is,
Child’s Dose = Age in years × adult dose
20
Example
If we want to calculate a dose for a 6-year-old child from an adult dose, which is 60 mg.
Put values in the above formula
Child’s Dose = 6 × 60
20
Child’s Dose = 6 × 60 = 18 mg
20
Conclusion
An 18 mg dose will be required for a 6-year-old child if the adult dose is 60 mg.
Cowling’s Formula
The formula to calculate the child dose from the adult dose by Cowling’s formula is given as follows,
Child’s Dose = Age in years+1× adult dose
24
Example
If we want to calculate a dose for a 6-year-old child from an adult dose, which is 60 mg.
Put values in the above formula
Child’s Dose = 6+1 × 60
24
Child’s Dose = 7 × 60 = 17.5 mg
24
Conclusion
A 17.5 mg dose will be required for a 6-year-old child if the adult dose is 60 mg.
Freid’s Formula
The following formula is used,
Child’s Dose = Age in month × adult dose
150
Example
If we want to calculate a dose for a 10-month-old child from an adult dose, which is 60 mg.
Put values in the above formula
Child’s Dose = 10 × 60 = 4 mg
150
Conclusion
A 4 mg dose will be required for a 10-month-old child if the adult dose is 60 mg.
Based On Body Weight
Clark’s Formula is used.
Clark’s Formula
This formula is used to calculate the dose of a child based on body weight.
The formula to calculate the child dose from the adult dose by Clark’s Formula is given as follows,
Child’s Dose = child weight (kg) × adult dose
70
Example
Calculate the dose for a 6-year-old child having 15 kg body weight and the adult dose is 60 mg.
Put values in the above formula
Child’s Dose = 14× 60
70
Child’s Dose = 14 × 60 = 12 mg
70
Conclusion
A 12 mg dose will be required.
Dose Proportional to surface area
To calculate child dose based on surface area, the following formula is used
Surface area of child×100 = %age adult dose Surface area of adult dose.
Also Read