Clarks rule and Youngs rule

Clark's rule   |   Young's rule   |  mg/kg/day




Clark's rule
and
Young's rule
are two of several different methods of calculating pediatric dosages.

These methods are used when either the manufacturer has not recommended dosages for children or the prescriber has requested them to be used. The best explanation for these is simply that children vary so much in weight, size, tolerances, etc.

Clark's Rule

Clark's Rule uses Weight in Lbs, NEVER in Kg.

Here is the formula:

Adult Dose X (Weight ÷ 150) = Childs Dose

Example
11 year old girl / 70 Lbs

500mg X (70 ÷ 150) = Child's Dose

500mg X ( .47 )= Child's Dose

500mg X .47 = 235mg

Child's Dose = 235Mg


Clark's rule video tutorial
By Zita Schmitt, CPhT


Young's Rule

Youngs Rule uses age.
(which makes it easier to remember, the word young refers to age)

Here is the formula:

Adult Dose X (Age ÷ (Age+12)) = Child's Dose

Example
11 year old girl / 70 Lbs

500mg X (11 ÷ (11+12)) = Child's Dose

500mg X (11 ÷ 23) = Child's Dose

500mg X .48 = Child's Dose

Child's Dose = 240mg


Young's rule video tutorial
By Zita Schmitt, CPhT


Dosage based on weight

Often drugs are prescribed based on an adults or childs weight in order to more accurately dose. The calculation is very simple and easy to perform. However, you must pay close attention to whether the dosage has been prescribed per Kg or Lbs.

Example:
132 Lb woman is prescribed Acyclovir 5mg/kg

First convert Lbs. to Kg

(132 ÷ 2.2) = 60kg

The prescription calls for 5mg per kg

60 x 5mg = 300mg


Mg/Kg/Day video tutorial
By Zita Schmitt, CPhT








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Accurate dosage calculations are very important in pharmacy. The tutorial on this website is strictly for the purpose of practicing and preparing for the PTCB or ExCPT exams. Pharmacy Technicians are relied on to calculate standard and non-standard dosages every day. However, a pharmacist is ultimately responsible for all medications and will have the final call on which methods, formulas and calculations are to be used. This website is for informational, educational and entertainment purposes only. Always consult a licensed medical doctor or pharmacist before determining any dosage calculation. If you have any questions, please use the contact page
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