Medical Office Pharmacology: Review For Medical Assistant Students and Professionals
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More Calculations—Pediatric Rules
For medical assistants who need to brush up on certain areas in pharmacology as it applies to a medical office.
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medication dosage calculations  More Calculations—Pediatric Rules...

More Calculations—Pediatric Rules
Calculation of Pediatric Doses:
Dosages for children are generally based on body size and weight. Interesting and worth knowing is that almost all reference manuals give adult dosages of medications, unless they are specifically designed for the pediatric patient. When an extremely large or small patient requires a medication, the dosage should be adjusted accordingly, not just administered indiscriminately.

Dosages should also be reduced for elderly, frail, and debilitated patients!
There are several tools available to adjust a medication dosage. The use of West’s nomogram will provide the medical staff with the patient’s overall body surface area based on height and weight. This is a reliable method for when the doctor has ordered an antibiotic whose average adult dose is 250 mg per day for a child who is 120 cm tall and weighs 40 kg. The first step of this equation would be to determine the child’s body surface area (BSA) using the West nomogram.

Medical assistant takes notes!Consider the following:
The rule governing calculation of pediatric doses for newborns and young infants with a normal lean body mass and normal body development is Clark's Rule. For toddlers use Fried’s Rule, and for older children Youngs Rule is used.

Using a straight edge (such as a ruler or piece of paper), align the straight edge so that it intersects exactly at the child's height and weight. Doing so will create an intersection in the BSA scale. The boxed in scale is to be used only if the child is of normal height and weight.

Then use the following formula:
x adult dose = approx. child dose
(That's: Child's BSA divided by 1.73 timed by adult dose)

In the calculation of dosages, weight has a more direct bearing on the dose than any other factor, especially in the calculation of pediatric doses.

1. Clark's Rule for Infants or Children:
Clark’s rule is based upon the weight of the child. To determine the proper dosage for children, divide child’s weight in pounds by 150 to get the correct fraction of adult dose. Example: For a 50 pound child give 50/150 (or 1/3) of the adult dose. Therefore, if the adult dose is 30 drops taken 3 times per day, the child’s dose will be 10 drops taken 3 times per day (not 30 drops taken 1 time per day!)

(Weight in pounds x (Adult dose)
(That's: Child's weight in pounds times adult dose divided by 150)

2. Fried's Rule for Infants and Children up to 1 to 2 Years:

(Age in Months) x (Adult Dose)
(That's: Child's age in months times adult dose divided by 150)

3. Young's Rule for Children from 1 year to 12 Years:
Young’s rule is based upon the age of the child, regardless of its weight. It is a “rule of the thumb” method for calculating the dose of medicine to be administered to a child. The child’s age divided by age plus 12 represents the fraction of the adult dose suitable for the child.

(Age in Years) x (Adult Dose)
(That's: Child's age in years times adult dose divided by child's age plus 12)
Age + 12

Attention! Every medical caregiver, including the medical assistant needs to be familiar with these rules! Please copy them and memorize.


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