DRUG DOSAGE CALCULATION IN PEDIATRICS: PEDIATRIC DOSAGE DIFFERENT FROM ADULTS FORMULAS: YOUNG, CLARK, DILLING, FRIED RULES BASED ON AGE, BASED ON BODY SURFACE AREA, WEIGHT EXAMPLES. DRUG DOSAGE CALCULATION DAILY FLUID REQUIREMENT CALCULATION OF DRIP RATE INFUSION PUMP FLOW RATE CALCULATION.

1. CRITERIA FOR DRUG
DOSAGE CALCULATION IN
PEDIATRICS
Presented by:
Ms. Manisha Thakur
Child Health Nursing

2. INTRODUCTION
 It is important that you are able to do calculations
confidently, as mistakes may result in the patient
receiving the wrong dose which may lead to serious
consequences for the patient.
 Patient safety depends on accurate I.V., oral drug
dosing; precise calculations are essential to this
process.
 Nurses shouldn't be apprehensive when oral,
parentral drug dosages are presented in practice.

3. PROPER DRUG DOSING OF THE PEDIATRIC
PATIENT
 Proper drug dosing of the pediatric patient
depends on:
1. Age and weight.
2. Overall health status.
3. The condition of such biologic functions as
respiration and circulation.
4. The stage of development of body systems for
drug metabolism (e.g., liver enzymes) and drug
elimination (e.g., renal system).

4. CONT…
 In the neonate, these biologic functions and
systems are underdeveloped:
1. Renal function, for example, develops over the
span of the first 2 years of life.
2. This fact is particularly important because the
most commonly used drugs in neonates, infants,
and young children are antimicrobial agents,
which are eliminated primarily through the
kidneys.
3. If the rate of drug elimination is not properly
considered, drug accumulation in the body could
occur, leading to drug overdosage and toxicity.

5. HOW IS PEDIATRIC DOSAGE CALCULATION
DIFFERENT THAN ADULTS?
 There is no standard dose.
 All doses are based on a recommended dosage
based on: Body weight in kilograms (for this dosage
test) Body Surface Area.

6. CONVERSIONS
 1 teaspoon = 5 mL / cc
 1 tablespoon = 15 mL / cc
 1 ounce = 30 mL /cc
 1 gram (g) = 1000 milligrams (mg)
 1 milligram (mg) = 1000 micrograms (mcg)
 1 liter (L) = 1000 milliliters (mL)
20 Drops per ml

7. MEASURING CUP
HOW MANY ML IN 4 TEASPOONS?
20 ml

8. CONVERSIONS
 How to convert kg into pounds?????
weight × 2.2 = weight in pounds
 How to convert pound into kg?????
weight in pounds
2.2 =weight in kg

9. DOSE CALCULATION
 Dose calculation related to:
1. Young`s rule
2. Dilling`s rule
3. Fried`s rule
4. Clarke`s rule

10. CONT…
 DOSE CALCULATION RELATED TO AGE
Young`s rule =
𝐴𝑔𝑒 (𝑦𝑒𝑎𝑟) /𝐴𝑔𝑒 in 𝑦𝑒𝑎𝑟 + 12 × 𝑎𝑑𝑢𝑙𝑡 𝑑𝑜𝑠e
Example:
if adult dose is 600 mg and child's age is 3 years,
what is C?
C = 600 mg (3 yr / 3 yr + 12)
C = 1800 mg

11. CONT…
Dilling`s rule =
𝐴𝑔𝑒 (𝑦𝑒𝑎𝑟) / 20 × 𝑎𝑑𝑢𝑙𝑡 𝑑𝑜𝑠e
Example:
What will be the dose for the child of 10 years old if
adult dose is 600mg?
=Dose of a child = 10/20 X 600 = 300 mg

12. CONT…
Fried`s rule =
𝐴𝑔𝑒 (𝑚𝑜𝑛𝑡hs) / 150 × 𝑎𝑑𝑢𝑙𝑡 𝑑𝑜𝑠e

13. CONT…
 DOSE CALCULATION RELATED TO BOGY
WEIGHT
 Clarke`s rule =
𝐵𝑜𝑑𝑦 𝑤𝑒𝑖𝑔h𝑡 𝑙𝑏 /150 × 𝑎𝑑𝑢𝑙𝑡 𝑑𝑜𝑠𝑒

14. CONT…
DOSE CALCULATION RELATED TO BODY
SURFACE AREA
𝐶h𝑖𝑙𝑑 𝑑𝑜𝑠𝑒 =
𝐶h𝑖𝑙𝑑`𝑠 𝑏𝑜𝑑𝑦 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎/𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑎𝑑𝑢𝑙𝑡`𝑠 𝑏𝑜𝑑𝑦
𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 × 𝑎𝑑𝑢𝑙𝑡`𝑠 𝑑𝑜𝑠e

15. DAILY FLUID NEEDS
 Fluid needs should be calculated on every patient
to assure that the infant / child is receiving the
correct amount of fluids.
 Standard formula for pediatrics needs to be
memorized.

16. IV FLUID CALCULATIONS
 The maintenance dose for administration of IV
fluids is based on the following formula
 100 mL of fluid for the 1st 10 kg of weight
 50 mL of fluid for the 2nd 10 kg of weight
 20 mL of fluid for and additional kg

17. CONT…
 Example:
 Jose weighs 16 pounds
 Weight in kg = 7.27 kg
Using the formula provided how many ml of fluid would
he need in 24 hours.
 Fluid Calculation 7.27 kilograms
 100 mL x 7.27 kg = 727 mL
727 mL / 24 hours or mL per hour
30 ml/hour

18. CONT…
 Fluid Calculation 64 pound child
Convert pounds to kilograms =29.09 kg
 Fluid calculations:
 100 mL x 10 kg = 1000 mL
 50 ml x 10 kg = 500mL
 20 ml x 9.09 kg = 181 mL
 1681 mL / 24 hours or mL / hour
 70ml/hour

19. CONT….
 Fluid calculations can be rounded. You cannot
administer a fraction of a mL.
 In child #1 the calculated hourly rate of 29.7 would
be rounded to 30 mL / hour
 In child #2 the calculated hourly rate of would be
rounded to 70 mL / hour.

20. CONT…
 Since children are in the hospital for various
illnesses they will often have increased fluid needs:
dehydration, fever, vomiting, diarrhea, inability to
take fluids.
 24 hour fluid calculations may be 1 ½ to 2 times
maintenance.

21. CONT…
 In Child number #1 maintenance fluid needs are
713 mL / 24 hours.1 ½ time maintenance would be
713 x 1.5 = 1069 mL / 24 hours or 45 mL / hour.
 In child # 2 maintenance fluid needs are 1681 mL /
24 hours.1 ½ times maintenance would be 1681 x
1.5 = 2522 mL / 24 hours or 105 mL / hour.

22. CALCULATION OF DRUG DOSAGE &
DROP RATE
 Hourly recording of IV fluid intake.
 Don’t try and catch up on fluids.
 Calculate fluids used to administer IV medications
into the hourly fluid calculations.

23. CONT….
 Drug dose – it is sum of the amount ordered divided by
total amount an multiplied by volume.
Amount ordered (mg) × volume (ml)
Actual amount (mg)
Example:
Inj. Cefotaxim 250 mg iv BD. Calculate drug dose…?
250 mg × 2.5 ml
250 mg
Answer: 2.5ml.

24. ON THE BASIS OF BODY SURFACE AREA
adult dose × surface area of child in m2
1.8 = child dose
 Costeff,s formula
4 × weight + 7
Weight+ 90 = body surface area of child in m2

25. APPROXIMATE BODY SURFACE AREA

26. CONT…
 In case the calculated amount is less than 1ml,
then….
 Amount ordered (mg) × volume (ml) × 40 units
Actual amount (mg)

27. EXAMPLE….
 Inj. Rantac 10 mg IV BD…. Calculate drug dose…?
 10 × 2 × 40
50
o 16 units.

28. CONT….
Macrodrip tubing administers a larger drop and may
be used for 10 gtts/mL, 15 gtts/mL or 20 gtts/mL.
Microdrip tubing administers 60 gtts/mL. These are
called drop factors.
The drop factor is the number of drops contained in 1
milliliter.

29. CALCULATION OF DRIP RATE
Amount of fluid in ml / total time of infusion in min. X
drop factor (gtts/ml) = I/V infusion rate
Note: drops are always rounded to nearest whole no.

30. CONT…
Example: The physician has ordered D5W 1200 milliliters in
12 hours using 15 drops per milliliter infusion rate. What is
the IV infusion rate in drops per minute?
Given:
Amount of fluid: 1200 mL
Total time of infusion: 12 hrs
Administration set drop factor: 15 gtts/mL
IV infusion rate: ? gtts/min
Step 1: Convert 12 hours into minutes.
12 hrs x 60 min/hr = 720 min
Step 2: Use the formula above to calculate the IV infusion rate.
IV infusion rate = 1200 /720 x 15 = 100/4 = 25
Therefore, the IV infusion rate is 25 drops per minute.

31. DRUG DOSAGE CALCULATION
Formula:
Amount DESIRED (D)/ Amount on HAND (H) X
QUANTITY (Q) = Y (Tablets Required)
Note: When medication is given in tablets, the
QUANTITY = 1 since the amount of medication
available is specified per (one) tablet.

32. INFUSION PUMP
 Infusion pumps do not have a calibrated drop
factor.
 The flow rate depends on the volume of fluid
ordered and the time of infusion.
FORMULA:
Volume (ml)/ time (h) = (Flow rate in ml/hr)

33. CONT:
 Step 1: Determine your givens.
 Volume: 1200 mL
 Time: 10 h
 Step 2: Since the volume is given in mL and the
time is given in hours, the flow rate can be
calculated in one step using the formula.
 Volume (ml)/ time (h) = (Flow rate in ml/hr)
 Step 3: Use the formula to calculate the IV flow
rate (gtts/min).
 1200 (ml) = 120 ml/hr 10 (h)

34. PREPARING PARENTERAL MEDICATION FROM DRUG
SUPPLIED AS A POWDER (RECONSTITUION)
On the drug label or the package insert will state the
diluents to be used and the exact amount to be added.
When adding a solution or diluents to the powder, you
will notice that the directions will state the volume and
dose after the solution has been added.