PEDIATRIC MEDICATION CALCULATIONS
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Pediatric dosages of medications are given based on weight.
Pediatric dosages are prescribed based on the “safe dose”.
The nurse’s responsibility is to ensure that when administering the medication,
the dose being given is within the safe range.
Safe dosage recommendations can be found in the handbook by Toronto’s
Hospital for Sick Children or in the CPS. We rarely rely on drug handbooks for
finding safe dosages.
Some recommended safe dosages are given as a range, single dose, or
maximum daily dose.
Take a look at the Clindamycin example below.
The safe range is 15-40 mg/kg/day (Most safe doses are “mg/kg/day”)
The minimum safe dose is equal to 15 mg/kg/day
The maximum safe dose is equal to 40 mg/kg/day
So, when the physician prescribes the medication, they will take the child’s
weight and multiple it by somewhere in the safe range of 15 – 40 mg.
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Children of the same weight may be prescribed different dosages of medications
for several reasons.
o The child may have kidney or liver impairment which indicates a smaller
dose be given
o The same antibiotic is given for several different disease processes.
Therefore, a child with meningitis would receive a much higher dose of
the antibiotic than a child with an ear infection.
o The child may have a resistant infection, e.g. chronic ear infection, so the
dose may have to be increased compared to a child with an ear infection
for the first time.
Examples:
Drug
Recommended
Ampicillin
Usual 100 mg/kg/day q6h
Dose limit is 12 gm/day
Ibuprofen
6 mos-12 yrs: 5-10 mg/kg/dose po q6-8 h
Dose limit: 40 mg/kg/day
Clindamycin
15-40 mg/kg/day IV ÷ q6-8h
Maximum
daily
Single
dose
Range
Pediatric Meds – Calculating Safe Dosages
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Most safe dosages are listed in “mg” with the exception being salbutamol
(Ventolin) – it is given in “mL”.
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Terminology in pediatric calculations:
1. Individual safe dose: This is the minimum & maximum “mg” that can be given
in a single dose.
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If the calculation is below the “minimum”, it is considered safe but not
therapeutic.
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If the calculation is above the “maximum”, it is considered unsafe and it
is not administered.
2. Daily safe dose: This is the maximum “mg” that can be given over a 24 hour
period.
3. Amount to be administered: How many “mL” will you administer to the child.
(i.e. in the med syringe)
Rules for Rounding
1. If giving less than 1 mL, calculate to 3 decimal places and round to 2 decimal
places
2. If giving more than 1 mL, calculate to 2 decimal places and round to 1 decimal
place
3. For IV drip rates/mL per hour - calculate to 1 decimal place and round to a whole
number.
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If your calculations show an “unsafe” dose – the medication is NOT TO BE
GIVEN. Notify pharmacy as they have the most current information on the
maximum amount of medication a child can receive.
Pharmacy may tell you that the dose ordered by the physician is safe and to
give it. Document on the chart who you spoke with in Pharmacy and that the
dosage was reviewed with the pharmacist and authorization obtained to
administer the drug.
Pediatric Meds – Calculating Safe Dosages
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Calculations Required for Each Pediatric Question
A. Individual Safe dose:
 Minimum & Maximum (Note: if there is not a “range” given as above for
Ampicillin, you will only need to calculate the maximum.)
 Multiply recommended dose x weight of child
 These calculations are divided by the number of times a day you will give
the medication.
 EXCEPTION: if the med is given as “mg/dose”, such as Ibuprofen.
 You are looking for “mg/dose”.
 The individual safe dose is the amount of “mg” you can safely give per
dose,
e.g. Tylenol 120 mg/dose
 Compare individual ordered dose (mg/dose) to recommended dose
 Physician order must be = or < recommended dose
 Identify if order is “safe” or “not safe”
B. Daily Safe dose:
 You will only use the number at the top of the range given. (E.g. 10 mg for
Ibuprofen)
 Multiply recommended dose x weight of child
 If recommended dose is given as mg/day, no further calculation needed
 If recommended dose is given as mg/dose, multiply by number of doses/day
 You are looking for “mg/day”
 Calculate total daily ordered dose
 Compare total daily ordered dose (mg/dose) to recommended daily dose
 Physician order must be = or < recommended dose
 Identify if order is “safe” or “not safe”
C. Amount to be administered:
 These calculations are the same as for an adult –
 You will need the doctor’s ordered dose and the drug’s available
concentration.
 Pediatric medications are more commonly given as liquid (mL) than as
tablets.
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Parts of Pediatric Question:
Child’s wt – must
include conversion
to kg
Ordered amount –
needed for “amount
to be administered”
calculation
Doctor’s order: Tylenol 150 mg po q8h for an infant weighing 36 pounds.
Recommended daily dose: 22 to 44 mg/kg/day divided q8h. Tylenol is available
in a suspension as 250mg/5ml.
Available from pharmacy
– needed for “amount to
be administered”
calculation
Safe range –
needed for
individual
dose calc. +
daily dose
calc.
How to Complete a Pediatric Medication Question
Remember,
you are
looking for
“mg/dose”
A. Is the ordered individual dose safe?
*You will need to calculate the minimum and maximum individual safe doses.
MIN:
22 mg
kg/day
The
minimum
part of the
range given
36 lbs
1 kg
1 day
2.2 lbs
3 doses
Must put in the
conversion for
lbs to get rid of it
in the equation
22 x 36
792
2.2 x 3
6.6
=
120 mg
dose
Must include how many
doses from the question
i.e. q8h
MAX:
44 mg
Kg/day
36 lbs 1 kg
1 day
2.2 lbs 3 doses
44 x 36
2.2 x 3
1584
=
240 mg/dose
6.6
Dr.’s orders: 150 mg / dose
Recommended Individual: 120-240 mg/dose
The Dr’s order of 150 mg/dose falls into the recommended range. Therefore the
order is SAFE.
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B. Is the ordered daily dose safe?
You only need the
maximum value of the
range
44 mg
36 lbs
Kg/day
1 kg
44 X 36
2.2 lbs
2.2
1584
=
2.2
720
mg/day
Remember,
you are
looking for
“mg/day”
Note: 1 day/3 doses is NOT included – we are
looking for “mg/day”
Dr. Orders: 150 mg x 3 doses in a day = 450 mg / day
Recommended: Maximum of 720 mg / day
The child is receiving less than the
maximum recommended, therefore the order is SAFE.
C. How many mL will you administer?
150 mg
5 mL
250 mg
150 x 5
750
250
250
Pediatric Meds – Calculating Safe Dosages
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=
3 mL
5
Complete the following question:
1. Doctor has ordered Clindamycin 200 mg IV qid for child who weighs 42 lbs.
Recommended safe dose: 15-40 mg/kg/day in divided doses.
Clindamycin is available as 150mg/ml after reconstitution.
A. Is the ordered individual dose safe?
B. Is the ordered daily dose safe?
C. How many mL will you administer?
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A. Safe Individual:
MIN
15 mg
42 lbs
Kg/day
MAX
40 mg
42 lbs
Kg/day
1 kg
1 day
15 x 42
630 = 71.590 = 71.59 mg/dose
2.2 lbs
4 doses
2.2 x 4
8.8
1 kg
2.2 lbs
1 day
40 x 42
4 doses
2.2 x 4
1680 = 190.909 = 190.91 mg/dose
8.8
Dr.’s orders: 200 mg / dose
Recommended Individual: 71.59-190.91 mg/dose
The Dr’s order of 200 mg/dose DOES NOT fall into the recommended range.
Therefore the order is UNSAFE.
B. Safe daily:
40 mg
Kg/day
42 lbs
1 kg
2.2 lbs
40 x 42
1680
2.2
=
763.636 = 763.64 mg/day
2.2
Dr. Orders: 200 mg x 4 doses in a day = 800 mg / day
Recommended: Maximum of 763.6 mg / day
The child is receiving MORE than
the maximum recommended, therefore the order is UNSAFE.
C. Amount to be administered:
NONE as the ordered dose is unsafe.
NOTES:
1. Remember, if the question gives you the child’s weight in kg, you do not need to
include the conversion factor of 1 kg = 2.2 lbs into the equation.
2. If the individual dose turns out to be unsafe, you still need to calculate the daily
dose. Sometimes the physician will order the medication at a higher dose to be given
less frequently over 24 hours which will make it unsafe, but the daily dose could be
calculated to be safe.
3. Do not take your answer for the maximum end of the individual safe dose and
multiply it by the number of times it is being given in order to arrive at your answer
for the daily safe dose. You must perform all of the calculations to arrive at your
answer for the daily safe dose.
4. If you arrive at an unsafe dose, DO NOT show calculations under “Amount to be
administered”. You would not give the drug, so you should not be completing the
calculations.
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