Pediatric Dosage Calculations
Pediatric considerations
• A child’s body may handle a drug differently
in all areas of pharmacokinetics-
absorption, distribution, metabolism and
excretion.
• The responses of the child’s organs to the
effects of the drug also may vary because of
the immaturity of the organs.
Methods of Pediatric dose
a. Clark’s rule
b. Body surface area (BSA)
Clark’s Rule
• Uses the child’s weight to calculate the
appropriate dose and assumes that
the adult dose is based on a 150-lb
person.
• Uses Weight in Lbs, NEVER in Kg
Clark’s Rule
Child’s dose
= Childs Weight (in pounds) x average adult dose
» 150 pounds
Problem
The usual adult dose of Benadryl is 50
mg. What would be the safe dose for a
child weighing 27 lb.
Solutions
= 27 lbs x 50 mg
• 150 lbs.
• = 1,350 mg
• 150
• = 9 mg
Body surface area (BSA): most accurate
method for calculating pediatric dosages
Formula:
child’s dose = Surface area (m2) x adult dose
1.73 m2
Example using BSA
The adult dose is 100 mg/mL. Demerol. The
child weighs 20 kg and is 40 inches tall.
BSA is 0.77m2
Ans:
= 0.77 m2 x 100 mg/ml
1.73 m2
= 77 mg/ml = 44.5 mg/ml
1.73
Dosage based on weight
• Most medications for pediatric clients are
done by child’s weight in order to more
accurately dose.
Example
• A 1.5 year old child is prescribed an
amoxicillin suspension. The dose prescribed
is 40 mg/kg/day divide into equal BID doses.
The suspension is available in a 400 mg/5ml
suspension. What is the dose in ml? The child
weighs 2.2 pounds.
4 Steps to follow:
• Step 1 – Convert pounds to kg.
• Step 2 – Calculate the dose in mg
• Step 3 – Divide the overall dose by the frequency
(BID,TID,etc.)
• Step 4 – Calculate the dose in ml or tablets
• (follow the same formula with adults)
Step 1 – 22 lbs. = 10 kg
2,2 lbs
Step 2 – 10 kg x 40 mg/kg/day = 400 mg/day
Step 3 – 400 mg/day = 200 mg/dose
2 (BID)
Step 4 - D x V - 200 mg x 5 ml
S 400 mg
= 0.5 x 5 ml = 2.5 ml
Calculations of Intravenous
Fluid
Intravenous (IV) solutions (fluids)
consist of a liquid (solvent)
containing one or more dissolved
substances (solutes).
Administration set
• used to deliver a
specified volume
of solution are
different,
depending on the
company
manufacturing the
set.
Macrodrop
• a chamber that
delivers large
drops
• Adult giving sets
and drip
chambers are
calibrated such
that 20 drops of
fluid = 1 mL.
•
Dosage calculation for IV meds
1. Macrodrop
- More commonly used in adult IVF
- In order to calculate the flow rate, need to
know the drop factor: 10, 15, or 20 gtt/mL
Microdrip
-a chamber that
delivers small
drops
All microdrip
chambers deliver
60 drops (gtt) per
mL.
Dosage calculation for IV meds
2. Microdrop
- More commonly used for children, elderly
or critically ill where exact control is
required
- Drop factor is always 60 gtt/mL
• The manufacturer of the macrodrip
administration set has standardized the
drops per milliliter called the drop
factor (DF) for a specific brand of
administration set as follows:
•ACompany Name
specific brand Drop factorset
of administration (gtt/mL) :
as follows
• Abbott 15
• Baxter International 10
• B. Braun 15
• IVAC 20
Calculation of Flow rates
a. Milliliters per Hour (mL/hr)
mL/hr = total number of mL ordered
Number of hours to run
b. Milliliters per Min (mL/min)
mL/min = total mL or volume
total mins to run
Problem
1.Infuse 1000 mL Lactated Ringer’s (LR)
solution over 10 hours.
Sol: ml/hr = 1000 ml
10 hrs
= 100 ml/hr
Calculate the following problems:
Health care Duration
Providers Order of Infusion
Rate(mL/hr)
1000 mL 5% dextrose 12 hrs = ____ mL/hr
in water
1000 mL Lactated 6 hrs. = _____ mL/hr
Ringer’s
500 mL 0.9 sodium 4 hrs = _____ mL/hr
chloride
- pls solve this before turning to the next page---
Solutions:
1. 1000 ml = 83.3 or 83 ml/hr
12 hrs
2. 1000ml = 166.6 or 166 ml/hr
6 hrs
3. 500 ml = 125 ml/hr
4 hrs
Calculating Rates of Infusion for
other than 1 hour
mL/hr= Total volume (milliliters) to infuse x 60 min/hr
Time
Compute:
1. 50 mL 0.9 Na Cl with ampicillin 1 g for 20
mins
2. 150 mL D5W with gentamicin 80 mg to
run for 30 mins
Drops per Minute (gtt/min)
gtts/min= Total volume (mL) to infuse x drop factor
Time (number of mins)
Directions:
- Use a drop factor of 15 gtt/mL for volumes of 100
mL or more per hour;
- Use a microdrip (60gtt/mL) for volumes below
100/hr
Calculate the following
problems
Health care Duration
Providers Order of Infusion
Rate(gtt/min)
• 125 mL D5W 60 min = ___gtt/min
• 100 mL LR 60 min = ___gtt/min
• 50 mL 0.9 NaCl 20 min = ___gtt/min
• - pls solve this before turning to the next page---
Solutions
1. 125 ml x 15 gtts/ml
60 mins
= 1,875 gtts = 31.2 or 31 gtts/min
60 min
2. 100 ml x 15 gtts/ml
60 min
= 1,500 gtts = 25 gtts/min
60 min
3. 50 ml x 60 gtts/ml
60 min
= 3,000 gtts = 150 gtts/min
60 min
Example
• The order is for 1000 mL NS over 8 hours;
drop factor is 10 gtt/mL
• What is your answer?
Solution:
• 1000 ml x 10 gtts/ ml
• 480 mins * * ( 8 hrsx 60 mins = 480 mins)
• = 10,000 gtts
• 480 mins
• = 20 .83 or 21 gtts/min
• The same formula can be used for Ivs
requiring microdrip rates or the following
formulA can be used:
• mL / hr = microdrops / min
• Microdrop – 60 microgtts/ml
• Hour is 60 mins
Example
Order is for 1000 mL D5NS over 24 hours.
Drop factor is 60 gtt/ml
Try solving this!
Solutions
• 1,000 ml x 60 gtts/ ml
• 1,440 mins (24 hrs x 60 mins)
= 60,000 gtts
• 1,440 mins
• = 41.66 or 42 gtss/min
Doctor’s order: Infuse 1200 mL of 0.45 % Normal Saline
at 125 mL/hr. to run 8 hrs.
Drop factor: 12 gtt/min. How many gtt/min will you
regulate the IV?
Try this one! Hope you got it right!!!!
Any
questions???
