Pediatric Dosage Calculation

Professor Shaffer 2012-2013

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

Begin by Converting to Kilograms

• All MD orders will be ordered as a dose per kg

• Convert the patient’s weight in lbs to kg by dividing the weight in lbs by 2.2

• Example:50 lbs divide by 2.2 = 22.7272727272727

Round to tenths place = 22.7 kg

Now you try!

1. Patients weight 48 lbs

How many kg does the patient weigh?

Patient weight 13.9 lbs

How many kg does the patient weigh?

The MD order The MD order can be written in several

ways:• In a daily total (dose not specified) after

further calculation to be divided in equal doses

Ex: 30mg/kg/day administer orally equally divided in three doses

or• Per dose

Ex: 15mg/kg administer orally twice daily

Lets Try it!

Patients weight: 45 lbs

2. Give 30mg/kg/day administer orally equally divided into three doses

How many mg per dose? How much is the 24 hr drug total?

3. Give 30mg/kg administer orally in three divided doses

How many mg per dose? How much is the 24 hr drug total?

Is the dose safe?

• All pediatric dosages have a recommended range in the drug guide

• These ranges are typically based on a 24 hour total amount of a dosage in mg, mcg, gm, etc.

• Remember how to convert mcg to mg, gram to mg etc.

Is the order safe?

• A statement from the drug guide will be provided on the dosage assessment test

Ex: The drug guide states the recommended safe dosage is 3-5 mg/kg/day to be administered orally in 2 divided doses

Lets try it!

4. MD order Sporanox (itraconazole) 40 mg administer orally twice dailyPatients weight 47 lbs

Drug guide recommends 3-5mg/kg/day

administer orally in 2 divided doses.

Is the dose safe?

Supply

• Pediatric medication is typically supplied in liquid form

• Some children can swallow pills or the medication may only come in tablet form

• Most of the dosage assessment questions will consist of medication in liquid form, few questions will be in tablet form

Remember….

• Supply is expressed as a dosage amount per a commonly used quantity

• Example 250mg/5mL

100mg/mL

50mcg/mL

• This is different from the total amount of drug dosage in the bottle

Calculate Liquid Medication

Dose desired

Dose on hand X quantity in mL

= volume to be administered

Lets try it!

5. MD order is to give 75 mg

Supply is 250mg/5mL

Calculate the amount to administer

Read a label

• Some dosage questions will require you to read a drug label

Mixing directions:Add 30 mL of water

Mix VigorouslyDiscard after 5 days

Zantac

(ranitidine)

Oral suspension25mg/5mL

Lets try it!

6. Using the medication label supplied above, how many milliliters should be administered per dose if the MD order is 100 mg administer orally once daily?

Ok, so how do you round?Look at it this way…

– If the calculated answer is <1 mL then round to the hundredths place as this amount could be easily administered in a 1 mL syringe

Example: If the answer was 0.75 mL, where would you draw the solution to in this syringe?

What if the Answer is > 1 ml?

• If the calculated dose is greater than 1 ml then you round to the tenths place

• Example- if the dose was 2.75 ml, using a 3 ml syringe you would need to round to 2.8ml, as 2.75ml can not be precisely administered

For Example

• If the answer is 0.3762901

• Round to 0.38mL…..don’t forget the zero in the ones place!

• If the answer is 1.3762901

• Round to 1.4 mL

NEVER…….

• Round to a whole number!!!!!

• If the answer is 1.89361

• Round to 1.9 mL NOT 2 mL

So Remember:

• < 1 mL rounds to 2 places to the right of the decimal place

• >1 mL, kg, mg, mcg, anything else rounds to only 1 place to the right of the decimal place

Practice Rounding

• If you calculated the answer to be:

a.2.76001 mg, round to:__________

b.0.609113 mL , round to:_________

c.8.92778 mL, round to:__________

d.0.78912, round to:__________

e.13.119542 kg, round to:_______

Intravenous

• Nothing new here….

Volume in mL x drop factor = gtt/min

Time in min

You are Ready!!! Lets put it all together

8. The physician orders Kantrex (kanamycin) oral suspension 150 mg/kg/day administer orally in 2 divided doses.

Supply Kantrex 500mg/5mL.

Patients weight: 28 lbs

How many milliliters should be administered per dose?

9. The physician orders Prostigmin (neostigmine bromide) 8 mg administer orally every 4 hrs

The drug guide recommended dosage is 2-4 mg/kg/day to be administered in divided doses

Patients weight: 21 lbs

Is the physicians order safe?

Careful…some may have patients weight in kg already!

10. The physician orders Primacor (milrinone lactate) 50 mcg administer IM stat.

Supply: 0.2mg/mL

Patients weight: 12 kg.

How many milliliters should be administered per dose?

11. The physician orders Sustiva (efavirenz) 20mg/kg administer orally twice dailySupply: Sustiva 50 mg tablets

Patients weight: 11 lbs

How many tablets are to be administered per dose?

12. The physician orders IV fluids as follows: Infuse 1000mL of 0. 45% normal saline solution in 10 hours IV.

• Calculate the flow rate when the drop factor is 10 drops per milliliters

You are ready to take the practice test! Time yourself…you need to be

able to complete in 30 minutes