1. Pediatric and Adult Dosages Based on Body Weight
Chapter 13
Pediatric and Adult Dosages Based on
Body Weight

2. Caution
Those who administer drugs to patients are legally responsible for recognizing incorrect and unsafe dosages and for alerting the prescribing practitioner.
The one who administers the medication is just as responsible for the patients safety as the one who prescribes it!!
For the safety of the patient and yourself it is necessary that you familiarize yourself with the recommended dosages of drugs and consult a reputable drug reference. (package insert) or Hospital formulary

3. Adult Dosages Determined by drug manufacturer
Based on average weight of an adult
Minimum and maximum safe levels given
Very important that you read the drug labels and/or package inserts to familiarize yourself with average adult doses

4. Administering Medications to Children
Birth to 1 year of age have greater percentage of body water
Age 1 to 12 years metabolize drugs more readily than adults
Adolescents years
--this gives the child a decreased ability to absorb water soluble drugs, necessitating dosages of oral and some parenteral drugs that are proportionally higher than do those given to persons of larger size.
Metabolizing drugs quickly means a higher dosage required
ORGAN SYSTEMS still maturing
Adolescents erroneously thought of as adults due to body size (>50 kg) can still be physiologically immature due to hormonal changes and growth spurts

5. Administering Medications to Children
Children at risk for overdose, toxic reactions, and death
Due to immature physiological processes
E.g., absorption, distribution, metabolism, excretion
Need to be clinically monitored for response
MUST use a reputable drug source!
Infants and children must be frequently evaluated for response to medications given (serum drug levels, clinical response)

6. Administering Medications to Children
Safe pediatric dosages calculated by:
Body weight
Measured in mg per kg, mcg per kg
Body surface area (BSA)
Measured in m2
child’s weight always documented as kg
BSA uses height and is mostly used in oncology and critical care situations ie, Burn Units

7. Remember Approximate Equivalents *
1 kg = 2.2 lb
When converting pounds to kilograms, round kilogram weight to one decimal place
Tenths
1 lb = 16 oz
Have class convert 45 pounds to kg

8. Example One Convert 45 lb to kilograms Approximate equivalent
Equivalent is: 1 kg = 2.2 lb
Set up ratio
Have students work it out ENTRANCE FOR RATIO

9. Example One
Calculate
Cross-multiply
Simplify

10. Example Two Convert 10 lb 12 oz to kilograms Approximate equivalent
1 kg = 2.2 lb
1 lb = 16 oz
Set up ratio to convert ounces to pounds
Remember rules for converting

11. Ounces to Pounds
ENTRANCE: Answer: 10 lb 12 oz = lb
Answer: 10 ¾ lb

12. Example Two Convert 10 lb to kilograms
Change to decimal converting to metric system
Set up ratio and calculate
Have students calculate lb’s to kg’s ENTRANCE SLIDE FOR DECIMAL ANSWER
Ask for answer before changing slides
Have class set up ratio of # to kg before changing slides

13. Example Two
Calculate

14. Calculating Safe Pediatric Dosage: Body Weight Method
Steps:
Convert child’s weight in pounds to kilograms rounded to nearest tenth
2. Calculate safe dose as noted in drug reference by multiplying mg per kg or mcg per kg child’s weight in kg, rounding to nearest tenth
Most common method of prescribing and administering meds for a child is to calculate the amount of the drug according to the child’s body weight in kilograms.

15. Calculating Safe Pediatric Dosage: Body Weight Method
Compare ordered dose with recommended dose
Determine safety
If safe, calculate ordered dose and administer
If unsafe, consult prescriber
3. From a reputable drug resource

16. Calculating and Verifying Safe Dosages
Single dose example:
Intended to be given once or prn
Indicate a minimum and maximum range
aka “SAFE DOSAGE RANGE”
Physician orders morphine sulfate 1.8 mg IM stat
Child weighs 79 lb
Is the dose safe?
SINGLE DOSE DRUGS are intended to be given once or p.r.n.
HAVE CLASS convert lb to kg

17. Calculating and Verifying Safe Dosages
Convert 79 lb to kilograms
Approximate equivalent
1 kg = 2.2 lb
Set up ratio and calculate
Round to nearest tenth
How will we determine a safe dosage?

18. Calculating and Verifying Safe Dosages
Calculate safe dose in mg per kg as noted in reputable drug resource
Resource notes usual IM dose as 0.05 mg per kg per dose
Set up ratio and calculate

19. Calculating and Verifying Safe Dosages
Compare ordered with recommended dose
Ordered dose:
1.8 mg
Recommended dose:
Conclude ordered dose is safe
ask class what are other considerations in giving a narcotic to a patient?
Page 396: ask class which med they would pick out. Ask what the schedule is of Morphine THEN shut book!

20. Calculating and Verifying Safe Dosages
Calculate one dose
Ordered: Morphine sulfate 1.8 mg IM
Available: Morphine sulfate 5 mg per mL
Three step method…convert? Think? Calculate…

21. Calculating and Verifying Safe Dosages
Calculate one dose
Convert
No conversion necessary
Think
If 5 mg per mL and need 1.8 mg, will give less than mL
Note: Morphine is a Schedule II controlled substance, so you will retrieve it from the double-locked medication cabinet.
Co sign waste
Have students calculate

22. Calculating and Verifying Safe Dosages
Calculate one dose
Calculate
ENTRANCE:
WHAT syringe would you choose??

23. Calculating and Verifying Safe Dosages
Draw up 0.36 mL of morphine sulfate 5 mg per mL in 1 mL syringe
CAUTION: Remember that morphine is a controlled substance. You cannot just discard what is left over. Because all of the solution has to be accounted for, ask another nurse to witness you wasting the remainder according to agency policy and cosign the record.
ENTRANCE answer for amount of mL and syringe

24. Calculating and Verifying Safe Dosages
Single dosage range example:
Physician orders Vistaril 20 mg IM q. 4 h p.r.n. nausea
Child weighs 44 lb
Is the dose safe?
Have class calculate lb to kg

25. Calculating and Verifying Safe Dosages
Convert 44 lb to kilograms
Approximate equivalent
1 kg = 2.2 lb
Set up ratio and calculate
Round to nearest tenth
ENTRANCE FOR lb to kg

26. Calculating and Verifying Safe Dosages
Calculate safe dose in mg per kg as noted in reputable drug resource
Resource notes usual IM dose as 0.5 mg to 1 mg per kg per dose
Need to calculate minimum and maximum dosage range
Write 0.5 mg to 1 mg / kg/ dose on board
Set up calculation for both ranges

27. Calculating and Verifying Safe Dosages
Set up ratios and calculate minimum and maximum safe ranges
Recommended range is 10 to 20 mg per dose
ENTRANCE minimum, maximum, and rec range

28. Calculating and Verifying Safe Dosages
Compare ordered dose with recommended dose
Ordered dose:
20 mg
Recommended dose range:
10 to 20 mg
Conclude ordered dose is safe

29. Calculating and Verifying Safe Dosages
Calculate one dose
Ordered: Vistaril 20 mg IM
Available: Vistaril 50 mg per mL
Use three step method…

30. Calculating and Verifying Safe Dosages
Calculate one dose
Convert
No conversion necessary
Think
If 50 mg per mL and need 20 mg, will give less than 1 mL
Have students calculate

31. Calculating and Verifying Safe Dosages
Calculate one dose
Calculate
ENTRANCE for calculation
WHAT syringe will you choose?

32. Calculating and Verifying Safe Dosages
Draw up 0.4 mL of Vistaril 50 mg per mL in
1 mL syringe

33. To verify safe Peds dose by weight:
RULES and REVIEW:
Convert weight from pounds to kilograms (rounded to tenths)
Calculate safe dosage in mg/kg or mcg/kg (rounded to tenths) multiply mg/kg by child’s weight in kg
Compare the ordered dosage to the recommended dosage, decide if its safe
If safe, calculate amount to give and administer
IF dosage seems unsafe, what will you do?

34. Routine or Round-the-Clock Drugs
Total daily dose example:
Safe amount must be calculated, divided by number of doses per day, and compared with order
Physician orders amoxicillin 200 mg p.o. q. 8 h
Child weighs 22 lb
Is the dose safe?
Routine or “round the clock” drugs are intended to produce a continuous effect on the body over 24 hours.
They are recommended as a total daily dosage
WRITE AMOXACILLIN 200 MG PO Q 8 h on board
How many doses in a 24 hour period for q 8 hours?
Ask class: what do you need to do first? Convert to kg…have class convert first

35. Calculating and Verifying Safe Dosages
Convert 22 lb to kilograms
Approximate equivalent
1 kg = 2.2 lb
Set up ratio and calculate
ENTRANCE: lb to kg
Turn to page 403, figure 13-4
Look and tell me what’s important there: dosing for kids with frequency; storage instructions;

36. Calculating and Verifying Safe Dosages
Calculate recommended dosage
Recommended dose detailed on drug label:
20 to 40 mg per kg per day in divided doses
Label further recommends that total daily dosage be divided and administered every eight hours
Resulting in three doses in 24 hours
Note that ordered dose is for every eight hours
Have class calculate min and max total daily doses and then, min and max single doses every 8 hours

37. Calculating and Verifying Safe Dosages
Calculate minimum and maximum daily dosage and single dose:
ENTRANCE for ALL doses.
Example is broken down on page 403 for review

38. Calculating and Verifying Safe Dosages
Compare ordered dose with recommended dose
Ordered dose:
200 mg per dose
600 mg per day
Recommended dose range:
66.7 to mg per dose
200 to 400 mg per day
Ask class if ordered dose is a SAFE dose…

39. Calculating and Verifying Safe Dosages
Compare ordered with recommended dose
Conclude ordered dose is not safe
Too high
Contact physician to discuss order
Also, a pt can be UNDERDOSED too!
Do example from page 414, #9
Can also do example # if time permits

40. Calculating and Verifying Safe Dosages
Combination drugs example:
Combination drugs
Two separate drugs combined into one pill, solution, suspension.
Ordered as a dose volume of concentration to give
When calculating safe dosage for combination drugs:
Calculate safe dosage for each drug in the combination
Compare with ordered dose of each
Page 407 shows 2 examples of these medication types
Be aware that OTC meds for kids still use household measurements based on pounds, but always convert to kg in hospital settings

41. Combination Drugs
PAGE 408 (for me)
Child’s weight is 22 pounds. Have class convert to kg (10) kg
For moderate infections the usual IV or oral dosage is 6-12 mg TMP/kg/day divided q 12 h
Convert pounds to kg
Calculate safe dosage for the TMP range (min and max)
Calculate volume of med for dosage range (min and max dose volume)
Decide if dose volume is safe
Give co-trimoxazole 40/200 suspension 7.5 mL p.o. Q 12 h

42. Combination Drugs
Page 409,410 for me
Explain that this is the normal dosage amount per resource for a child Calculate the max daily dose of Acetaminophen
Weight is 42 lb
Convert weight to kg
Calculate safe dosage range for codeine (min and max)
Calculate dose volume of medication for the min and max dosage
Decide if dose volume is safe (YES)
Give tylenol and codeine suspension 7.5 mL (acetaminophen 120mg with codeine 12 mg/5 mL) p.o. stat and then Q 4 h p.r.n. pain

43. Calculating and Verifying Safe Adult Dosage: Body Weight Method
Many drugs prescribed for adults are also dosed based on body weight
Use same process and rules as calculations for safe pediatric dosages

44. Caution
Once adolescent attains weight of 50 kg (110 lb) or greater, standard adult dosage frequently prescribed
Verify that order for child’s dosage does not exceed maximum
Ask class to state the 4 steps of calculating pediatric doses

45. Steps for calculating pediatric dosages:
Convert pounds to kg rounding to tenths
2. Calculate safe dose by multiplying mg/kg; checking with reference guide
Compare ordered dose with recommended dose
If safe, calculate ordered dose and administer
ENTRANCE for all
Practice: REVIEW SET to start

46. Homework: 1-24 ALL problems

47. Chapter 13 quiz next week