Newman: Dosing

Question 1

Why is there no standard dose for most pet meds

Answer 1

Grow and develop quickly. Metabolic and clearance pathways begin in fetus and continue throughout childhood. Changes that occur as we grow:

1. Absorption
2. Distribution
3. Metabolism
4. Elimination

Question 2

How does absorption change as children grow?

Answer 2

1. Composition of intestinal fluids and the permeability of the gut both change
2. Gastric pH is higher in neonates than children and adults (affects absorption of oral frugs)
3. Neonates, infants and children absorb more through skin bc larger surface area/volume ration and thinner stratum corneum

Question 3

Caution with topical meds in children

Answer 3

Can be absorbed in toxic doses (topical diphenhydramine; Benadryl)

Question 4

How does distribution change as children grow?

Answer 4

Stores of fat and water change

Neonates/infant = high extracellular water
Fat stores increase

Alter 1/2 life of drug = adjust dose

Question 5

How does metabolism change as children grow?

Answer 5

Enzyme activity increase: mature levels and activity is reached by 2YO

Question 6

How does elimination change as children grow?

Answer 6

• Preterm neonates develop renal excretion paths more slowly.
• GFR reaches adult levels by 2YO

Question 7

Ped doses are usually given in

Answer 7

1. mg/kg/day

2. mg/kg/dose

Question 8

Trusted sources that list recommended doses

Answer 8

1. Tarascon Pharmacopoeia
2. UpToDate
3. Harriet Land Handbook (Johns Hopkins)

Question 9

Convert pounds => kg

Answer 9

divide by 2.2

Question 10

Conver kg => pounds

Answer 10

x 2.2

Question 11

calculate dose:

2YO 22lbs pt needs amoxicillin. Recommended dose = 80-90mg/kg/day in 2-3 doses

Answer 11

22 lbs => 10 kg

90 * 10 = 900mg/day

Divide by 2 doses = 450mg BID

Question 12

How to write prescription for last pt

Answer 12

Amoxicillin (400mg/5mL)
Dispense: 110 mL
Sig: 440mg (po) BID x 10day

Question 13

Is rounding up or down to the nearest mL or tablet size okay?

Answer 13

For ABX = okay

Digoxin = not okay.

Question 14

When writing paper/electronic prescriptions for peds, what should you include?

Answer 14

1. Pt weight
2. Concentration (suspension of solution) or size of tablet/capsule (mg)
3. Write med in mg, NOT volume or # of pills.

Question 15

Why and when are meds dosed according to body surface area (BSA)?

Answer 15

1. Takes into consideration variability of pts size and ABNL adipose tissue.
2. Links dosing to how mature organs are and metabolic rate, compared to weight
   - Used for drugs w high toxicity (chemo)

Question 16

Explain why you should not exceed the “maximum adult recommended dose” or the “maximum dose for large children” when prescribing medicine to pediatric patients.

Answer 16

If the calculated dose is more than the adult dose, do some research to see what is considered the maximum mg/kg/day dose. Use adult dose as “top limit”

Question 17

Explain why you should not exceed the “maximum adult recommended dose” or the “maximum dose for large children” when prescribing medicine to pediatric patients.

Answer 17

If the calculated dose > adult dose = do some research to see what is considered the maximum mg/kg/day dose => Use adult dose as “top limit”.

Weight-based dosing (mg/kg) of medications is a problem in these fat kids bc increased weight:

1. Affects the distribution of hydrophilic meds/lipophillic meds (distributed widely)
2. Affects liver metabolism

Question 18

How can you reduce potential for medication errors when writing prescriptions?

Answer 18

1. Write clear and concise
2. Differentiate between mg/kg/day and mg/kg/dose
3. Include patients weights so pharmacist can check
4. Never put a decimal point after whole number (do NOT write 4.0mg)
5. ALWAYS place a 0 in front of a decimal point (write 0.2mg)
6. Order meds in mg, NOT mL.
7. If once daily, write “once daily/ q24hrs), NOT qD.
8. Do not abbreviate drug names
9. Write micrograms as (micrograms*** OR mcg), NOT ug