Newman: Dosing Flashcards
Why is there no standard dose for most pet meds
Grow and develop quickly. Metabolic and clearance pathways begin in fetus and continue throughout childhood. Changes that occur as we grow:
- Absorption
- Distribution
- Metabolism
- Elimination
How does absorption change as children grow?
- Composition of intestinal fluids and the permeability of the gut both change
- Gastric pH is higher in neonates than children and adults (affects absorption of oral frugs)
- Neonates, infants and children absorb more through skin bc larger surface area/volume ration and thinner stratum corneum
Caution with topical meds in children
Can be absorbed in toxic doses (topical diphenhydramine; Benadryl)
How does distribution change as children grow?
Stores of fat and water change
Neonates/infant = high extracellular water
Fat stores increase
Alter 1/2 life of drug = adjust dose
How does metabolism change as children grow?
Enzyme activity increase: mature levels and activity is reached by 2YO
How does elimination change as children grow?
- Preterm neonates develop renal excretion paths more slowly.
- GFR reaches adult levels by 2YO
Ped doses are usually given in
- mg/kg/day
2. mg/kg/dose
Trusted sources that list recommended doses
- Tarascon Pharmacopoeia
- UpToDate
- Harriet Land Handbook (Johns Hopkins)
Convert pounds => kg
divide by 2.2
Conver kg => pounds
x 2.2
calculate dose:
2YO 22lbs pt needs amoxicillin. Recommended dose = 80-90mg/kg/day in 2-3 doses
22 lbs => 10 kg
90 * 10 = 900mg/day
Divide by 2 doses = 450mg BID
How to write prescription for last pt
Amoxicillin (400mg/5mL)
Dispense: 110 mL
Sig: 440mg (po) BID x 10day
Is rounding up or down to the nearest mL or tablet size okay?
For ABX = okay
Digoxin = not okay.
When writing paper/electronic prescriptions for peds, what should you include?
- Pt weight
- Concentration (suspension of solution) or size of tablet/capsule (mg)
- Write med in mg, NOT volume or # of pills.
Why and when are meds dosed according to body surface area (BSA)?
- Takes into consideration variability of pts size and ABNL adipose tissue.
- Links dosing to how mature organs are and metabolic rate, compared to weight
- Used for drugs w high toxicity (chemo)
Explain why you should not exceed the “maximum adult recommended dose” or the “maximum dose for large children” when prescribing medicine to pediatric patients.
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”
Explain why you should not exceed the “maximum adult recommended dose” or the “maximum dose for large children” when prescribing medicine to pediatric patients.
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:
- Affects the distribution of hydrophilic meds/lipophillic meds (distributed widely)
- Affects liver metabolism
How can you reduce potential for medication errors when writing prescriptions?
- Write clear and concise
- Differentiate between mg/kg/day and mg/kg/dose
- Include patients weights so pharmacist can check
- Never put a decimal point after whole number (do NOT write 4.0mg)
- ALWAYS place a 0 in front of a decimal point (write 0.2mg)
- Order meds in mg, NOT mL.
- If once daily, write “once daily/ q24hrs), NOT qD.
- Do not abbreviate drug names
- Write micrograms as (micrograms*** OR mcg), NOT ug
