peds Flashcards
What are key concepts in peds PK and PD
there is little info on PK&PD 2/2
variations in absorption of meds from GI, IM injection sites and skin, and premature and other newborn infants
they are NOT just little adults!
ADME varies between kids and adults, and kids and kids
Concomitant diseases can influence dosage and requirements to achieve a targeted effect
Weight based dosing for obese kids can lead to subtherapeutic doses
What are the peds age ranges
Premature: infant born <37 weeks Neonate: birth-1 month Infant: 1 month- 1 year Children: 1-11 years Adolescents: 12--16 Peds: <18 *Can start dosing kids as adults at 16
Are a lot of drugs used in peds
yes, most marketed drugs can be used for peds pts
but 1/4 have indications for specific use in peds
ADME is different between neonates, premature, children, and adolescents
What affects absorption from GI tract
pH dependent passive diffusion
gastric emptying time
What is gastric pH at birth
ranges from 6-8!
within 24 hours it decreases to 1-3
-in premature kids, pH stays high because of immature acid secretion
What happens in GI of premature infants
higher gastric pH= higher concentration of acid labile drugs (penicillins) and lower of weak acids (phenobarbital)
Passive and active transport may be fully developed by 4 months old
*Gastric emptying is slow
What factors affect IM absorption in premature infants
relative muscle mass poor perfusion to various muscles peripheral vasomotor instability insufficient muscular contractions -can't predict the net effect of these factors on drug absorption
What happens to skin absorption in peds
percutaneous absorption increased (underdeveloped epidermal barrier, increased skin hydration)
increased absorption of steroids
total body surface area:total body weight is highest in younger
What is drug distribution determined by in peds
Physicochemical properties of the drug (molecular weight, PKa)
Physiologic factors specific to the pt (total body water, protein binding, pathologic conditions)
What happens to total body water with age
fetus: 94%
premie: 85%
full term: 78%
adults: 60%
-gentamicin distribution volumes of 0.48 l/kg in neonates, and 0.2 l/kg in adults
EC fluid volume accounts for
50% body weight in premies
35% body weight in 4-6 mo. old
25% in kids 1 yr
19% in adults
What happens to distribution in newborns
decreased! 2/2
decreased plasma protein concentration, lower binding capacity of protein, decreased affinity of proteins for drug binding, competition for certain binding sites by endogenous compounds (like bili)
What about premies and distribution
May require larger loading dose than older kids to get to therapeutic concentration (ex. phenobarbital, phenytoin)
What happens to free drug in peds bodies
increased concentration of free drug (unbound)
Drugs bound to plasma proteins can not be eliminated by kidney
increase in free drug may also increase clearance
What happens to distribution based on body fat
body fat is lower, so highly lipid soluble drugs are distributed less widely in infants
What happens to metabolism in peds
It is much lower in infants than older kids bc while sulfation path is well developed, Glucuronidation pathway is underdeveloped!
ex: APAP is metabolized through the glucuronidation path, so they compensate by trying to metablize thru sulfation pathway
What is grey baby syndrome
decreased metabolism of chloramphenicol by Glucu pathway causes build up of chlormaphenicol
Morphine and infants
May need higher serum concentration of morphine to achieve efficacy
infants can NOT metabolize morphine to it’s active 6-Glucuronide metabolite
What other drug oxidation is impaired in peds
theophylline, phenobarbital, phenytoin
What happens to GFR in peds
may be as low as 0.6-0.8 in premies, and is appx 2-4 in term infants
Processes may not fully dvelopuntil weeks-1 yr after birth
What are concerns about common cold remedies in beds
serious toxicities associated with antihistamines, decongestants, antitussives, and expectorants
FDA says do NOT use in <2 y/o, companies label not for use <4!
What is the concern with benzyl alcohol use in peds
Causes syndrome of:
metabolic acidosis, seizures, neurologic deterioration, gasping respirations, hepatic and renal abn, CV collapse, death
-it is a preservative used in IV flush solutions, IV DXM, methylprednisone, enoxaparin, midazolam, and multivitamins
What is the concern with tetracyclines
contraindicated in pregnant women, nursing mothers, and kids <8 because:
cause dental staining and defects in enamelization of deciduous and permanent teeth
Decrease in bone growth
What are concerns with fluoroquinolones
Not recommended for peds or pregnant women, may cause cartilage leisons and arthropathy; *tendonitis and rupture in all ages
EXCEPT if:
<18 w/ inhalation anthrax
Tx complicated UTI and pyelo caused by E Coli
peds w/ CF
What are concerns with antidepressants
May increase risk of suicide in younger pts
Approved: Sluoxetine, Sertraline, Fluvoxamine
Always assess risk vs benefit; they have a BLACK BOX WARNING!
How do you determine dose in peds
MC and reliable method: Body weight!
Least reliable: Age!
most accurate: body surface area
(formulas rely on weight, age, body surface area, and mg per weight per day)
What is Clark’s rule (weight)
(kids weight in lb / 150) x adult dose = child’s dose
What is Fried’s rule (age; for very young)
(age in mo./150) x adult dose = child’s dose
What is Young’s rule (age)
(age in yr/age +12 yrs) x adult dose = child’s dose
*ONLY for kids 1-12
What is a nomogram
a chart that takes into account height and weight to calculate BSA
Dosage for BSA is un units per M2*
What is the MC way in which doses are expressed
units per Kg
But this means you have to know patient’ weight! include on every Rx you write so the pharmacist can verify the dose
MUST specify per DAY or per DOSE
*always include indication on the label! (ex: for ear infection)
Know these conversions
1 teaspoon: 5 ML
1 tablespoon: 15 ML
1ounce: 30 ML
1 cup (8oz): 240 ML
What are ways to prevent calculation errors
Bracketing: write out “pt weights 20kg. 20kg x 8mg/kg/day = 160mg”
Ask colleague or staff
phone a pharmacist
*NEVER memorize peds doses… look them up!
Are organ systems normal in kids
no, they are not fully developed!
absorption may take longer, fat soluble drugs may take longer to distribute, may have slower or more rapid metabolism
Kids have slower excretion rates= more likely toxicities
How do you admin dropper meds to kids
on the cheek, not the back of the tongue
