Day 3: Dr. Peterson Flashcards
What is the length for a full term prego and at what week will they try to revive the baby if it must be born?
Full term is 40 weeks
At 23 weeks they will try to revive the baby if born
**A 20 week baby will weight around 400g
What are the pediatric dosing options?
Age-based dosing
Body weight- based
Body surface area- bases
What are the pros and cons of age-based dosing?
Pro
It’s practical
Easy to use (parents can just quickly see how much to give child based on age no math needed)
Cons:
Assumes that maturational effects on drug disposition is conistent across the age category (EX: a child who is 1 is grouped in the same as a 3)
This is a con because there can be large PK differences between a 1 and 3 year old.
What are the stages and age/definition for development?
Fetus: > 8 weeks in womb
Neonate: birth to 4 weeks
Premature < 37 weeks gestation
Infant: 4 weeks to a year
Child: 1 to 12 years
Adolescent: 12 to 18 years
What are the pros and cons of weight based dosing?
Pros:
Practical
Easy to assess (what’s used most often)
Cons:
Does not account for PK of age
Underweight pets can be underdosed, while over weight pets can be overdosed
What are the pros and cons of body surface area-based dosing?
Pros: Gold standard
More accurate than weight based for pets
Decreases risk of over-dosing in older children
Cons:
Difficult to calculate
Many different formulas for BSA and it might give different answers
Can over dose neonates
What is the equation for BSA?
Sqrrt ((Height (cm) x weight (kg)) / 3600
What is the number one problem with oral route for ped patients?
The drugs taste badly so the children do not want to eat it
How does the pH of a peds stomach affect absorption?
At birth the pH of the stomach is neutral (not much acid in stomach)
The pH will drop over 2 years until it reaches adult values
While the stomach is not a primary site of absorption for most drugs it affects their stability.
EX: A drug like B-lactams and macrolides are acid labile (meaning that acid will break them down). As an adult when the drug hits the stomach we break it down which means less drug is available to be absorbed. For a baby when it hits the stomach they don’t break it down meaning that MORE drug is available to be absorbed. Need to lower doses for these drugs
What are the differences in gastric emptying for ped patients?
You get delayed gastric emptying = reduced motility and peristalsis.
This means that even after they take the drug it will sit in their stomach and not go to where it should be absorbed
Some drugs can increase the time and allow for better absorption
Can you still give oral drugs to ped patients?
Yes, even tho they have differences the overall oral BA of drugs in adequate and they can be given
Can you use Muscular route for neonates?
Yes, we give vaccines this way but it does have its problems for drugs
It’s unreliable because blood flow varies over the first 2-3 weeks of life and this causes unpredictable systemic absorption
Can you use rectal route for absorption in peds patients?
Not very good for neonates and young children
In kids the rectum is alkaline while adults are more neutral
Also propagation (lots of pooping) of lower GI in infants (if they are always going to the bathroom and cant control themselves the drug will be expelled out)
**only really used if oral route can not be done
What is important to note about topical absorption in neonates?
They have faster and higher systemic concentrations than adults
Reasons why:
Very thin skin
Poorly keratinised
Well-hydrated stratum corneum
Large surface area
***watch application of lidocaine and corticosteroids
What can happen from topical terroir toxicity?
thinning of the skin
Glucose abnormalities (inc blood glucose)
Immunosuppressive
Adrenal crisis (HPA axis toxicity)
Hypothalamus —> Pituitary—> adrenal gland —-> Cortisol (then negative feedback to hypothalamus
What is different about the metabolism in neonates and children?
Their hepatic blood flow (therefore the liver’s ability to metabolize meds) is decreased at birth
The hepatic enzymes are also immature the first year of life (CYPS)
**how can test liver function? You can do ALT/AST but that only shows dmged liver cells, there for you can run INR which can be a marker for the cofactors needed in the clotting cascade
How is the rectal route in terms of metabolism for children and neonates?
You have to watch where you insert it, since they have anatomical differences if you place it in the wrong spot you can get a lot fo first pass metabolism
How is distribution in neonates and children different?
When you are born you have a much higher fraction of total body water
This will cause hydrophilic drugs to have a larger distribution and lower plasma concentration in neonates and young infants
In terms of body fat stores are limited in premature and newborn infants but it does not change the Vd
What is the difference in the fraction of unbound drug for neonates and infants vs children and adults?
Neonates and infants have MORE unbound drug
The reason is because their liver isn’t at full function so less albumin is produced (main protein that is binds drugs)
EX: a drug Ike phenytoin which has high protein binding will not be able to bind because there is less albumin so more free unbound drug is in the body. This means you need to lower the dose when given to the baby.
How does exertion of a neonate and new born differ from that of an adult?
Nephrogenesis do not begin until 9 weeks of gestation and is completed by 36 weeks
This means that preterm neonates will have a very low GFR but as you age it will increase
**wadult capacity is achieved in first 1-2 years of life
What is the process of breaking down a RBC?
RBC —> Heme —> Bilirubin —> bind to albumin—-> travels to the liver —-> gets conjugated —-> goes into bile —> to small intestine —> then into poop
Why does bilirubin cause a problem in neonates ?
A RBC in a baby is only 80 days so they have more breakdown also since they have poor liver function they have less albumin to carry it to the liver to excrete it. Also when it gets reabsorbed into the body it compounds the problem
***this is an issue because it will build up inside the neonate and cause them to have jaundice
Why do you put a child with jaundice into sun light?
You do this because phototherapy is an indirect way to cause conjugation of the bilirubin so it can be excreted
What are some medications that can cause Hyperbilirubinemia?
Sulfonamides (cant give to someone older than 30 days)
Contrast media
Bumetanide (loop diuretic)
Ceftriaxone (must be older than 30 days)
Ibuporfen (shouldn’t give to kids less than 6 months) it can displace bilirubin
What are the consequences of hyperbilirubinemia in peds?
Jaundice
Bilirubin encephalopathy - results in high concentration in blood and CNS (can lead to mental retardation)
Can also have neurologic sequelae
Cerebral palsy
Hearing loss
Gaze abnormalities, upward gaze
Dental enamel dysplasia
