Pediatric lecture Flashcards
What are the basic conversions needed for pediatric pharmacy practice?
always in metric system
* 2.2 lbs = 1 kg
* 1 teaspoon = 5 mL
* 1 tablespoon = 15 mL
* 1 inch = 2.54 cm
avg adult is 70 kg
Define gestational age (GA)
Time elasped between the first day of the last mestrual period and day of birth.
* full term is 38-40 weeks and 50% survival at 22 weeks
Define postnatal age (PNA)
Time elapsed from birth
Define postmentrual age (PMA)
Gestational age + postnatal age
* combination use for dosing
What is the importance of gestantional age?
Takes into consideration the development time in the womb.
* 1 day old baby can have different development depending on if full term vs. premature gestation
Define premature.
< 37 weeks gestation
Define term
> or = 37 weeks gestation
Define neonate
< 1 month old (28 days)
Define infant.
1-12 months old
Define child.
1 - 11 years old
Define adolescent
12 - 18 years old
Dose is primarily based on what?
Weight
Explain the pediatric calculation of a drug with a wide therapeutic range
mg/kg
When both age and weight are provided –> weight should be used
* generally okay to round by 5-10% (depending on the drug)
* ex. antibiotic
Explain the pediatric calculation of a drug with narrow theraputic range
mg/m^2 - body surface area
* ex. chemotherapy –> should not be rounded
Explain how medications beyond neonates are dosed.
Medications beyond neonates are generally dosed per day if scheduled or per dose if given as needed.
Explain dosing of neonates.
- use Neofax or neonatal reference
- dose can be based on PNA or a combination of PNA, GA, and PMA depending on the medication
- cannot extrapolate from pediatrics
A 25 lb child needs amoxicillin for her ear infection. It should be dosed at 90 mg/kg/day in 2 divided doses. Max adult dose is 2 g/dose.
- 25 lb/2.2 lb = 11.4 kg
- 11.4 kg x 90 mg/kg/day = 1026 mg/day
- 1026 mg/day / 2 doses/day = 513 mg/dose
Describe what should be done if older children or adolescents reach the max adult dose?
- Patients will reach the adult max dose around 20-35 kg
- Do not dose mg/kg past the max adult dose!
For amoxicillin, generally the max is 1000mg/dose, so for ear infections if given twice a day that would max at 2 grams per day. What weight would this max out at?
- 1000 mg/dose x 2 doses = 2000 mg
- 2000 mg / 90 mg/kg/day = 22.22 kg/day
What factors need to be considered for oral absorption in children?
- gastric pH
- intestinal motility
- rate of gastric emptying
Describe the gastric pH of neonates.
First few weeks of life –> less acidic (pH >4)
* premature neonates are unable to produce significant acid for first 1-2 weeks.
* pH is similar to adults by 2 years old
* adult pH ~ 0.9-1.5
Explain the absorption difference between a weakly acidic and weaky basic drug in neonate.
Weakly acidic drug
Drug is charged in the stomach –> cannot cross the lipid bilayer readily to be absorbed
Weakly basic drug
Drug is neutral in the stomach –> can cross the lipid bilayer readily to increase absorption
In neonate, there less weakly acidic drug absorbed and more weakly basic drug absorbed
Describe intestinal motility in pediatrics.
Variable in young infants and neonates
* difficult to predict the rate of absorption and extent of absorption
Compare gastric emptying of ped. patients and adults.
At birth and in premature neonates: prolonged gastric emptying
Around 4 months: similar gastric emptying
What factors influence gastric emptying time?
- gestational age
- food intake
- disease states
Describe absorption through the GI tract of neonate, infant, and children.
Describe the non-oral routes of administration.
IV
* optimal bc bioavailability = 1
* requires radiology to find small veins
IM
* painful –> sometimes necessary
* not much muscle mass to work with
transdermal
* not usually intentionally used –> often inadvertent use leading to toxicity
* not fully formed skin increases absorption
rectal
* dosage form issues
* depending on location, may worry about first pass mechanism
Describe the water/fat distribution in neonates and young infants.
Neonates and young infants have high total body water and extracellular water.
* babies are bags of water
* older infants have increased lipophilic distribution
fat composition:
12 month old - 23%
15 year old - 13%
Identify commonly used water-soluble medications.
In neonatal period meds increase mg/kg dosing vs. in older patients
- caffeine, gentamicin, indomethacin, linezolid, morphine, vancomycin
Neonates have increased free fraction of medications that are highly protein bound due to:
- decreased concentration, binding affinity, and binding capacity of plasma proteins
- similar to adults by 12 months old
Describe bilirubin.
The byproduct of RBC destruction
* requires conjugation in the liver
* eliminated via the stool
* binds to albumin
Neonates have:
* decreased GI motility
* decreased albumin affinity, concentration, and capacity
* increased permeability of BBB
Explain the effect of highly bound protein drugs on bilirubin in the body.
- Bilirubin binds to albumin.
- Drugs that bind highly to albumin can displace bilirubin.
- Bilirubin can penetrate the CNS bc of the unformed BBB –> deposits in the brain and causes brain damage
Explain the effect of highly bound protein drugs on bilirubin in the body.
- Bilirubin binds to albumin.
- Drugs that bind highly to albumin can displace bilirubin.
- Bilirubin can penetrate the CNS bc of the unformed BBB –> deposits in the brain and causes brain damage
Explain hepatic metabolism in neonates, infants, and preschool aged children.
They have increased relative size of liver –> increased metabolism of some medications.
After steady state, ____ provides more information than volume of distribution.
clearance!
Explain renal elimination in neonates.
GFR, tubular secretion, and tubular reabsorption are all decreased in neonates.
What is considered normal urine output?
Normal for children»_space; 1 mL/kg/hr
Explain the modified schwartz equation.
Helpful for pharmacists as MANY medications need dose adjustment for clearance calculations < 50-60 mL/min.
* values > 75 should be reported as such
* most accurate in the range of 15-75 mL/min/1.73m^2
Compare the half-life between neonates, children, and adults.
neonates > adults > children
neonates:
* half-life dependent on Vd and clearance
What is the KID List used for?
Medications that should be avoided or used in caution in at least some pediatric patients.
What are some formulation issues for ped patients?
- alcohol containing liquids
- sucrose content in liquids can worsen diabetic control
- phenylalanine in medications issue in patients with phenylketonuria
- carbohydrate content in meds for patients on ketogenic diet for seizures
- sorbitol contained in medications to prevent intestinal obstruction –> can lead to dehydration and electrolyte imbalance
Can sulfamethaxazole/trimethoprim (bactrim) be used in a 7 day old patient?
No. Sulfonamides are not used in patients < 28 days because of bilirubin build up –> brain damage.
