Medicines for children Flashcards
Terminology
- Pre-term or premature = born <37 weeks
- 0-27 days= neonate
- 28-23 months= infant/toddler
- 2-11 years= child
- 12-16/18= adolescent
- Gestational age= conception to birth
- Post conceptional age= Gest age +No. weeks since birth
First 18 months
Movement -0-3 months lift head -6-8 months sit -10-18months walk alone -3months+ handling -8moths= one hand to another -12 months= start feeding themself Hearing and talking -Cooing 6 months -first word = 12 months Sight -Recognise parents in 2weeks -See in 6 months
Consideration of medicines in children
- THEY ARE NOT SMALL ADULTS
- Large varied population
- Significant pharmacokinetic (ADME) and pharmacodynamic differences between child age bands and with adults
Pharmacokinetic differences absorption (orally)
-GI tract changes
-NEONATE pH increased (6-8)
+ Decreased bioavailability of acidic medicines (phenobarbital, phenytoin) NB we need drugs in unionised forms
+Increase bioavavailability of weakly basic drugs (penicilins, erythromycin)
-Gastric emptying and intestinal motility decreased in neonates
+This leads to unpredictable absorption
+Normal function by 4-6months
Pharmacokinetic difference absorption -
IM and PR
-I.M injection \+painful and distressing for children \+Rate and extent of absorption depends upon blood flow to the muscle (dependant on muscle mass, increased muscle mass= increased blood flow= increased absorption) hence neonate will be slower -PR (rectal) \+May be slow and unpredictable \+Not nice \+Useful if vomiting or NMB or emergency \+Useful in seizures when oral and IV routes cannot be done
Pharmacokinetic difference absorption -
Percutaneous and Intraosseous (IO)
-Percutaneous
+Absorption significantly greater than in adults due to
1)Neonates have thinner stratum corneum (thinner skin)
2)Increase SA:weight ration
-Intraosseous (IO)
+Injection into bone
+(usually tibia)
+similar bioavailability to IV
+Use in kids up to 6 (bones are soft enough to do it)
Pharmacokinetic difference absorption - IV
-Guaranteed method of drug delivery (100% bioavavailability)
-Preferable in neonatal period
+Clinical condition
+Prematurity- no mature liver or kidney to metabolise
+Gastric instability- no full absorption GI tract
-Caution with rate of infusion and fluid volumes as different size to an adult
+Term neonates should receive 60-150ml/Kg/day of fluid
+Average 3 year old (15kg) 1250ml/day
Volume distribution
-Water= high in the foetus and slowly reduces to 60% in children
-Body fat= low in premature babies (2%); High in children up to 1 yr old (30%)- reduce back to adult value (18%)
-The distribution indicates where soluble drugs can do distributed
NB- is this significant to drug therapy?
YES- have to take into account water soluble drugs (gentamicin) and fat soluble drugs
-Gentamicin used for neonatal sepsis, in premature babies the gentamicin will distribute evenly through the water soluble space (98%) this will lower conc therefore dose needs to be riased NB for fat soluble its the other way therefore have to reduce conc
Protein bindind
- Protein binding altered in neonates and young children; gets reduced
- Potentially more free drug available to hit receptor sites
- Therefore, need to reduce doses of highly protein bound drugs e.g. phenytoin, sodium valporate and furosemide
- This increased conc of drug can lead to more side effects and can even go into toxicity
- Other factors effecting drug distributio : organ perfusion and blood flow
Pharmacokinetic differences metabolic/Excretion
-Neonatal liver immature for metabolism of drugs
+Why you see grey babies (IV-chloramphenicol no metabolism of drugs)
-Renal clearance can take 8-12 months to develop to adult values
-Can get longer half lives and higher plasma conc of heptatic and renally excreted drugs
1)Phenytoin- 75hr half life in neonate; 20hrs through neonatal period; once 2 weeks= 8hours- maturing of liver and kidney
2)Analgesics
3)Cardiac glycosides (digoxin- v.toxic)
Pharmacodynamic effects
-Interaction between drug and receptor
-Less known
-May explain increased hepatic toxicity seen in infants on sodium valporate
+With sodium valporate there is an increased half life- drug is cleared slower-> more build up of drug leading to higher plasma conc = more side effects
Difference in monitoring: respiratory rate
1) Infants= 30-40/min
2) Toddler= 24-40/min
3) School age= 18-30/Min
4) Adolescent= 12-16/min
Difference in monitoring: Heart rate
1)<3 months mean 140
2)3mth-2yr mean= 130
3)2yr-10yr mean=80
4)>10yr mean=75
NB awake if more than sleep
Difference in monitoring;
BP
1)Day 1 (<1kg) 39-59/16-36
2)Day 1 (3Kg) 50-70/25-45
3)Neonate= 60-90/20-60
4)Infant= 87-105/53-66
5)Toddler= 95-105/53-66
6)>7yrs= 97-122/57-71
7)>15yrs= 112-128/ 66-80
NB- dont need to remember exact values
Other differences in monitoring
-Haematological changes
+Hb and neutrophils lower in younger children
+Lymphocytes higher mean in younger children
+Platelets decreased in first few months, normalised by 6 months
NB labs have own standard values so important to use these
