Paed - L1 Intro

Question 1

Paediatric categories - 6

Answer 1

Premature baby: Born before 37 weeks (we have babies up 23 weeks)
Term baby: Born at 37 – 42 weeks gestation.
Neonate: The first 28 days of life
Infant: Up to 2yrs
Child: From 2-12 yrs
Adolescent: From 12-18yrs

Question 2

Gestation & prematurity - 4

Answer 2

1. Gestation: time elapsed between first day of mum’s last period to estimated day of delivery. Normally 40 weeks. Premature if under 37 weeks.
2. Gestational age: neonate’s total age as weeks – allows for estimation of development in womb.
   Gestational correction should be continued until:
3. 1 year for infants born 32-36 weeks
4. 2 years for infants born before 32 weeks

Question 3

Complications of prematurity: Short-term complications - 7

Answer 3

1. Breathing difficulties due to immature & under-developed respiratory system
2. Heart problems e.g. patent ductus arteriosus & low BP
3. Bleeding in the brain
4. GI problems that can result in necrotizing enterocolitis (NEC).
5. Anemia & newborn jaundice
6. Hypoglycemia
7. Immune system problems – high risk of infection

Question 4

Complications of prematurity: Long-term complications – 5

Answer 4

1. Cerebral palsy
2. Impaired learning
3. Dental problems
4. Behavioral & psychological problems
5. Chronic health issues such as infections, asthma & feeding problems.

Question 5

PDA (Patent ductus arteriosus) – 4

Answer 5

1. The patent ductus arteriosus (PDA) is a blood vessel present in foetuses connecting the pulmonary artery to the aorta & allows oxygenated blood (from the placenta) to bypass the lungs, which aren’t used before birth. Normally, this vessel closes after birth when the baby starts breathing & the lungs take over oxygenation.
2. In some babies with congenital heart defects (e.g. hypoplastic left heart syndrome, left side underwhelmed) — PDA remains crucial for blood circulation, keeping blood flowing to the body, though oxygen levels may be lower.
3. If the PDA closes too early, especially undiagnosed heart defects, the baby can become unwell, showing signs like sweating, pallor, & difficulty feeding. In such cases, doctors use a prostaglandin analogue (e.g. alprostadil) to keep the PDA open until a surgical plan is in place.
4. Drugs like paracetamol & ibuprofen are prostaglandin antagonists—they can close the PDA, which is dangerous in these babies, causing cautions under 8 weeks, in case of undiagnosed heart defect.

Question 6

Paediatric prescribing- 3

Answer 6

1. Drugs prescribed in mg or g base, bar medicines which have [labelled]
2. Use current BNF
3. Never allow abbreviations to prevent errors e.g. FeS04 or Bruphen – prescriptions should be generic unless brand specific.

Methods of dosing:
Weight based: mg/kg basis – Consider underweight & overweight patients.
Age based
Body SA (BSA mg/m2) – see BNF chart for standard BSAs

Question 7

Formulations & Licensing - 6

Answer 7

1. Often no paediatric strength or oral liquid formulation available, so adult dosage forms manipulated e.g. small doses of adult IV, crushing & dispersing tablets
2. Requires knowledge of solubility, dispersion, enteral feeding tubes.
3. Oral liquids – use concentrated strengths so volume smaller to administer.
4. Consider alternative route e.g. PR paracetamol.
5. Generally prescribed within terms of marketing authorization
6. Human Medicines Regulations 2012 does not prohibit use of unlicensed medicines or off-label use (licensed medicines for unlicensed applications) & this is often necessary

Question 8

Child obesity - 3

Answer 8

1. Consider usual weight should be for patient’s age using heightvs weight centiles & growth charts – boys + girls
2. If unsureuse age-baseddosing where possible and sensible
3. Think aboutthe drugs themselves:Therapeutic levels, toxicity, Considerusing an alternativeprescribing weight.

Question 9

Contraindications in paediatric pharmacy – 5

Answer 9

1. Tetracyclines: contraindicated for under 12, due to deposition in growing bones & teeth causing brittle bones, discoloration of teeth & hypoplasia.
2. Domperidone: risk of QT prolongation. Pediatric warning extrapolated form adult warning & restriction. Still used, but less & at lower dose. Contraindicated when cardiac conduction could be impaired (e.g. cardiac heart failure), meds which prolong QT or sever hepatic impairment
3. Codeine: MHRA warning re: metabolism CYP2D6 risk of ultra fast vs ultra slow metabolisers, use morphine or tramadol
4. Aspirin: Risk of Reyes syndrome (can cause serious liver or brain damage, & death). Used for e.g. Kawasaki disease, cardiac surgery (prevention of thrombus formation) where risk of diseases outweighs risk of Reyes.
5. Metoclopramide: dystonic reactions & extrapyramidal S/Es cardiac. Higher rate in children, treat with Procyclidine

Question 10

General advice for prescription checking - 4

Answer 10

1. Doses & frequency change with age
2. Licensed vs unlicensed
3. Weight required for drug doses
4. Body surface area required for some drugs

Question 11

Renal function calculations in children – Neonate & Child

Answer 11

Neonate
eGFR (ml/min/1.73 squared) = 30xheight,cm / serum[Creatinine mcg/L]
Child >1 month
eGFR (ml/min/1.73 squared) = 35xheight,cm / serum [Creatinine mcg/L]

Question 12

Neonate: Excretion – 7

Answer 12

1. GFR in neonates is LOWER than in adults.
2. GFR & tubular secretion are reduced at birth
3. GFR low in 1st week of life. Rapid changes in GFR seen in first 7-10 days of life. Elimination of drugs by tubular secretion is also reduced.
4. Adaptive change in kidneys when born – they suddenly kick in to action. High creatinine at birth as it is picked up from mum.
5. If renal function is reduced half life of renally excreted drug is increased.
6. Dosing changes often made same ways as adults with poor renal function e.g increasing dosing interval or decreasing dose.
7. Kidneys start to increase in functionality over the first month of life & increases Cl of drugs – requires frequency of some drugs to be increased

Question 13

Neonate: Metabolism – 4

Answer 13

1. Enzyme systems & their maturation vary with age.
2. Some systems are absent at birth whilst other are present that disappear by adulthood.
3. Some systems are present, but reduced as neonates e.g. glucuronidation & oxidation
4. Chloramphenicol normally metabolised by glucuronidation, but this is reduced in neonates, increasing the amount of active drug in the body. This increases risk of toxicity, which can present as grey-baby syndrome, which can cause cyanosis & death. We reserve IV chloramphenicol for life threatening infections.

Question 14

Neonates: Distribution - 2

Answer 14

1. Neonates are water heavy, which causes weight drop after birth, before growth of muscle
2. Proteins are reduced, so dosing must change due to reduced levels of albumin
   e.g. Phenytoin is reduced to match reduced albumin, limiting the amount of fraction of free drug

Question 15

Neonate Absorption: Oral - 3

Answer 15

1. Gastric pH > birth than adults: Drugs are absorbed in their unionized forms.
   Increasing absorption of basic drugs e.g. penicillin.
   Reducing absorption of acidic drugs e.g. phenobarbital.
2. Gastric emptying longer in neonates: Oral absorption of drugs is unpredictable in neonatal period. In neonates, oral medicines usually avoided, until tolerating feeds.
3. Reduced bile salt formation: Reduced bioavailability of lipophilic drugs e.g. diazepam.

Question 16

Neonate Absorption: Rectal - 4

Answer 16

1. Can be poor & erratic.
2. May not have dosage forms for very small patients.
3. Infants have a higher number of rectal contractions than adults.
4. Useful route, when other routes are not available. Paracetamol can be given rectally.

Question 16

Neonate Absorption: Intramuscular – 5

Answer 16

1. Unpredictable as low muscle mass
2. Painful
3. Muscle poorly perfused
4. IM route rarely used in children – exceptions include Vitamin K - useful as slow-release depot action from injection site allows action over several weeks.
5. Useful for avoiding critical doses i.e. ceftriaxone if cannula drops.

Question 17

Neonate Absorption: Topical – 2

Answer 17

1. Absorption through skin is higher in neonates due to reduced thickness & increased permeability.
2. When preparations are applied to skin of infants then potential for systemic absorption of the drug & excipients should always be considered (especially in preterm neonates).

Question 18

ADME In obesity

Answer 18

Absorption - Generally unchanged in people with obesity.

Distribution (Volume of Distribution – Vd) - Altered by drug, body mass, body volume, extracellular water & altered tissue perfusion

Metabolism: Phase I & II altered. Some CYP altered. Clearance changes based on metabolising enzyme. Liver may be worse.

Elimination
Unclear if renal clearance is affected. Some info suggests GFR increase