Paediatric Prescribing Flashcards
Why should aspirin be avoided in children?
Associated with Reyes Syndrome (excessive vomiting, tachypnoea, seizures, anxiety, hallucinations, irritability)
How is GI motility (and therefore oral absorption) different in neonates and infants?
Gastric emptying is slower so there is increased oral absorption
How is the luminal pH different in children under 3 years and how does this affect oral drug absorption?
After birth the gut pH is >4 which increases the absorption of acid-labile drugs.
Why do topical drugs have a greater systemic effect in children?
Skin in thinner so more percutaneous absorption can occur
Larger surface area of skin relative to body weight
Why are IM drugs more rapidly absorbed in children?
Increased capillary density in muscles so increased take up of drug into bloodstream
Why are inhaled drugs more rapidly absorbed in children?
The lungs are immature so drugs can enter the bloodstream more easily
How does % body water (and therefore volume of distribution) change from a premature neonate to an adult?
Premature neonate - 80% water
Full term - 70% water
10 years old- 65% water
Adult- 54% water
In infants the volume of distribution is higher and so water soluble drugs will be at a lower concentration in the body.
Give 3 reasons why paediatric prescribing errors may occur
Doses are calculated individually off weight
Drugs are commonly prescribed off label
Shortage of paediatric clinical trials
Drugs not available in child friendly forms
Give a risk of prescribing ibuprofen in children who are dehydrated
Renal damage
How does fewer plasma proteins in the blood affect drug distribution in infants?
Fewer plasma proteins means more free/unbound drug in the plasma to exert therapeutic effects
Give 5 factors that affect drug distribution in the body
% body water Plasma proteins Regional blood flow Organ perfusion Cell membrane properties Cardiac output Acid-base balance
Before the age of 3 how does the gastric pH affect drug absorption?
<3 years old- pH >4 which increases absorption of acid-labile drugs.
After 3 years, pH drops to 1-2
Why can caffeine only be used as a respiratory stimulant before 3 months of life?
At 3 months old, the liver enzyme CYP1A2 develops which demethylates caffeine and starts phase 1 metabolism.
What is the GFR of a term neonate?
2-4 ml/min/1.73squared
How does a low neonatal GFR affect drug excretion?
Low GFR means renally excreted drugs will remain in the body for much longer
How can weight be estimated in a child for emergency drug prescribing?
(Age + 4) x 2
Or:
0-12 months: (0.5 x age in months) + 4
1-5 years: (2 x age in years) + 8
6-12 years: (3 x age in years) + 7
How is weight estimated from length in infants?
Use Breslow tape
How is Body Surface Area calculated in infants?
Uses weight only- conversion chart in BNFC
Why is body surface area used over weight in dosing toxic drugs like chemotherapy?
Thought to correlate more closely with variation in age, body size and body composition
Which fluids are given as routine maintenance fluids in children?
0.9% Sodium Chloride
Isotonic crystalloid
How is the maintenance fluid dose over 24 hours calculated in children?
100 ml/kg for 1st 10 kg
50 ml/kg for next 10 kg
20 ml/kg for every remaining kg
Add together and divide by 24 to get the hourly rate.
How are maintenance fluids decided in neonates?
Depends on gestation, day of life, weight, BM and electrolytes.
Usually given 0.9% NaCl with 5-10% of glucose
Give 4 red flag indicators that a child needs IV rehydration
Appears unwell Lethargic Sunken eyes Tachycardia Tachypnoea Reduced skin turgor
If rehydrating orally, how much should be given over 4 hours?
50 ml per kg in small frequent drinks or via NG tube
If rehydrating parentally (IV), how much of what fluid should be given over 24 hours?
50 ml/kg of 0.9% sodium chloride + 5% glucose over 24 hours
+ maintenance fluids
If a patient is in shock, what bolus of fluid is given before rehydration and maintenance fluids are started?
20 ml/kg bolus of 0.9% saline
Increase rehydration fluids to 100 ml/kg
What is an off label drug?
Drug used for conditions outside marketing authorisation
What is an unlicensed drug?
Drug with no marketing authorisation
What criteria must be met to prescribe an off label or unlicensed drug?
No suitable licenced alternative
Sufficient evidence for its use
You take responsibility for prescription and patient care
Decision and rational documented in notes
Inform patient and parent and get consent.
Give 4 ways to avoid paediatric prescribing errors
Check doses against BNFC Check allergies Check weight, age, BSA Avoid decimal points Get 2nd person to check Write clearly Write out units in full Round doses to a sensible value
How can adherence be improved in children?
Shorter courses
Time doses to avoid school
Avoid unacceptable side effects
Age appropriate information
Nicer taste/ better administration methods
Educate parents on importance of adherence
