Prescribing for Children

General prescribing principles for children

teddyPrescribing of any drug in children requires very careful consideration of age, weight, and pharmacologic aspects of the drug in question. Children are particularly susceptible to adverse drug reactions and dosing errors, and this is compounded by the lack of paediatric labelling details for many common prescription drugs. The pharmacokinetics and pharmacodynamics of a given drug is frequently very different in children, compared to adults, and may vary considerably depending on the child’s age and stage of development.

In general, drug dosing in children should be weight-based (mg/kg), though note that the recommended weight-based dose may vary according to age (for example, the half-life of many drugs is prolonged in young infants, compared to older children, resulting in lower recommended doses according to weight). Also, maximum dose limits must be taken into account and for most drugs the adult maximum dose should not be exceeded.

Paediatric dosing tables are included in these guidelines to help determine the optimal dose when antibiotics are required in children. However, these tables do not replace clinical acumen, and doses should be adjusted accordingly if the child’s weight or developmental stage is considered to be outside of the typical values. If in doubt, use the weight-based dosing included in the tables. Usually treatment for children <3months (12 weeks) is not initiated in the community setting. However, dosing information for this age group may be included here for information purposes only and should not be interpreted as a recommendation to prescribe.

Key principles for management of infections in children

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  • Sepsis should always be considered. Sepsis is a clinical syndrome resulting from a dysregulated immune response to infection. Key diagnostic factors include; 
    • Fever or low body temperature
    • Tachypnea
    • Tachycardia
    • Bradycardia (neonates and infants)
  • Clinical assessment, based on the child’s age, history, risk factors, and physical examination, is critical in determining the presence of infection, the likelihood of viral versus bacterial infection, and severity.
  • The vast majority of infections in children are caused by viruses, and antibiotic therapy provides no benefit.
  • For many childhood infections, even when bacteria are implicated, the potential for harm from antibiotic therapy greatly outweighs any potential benefit.
  • Children are less likely to carry resistant bacteria, compared to adults. Thus, where antibiotic therapy is indicated, narrow-spectrum agents should be used as first-line therapy
  • A “watch and wait” approach (+/- a delayed or “only if” prescription) is appropriate for many childhood infections, particularly if clinical assessment indicates a likely viral infection or an infection for which antibiotic therapy is unlikely to be of immediate benefit.
  • Where antibiotic therapy is indicated, using the optimal dose for the shortest possible duration maximises the potential for eradicating the infection while minimising the risk of antibiotic resistance and secondary infections.
  • The age bands for children apply to children of average size. In practice, they will be used alongside other factors such as the severity of the condition being treated and the child's size in relation to the average size of children of the same age.
  • In general, the recommended duration of antibiotics in children is shorter than for similar conditions in adults.

Management of pain and discomfort associated with infection and fever:

  • The use of paracetamol (or ibuprofen if necessary) can be used to help manage pain and distress associated with infection and fever in children.
  • The only purpose for treating fever in children must be to relieve the child’s discomfort and not to lower the body temperature.
  • Paracetamol/Ibuprofen will not prevent febrile convulsions and should not be used specifically for this purpose.
  • Start by giving either paracetamol or ibuprofen.
  • Continue the medication only as long as the child appears distressed.
  • Consider changing to the other agent if the child’s distress is not alleviated.
  • Avoid ibuprofen in children with varicella zoster infection (chicken pox) as there are concerns that NSAIDs increase the risk of serious soft-tissue infections.
  • Paracetamol or Ibuprofen should not be given at the same time. There is limited evidence of effectiveness, potential for confusion, risk of drug administration errors and limited safety data.
  • Only consider alternating these agents if the distress persists or recurs before the next dose is due.
    • I.e Give paracetamol to start with and after an hour their temperature is still high and they are still distressed, try giving them ibuprofen, then paracetamol the next time, then ibuprofen the next time and so on.
  • Give up to four doses of paracetamol over 24 hours and / or up to three doses of ibuprofen over 24 hours if required. Do not give more than this.
    • Leave 4 to 6 hours between each dose of paracetamol and 6 to 8 hours between each dose of ibuprofen.
  • Offer child regular fluids
    • In children who are breastfed, the most appropriate fluid is breast milk
  • Children with fever should avoid creche/school while the child’s fever persists and the creche/school should be notified of the illness.
  • Advice in relation to return to school following a temperature in children during the COVID-19 pandemic is available.
  • Parent/Carer’s advice for management of high temperature in children, including signs of dehydration and when to seek medical advice is available on www.undertheweather.ie
  • The product packaging (& SPC) of paracetamol and ibuprofen, which come in 2 different strengths, contain prescribing details, which are age-based for paracetamol and age-based and weight-based for ibuprofen.
  • Weight-based dosing charts for paracetamol and ibuprofen are available below which may be useful for doctors to use in certain circumstances, and for pharmacists to verify. Doctors can use their clinical judgement to decide when dosing by weight is more appropriate (e.g. for underweight children) as per the dosing charts.

Tables

Amoxicillin

Age

Normal dose

Maximum dose

Maximum dose check
(average weight for age)
Based on 90mg/kg/day

1-11 months

125mg per dose to be given every 8 hours

30mg/kg per dose to be given every 8 hours

1 month (4.3kg):
129mg every 8 hours

11 months (8kg):
240mg every 8 hours

1-4 years

250mg per dose to be given every 8 hours

30mg/kg per dose to be given every 8 hours

1 yr (9kg):
270mg every 8 hours

4 yrs (16kg):
480mg every 8 hours

5-11 years

500mg per dose to be given every 8 hours

30mg/kg* per dose to be given every 8 hours

*Maximum of 1g/dose

5 yrs (18kg):
540mg every 8 hours

11 yrs (35kg):
1g every 8 hours

12-17 years

500mg per dose to be given every 8 hours

1g every 8 hours

1g every 8 hours

Preparations available:
Amoxicillin powder for suspension 125mg/5ml and 250mg/5ml
Capsules: 250mg and 500mg

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Cefalexin 


Age

Normal dose

Maximum dose

Maximum dose check
(average weight for age)
Can be dosed at up to 100mg/kg/day (max 1g QDS) under specialist advice

1-11 months

125mg per dose
to be given every 12 hours

12.5mg/kg/per dose to be given every 12 hours

1 month (4.3kg):
430mg/day

11 months (8kg):
800mg/day

1-4 years

125mg per dose to be given every 8 hours

12.5mg/kg/per dose to be given every 12 hours

1 yr (9kg):
900mg/day

4 yrs (16kg):
1600mg/day

5-11 years

250mg per dose to be given every 8 hours

12.5mg/kg/per dose to be given every 12 hours

5 yrs (18kg):
1800mg/day

11 yrs (35kg):
3500mg/day

Max. per dose 1 g every 6 hours

12-17 years

500mg per dose to be given every 8 - 12 hours

1-1.5g every 6 -8  hours

1-1.5g every 6-8  hours

Preparations available:
Cefalexin 125mg/5ml and 250mg/5ml powder for oral suspension,
Capsules: 250mg and 500mg

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Clarithromycin

Age

Normal dose

Maximum dose check
(average weight for age)

1-11 months 

7.5mg/kg per dose to be given every 12 hours

1 month (4.3kg):
32.25mg every 12 hours

11 months (8kg):
60mg every 12 hours

1-2 years

62.5mg per dose to be given every 12 hours

3-6 years

125mg per dose to be given every 12 hours

7-9 years

187.5mg per dose to be given every 12 hours

10-12 years

250mg per dose to be given every 12 hours

>12-17 years

250 - 500mg per dose to be given every 12 hours

Preparations available:
Clarithromycin Granules for Oral Solution: 125mg/5mls and 250mg/5mls.
Tablets: 250mg and 500mg.
Prolonged release tablets not recommended in children <12 years.

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Co-amoxiclav 

*Three times daily (TDS) 125/31.25 mg in 5mL Oral Suspension Dosing Table*

Warning: In the small number of instances where Amoxicillin/clavulanic acid is indicated, a twice daily preparation of Amoxicillin/clavulanic acid 400/57 mg in 5 ml is not recommended for first line therapy

Children aged less than 2 years

*NB: Dose expressed as amoxicillin/clavulanic acid combined i.e. 156 mg = 125 mg amoxicillin + 31.25 mg clavulanic acid in 5 mL

Weight

Mild-moderate infection
8.3 mg/kg* TDS

Severe infection
16.7 mg/kg* TDS

Dose in mg Dose in mL Dose in mg Dose in mL
2 kg 17 mg* TDS 0.5 mL TDS 33 mg* TDS 1.1 mL TDS
3 kg 25 mg* TDS 0.8 mL TDS 50 mg* TDS 1.6 mL TDS
4 kg 33 mg* TDS 1.1 mL TDS 67 mg* TDS 2.1 mL TDS
5 kg 42 mg* TDS 1.3 mL TDS 84 mg* TDS 2.7 mL TDS
6 kg 50 mg* TDS 1.6 mL TDS 100 mg* TDS 3.2 mL TDS
7 kg 58 mg* TDS 1.9 mL TDS 117 mg* TDS 3.7 mL TDS
8 kg 66 mg* TDS 2.1 mL TDS 134 mg* TDS 4.3 mL TDS
9 kg 75 mg* TDS 2.4 mL TDS 150 mg* TDS 4.8 mL TDS
10 kg 83 mg* TDS 2.7 mL TDS 167 mg* TDS 5.4 mL TDS
11 kg 91 mg* TDS 2.9 mL TDS 184 mg* TDS 5.9 mL TDS
12 kg 100 mg* TDS 3.2 mL TDS 200 mg* TDS 6.4 mL TDS
13 kg 108 mg* TDS 3.5 mL TDS 217 mg* TDS 7 mL TDS
14 kg 116 mg* TDS 3.7 mL TDS 234 mg* TDS 7.5 mL TDS
15 kg 125 mg* TDS 4 mL TDS 251 mg* TDS 8 mL TDS
Children Aged 2-12 years and weighing less than 40kg

*NB: Dose expressed as amoxicillin/clavulanic acid combined i.e. 156mg = 125mg amoxicillin + 31.25mg clavulanic acid in 5 mL

Age Mild-moderate infection Severe infection
Dose in mg Dose in mL Dose in mg Dose in mL
1-5 years (>15kg) 156 mg* TDS 5 mL TDS 312 mg* TDS 10 mL TDS
6-12 years** 312 mg* TDS 10 mL TDS 625 mg* TDS 20 mL TDS

**In 6- 12 years you may wish to consider a twice daily (BD) dosing formulation (of ratio 7:1 such as Augmentin Duo ®) of amoxicillin-clavulanic acid to reduce volume of suspension necessary for correct dose. Consult with pharmacist to calculate dose

Children >12 years, OR weighing 40 kg or greater, and Adults:

625 mg TDS (tablet formulation: 625 mg = amoxicillin/clavulanic acid 500/125 mg) or 625 mg TDS (20 mL TDS of amoxicillin/clavulanic acid 125/31.25 mg in 5 mL)

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Doxycycline 

(excluding Lyme Disease – see Lyme Disease page for specific guidance)
Age Normal dose Maximum dose check:
(average weight for age*)

8 <12 years

<45kg:
Day 1: 4.4mg/kg/day in 1-2 divided doses.
Day 2 onwards: 2.2mg/kg/day in 1-2 divided doses.

≥45kg:
Day 1: 200 mg daily in 1–2 divided doses.
Day 2 onwards: 100 mg daily.

8 years (26kg)*
Day 1: 114.4mg/day
Day 2 onwards: 57.2mg/day

12 years (39kg)*
Day 1: 171.6mg/day
Day 2 onwards: 85.8mg/day

For 44kg weight:
Day 1: 193.6mg/day
Day 2 onwards: 96.8kg/day

12- 17 years

Day 1: 200 mg daily in 1–2 divided doses.
Day 2 onwards: 100 mg daily.

As per normal dose

Preparations available:
Doxycycline capsules/tablets 50mg & 100mg 
Dispersible tablets 100mg. This is an unlicensed product, check availability with community pharmacist.

Sample calculation (information for dispensing pharmacist)

Child requiring treatment using Doxycycline 100mg unlicensed dispersible tablets:
Child weight=30kg (specify child weight on prescription)
Dose: 4.4mg per kg
30kg x 4.4mg/kg = 132mg dose required i.e. 100mg + 32mg

How to disperse tablet to give a part dose of 32mg:
Dissolve 1x 100mg dispersible doxycycline tablet in 5mL of water.
100mg=5mL so 32mg=1.6mL.(Draw up and give 1.6ml using 5ml syringe supplied by pharmacist to give 32mg).

Therefore for a total dose of 132mg, give the appropriately dispersed 100mg tablet plus 1.6mL (32mg) of the dispersed liquid prepared as above.

Discard remaining dose by returning to local pharmacy in child resistant closure container. If required, to improve palatability, can add squash/fruit juice to water. Make dose fresh each time.

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Flucloxacillin 

Age

Normal dose

Maximum dose check
(average weight for age)

1 month- < 2 years

62.5mg - 125mg per dose
to be given every 6 hours

125mg per dose
to be given every 6 hours

2-10 years

125mg-250mg per dose
to be given every 6 hours

250mg per dose
to be given every 6 hours

10-17 years

250mg-500mg per dose
to be given every 6 hours

500mg per dose
to be given every 6 hours

Preparations available:
Flucloxacillin capsules 500mg
Flucloxacillin powder for oral suspension: 125mg/5ml and 250mg/5ml

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Metronidazole – for treatment of anaerobic (non-dental) infections 

Age Normal dose Maximum dose check
(average weight for age)
1-2 months  7.5mg/kg per dose
to be given every 12 hours

1month (4.3kg):
32.25mg every 12 hours

2 months (5.4kg):
40.5mg every 12 hours

≥2 months-12 years 7.5mg/kg per dose every 8 hours

2 months (5.4kg):
40.5mg every 8 hours

12 yrs (39kg):
Max of 400mg every 8 hours

12-17 years 400mg every 8 hours Max 400mg every 8 hours

Preparations available:
Metronidazole tablets 200mg & 400mg
Metronidazole liquid 200mg/5ml strength*

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Nitrofurantoin 

Age

Normal dose

Maximum dose check:
(average weight for age)

3 – 5 months

0.75mg/kg per dose
to be given every 6 hours

3 months (5kg):
3.75mg to be given every 6 hours

5 months (7kg):
5.25mg to be given every 6 hours

6 months-3 years

0.75mg/kg per dose
to be given every 6 hours

6 months (8kg):
6mg to be given every 6 hours

3 years (14kg):
10.5mg to be given every 6 hours

4-7 years

0.75mg/kg per dose
to be given every 6 hours

4 years (16kg):
12mg to be given every 6 hours

7 years (23kg):
17.25mg to be given every 6 hours

8-12 years

0.75mg/kg per dose
to be given every 6 hours

8 years (26kg):
19.5mg to be given every 6 hours

12 years (39kg):
29.25mg to be given every 6 hours

>12 years and adults

50mg to be given every 6 hours (using immediate release product)
Or
100mg every 12 hours (using the modified-release product)

Preparations available:
Nitrofurantoin 50mg immediate release tablets
Nitrofurantoin 100mg modified release capsules

Unlicensed Nitrofurantoin 25mg/5ml oral suspension available for children. Consult with pharmacist regarding availability and pricing.

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Phenoxymethylpenicillin (Penicillin V) 

Age

Normal dose

Maximum dose

Maximum dose check
Based on 12.5mg/kg every 6 hours

1-11 months

62.5mg per dose to be given every 6 hours 12.5 mg/kg per dose to be given every 6 hours

1 month (4.3kg):
53.75mg every 6 hours

11 months (8kg):
100mg every 6 hours

1-5 years

125mg per dose to be given every 6 hours

12.5 mg/kg per dose to be given every 6 hours

1 yr (9kg):
112.5mg every 6 hours

5 yrs (18kg):
225mg every 6 hours

6-11 years

250mg per dose to be given every 6 hours (Kopen tablet or liquid preparation)

or

333mg per dose to be given every 6 hours
(Calvepen tablet)

12.5 mg/kg per dose to be given every 6 hours

6 yrs (20kg):
250mg every 6 hours

12 yrs (39kg):
487.5mg every 6 hours

≥12 years and Adults

500mg per dose to be given every 6 hours
(Kopen tablet or liquid preparation)

or

666mg per dose to be given every 6 hours
(Calvepen tablet)

12.5 mg/kg per dose to be given every 6 hours

As per normal dose

Preparation available:
Phenoxymethylpenicillin powder for oral solution: 125mg/5ml, 250mg/5ml. Tablets: Kopen ® 250mg,  Calvepen® 333mg and 666mg
(Note: Calvepen® 333mg tablet = 300mg phenoxymethylpenicillin,
Calvepen® 666mg tablet = 600mg phenoxymethylpenicillin)*

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Trimethoprim

Age                                   

Normal dose:
3mg/kg every 12 hours

Maximum dose

Maximum dose check:
Based on max. of 4mg/kg every 12 hours

6 weeks – 5 months

25mg every 12 hours

4mg/kg every 12 hours

6 weeks (5kg):
20mg every 12 hours

5 months (7kg):
28mg every 12 hours

6 months – 3 years

25 - 50mg every 12 hours

4mg/kg every 12 hours

6 months (8kg):
32mg every 12 hours

3 years (14kg):
56mg every 12 hours

4-7 years

50 - 75mg every 12 hours

4mg/kg every 12 hours

4 years (16kg):
64mg every 12 hours

7 years (23kg):
92mg every 12 hours

8-12 years

75 - 125mg every 12 hours

4mg/kg
every 12 hours

8 years (26kg):
104mg every 12 hours

12 years (39kg):
156mg every 12 hours

>12 years and Adults

200mg every 12 hours

200mg every 12 hours

Preparations available:
Trimethoprim 10mg/ml oral solution
Trimethoprim 100mg and 200mg tablets

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Weight and Height Table, Adapted from BNF for Children accessed via Medicines Complete (last updated 08 March 2022)

The table shows the mean values for weight and height and gender by age; these values may be used to calculate doses in the absence of actual measurements. However, the child’s actual weight and height might vary considerably from the values in the table and it is important to see the child to ensure that the value chosen is appropriate. In most cases the child’s actual measurement should be obtained as soon as possible and the dose re-calculated.

Age Weight (kg) Height (cm)
Full-term neonate 3.5 51
1 month 4.3 55
2 months 5.4 58
3 months 6.1 61
4 months 6.7 63
6 months 7.6 67
1 year 9 75
3 years 14 96
5 years 18 109
7 years 23 122
10 years 32 138
12 years 39 149
14 year-old boy 49 163
14 year-old girl 50 159
Adult male 68 176
Adult Female 58 164

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Conversion to units table 

Approximate conversions and units
lb kg stones kg ml fl oz
1 0.45 1 6.35 50 1.8
2 0.91 2 12.7 100 3.5
3 1.36 3 19.05 150 5.3
4 1.81 4 25.40 200 7.0
5 2.27 5 31.75 500 17.6
6 2.72 6 38.10 1000 35.2
7 3.18 7 44.45
8 3.63 8 50.80
9 4.08 9 57.15
10 4.54 10 63.50
11 4.99 11 69.85
12 5.44 12 76.20
13 5.90 13 82.55
14 6.35 14 88.90
15 95.25

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Page reviewed March 2022

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