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.

Key principles for management of infections in children

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  • 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
  • In general, the recommended duration of antibiotics in children is shorter than for similar conditions in adults

Tables


Amoxicillin

Age

Normal dose

Maximum dose

Maximum dose check
(average weight for age)

1-11 months

125mg per dose
to be given 3 times daily

30mg/kg per dose
to be given 3 times daily

1 month (4.3kg)
125mg 3 times daily

11 months (8kg)
250mg 3 times daily

1-4 years

250mg per dose
to be given 3 times daily

30mg/kg per dose
to be given 3 times daily

1 yr (9kg)
250mg 3 times daily

4 yrs (16kg)
500mg 3 times daily

5-11 years

500mg per dose
to be given 3 times daily

30mg/kg per dose
to be given 3 times daily

5 yrs (18kg)
500mg 3 times daily

11 yrs (35kg)
1g 3 times daily

12-17 years

500mg per dose
to be given 3 times daily

1g 3 times daily

1g 3 times daily

Preparations available:
Amoxicillin powder for suspension 125mg/5ml, 250mg/5ml and 125mg/1.25ml
Capsules: 250mg and 500mg

Click here for PDF of the Amoxicillin Table

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Penicillin

Age

Normal dose

Maximum dose

Maximum dose check

1-11 months

62.5mg per dose
to be given 4 times daily
12.5 mg/kg per dose
to be given 4 times a day

11 months (8kg)
max 100mg 4 times daily

1-5 years

125mg per dose
to be given 4 times daily

12.5 mg/kg per dose
to be given 4 times a day

1 yr (9kg)
max 125mg 4 times daily

5 yrs (18kg)
max 225mg 4 times daily

6-12 years

250mg per dose to
be given 4 times daily

12.5 mg/kg per dose
to be given 4 times a day

6 yrs (20kg)
max 250mg 4 times daily

12 yrs (39kg)
max 500mg 4 times daily

≥12 years and Adults

500mg per dose
to be given 4 times daily

OR

666mg per dose
to be given 4 times daily

(Calvepen tablet)

12.5 mg/kg per dose
to be given 4 times a day

max 1 g 4 times a day

Products for children: Phenoxymethylpenicillin powder for oral solution: 125mg/5ml, 250mg/5ml.
Tablets: 250mg, 333mg and 666mg (333mg tablet is equivalent to 250mg of suspension)

Click here for the PDF of the Penicillin table

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Trimethoprim

Age                                   

Normal dose:
4mg/kg BD

Dose check:
(average weight for age)
4mg/kg BD

6 weeks – 5 months

4mg/kg per dose
to be given twice daily

6 weeks (5kg)
20mg BD

5 months (7kg)
30mg BD

6 months – 3 years

4mg/kg per dose
to be given twice daily

6 months (8kg)
30mg BD

3 years (14kg)
60mg BD

4-7 years

4mg/kg per dose
to be given twice daily

4 years (16kg)
60mg BD

7 years (23kg)
90mg BD

8-12 years

4mg/kg per dose
to be given twice daily

8 years (26kg)
100mg BD

12 years (39kg)
160mg BD

>12 years and Adults

200mg BD

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

Click here for the PDF of the Trimethoprim table

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Cefalexin

Age

Normal dose

Maximum dose

Maximum dose check
(average weight for age)

1-11 months

75mg-125mg per dose
to be given 3 times daily

17mg/kg/per dose
to be given 3 times daily

1 month (4.3kg)
75mg 3 times daily

11 months (8kg)
125mg 3 times daily

1-4 years

125mg per dose
to be given 3 times daily

17mg/kg/per dose
to be given 3 times daily

1 yr (9kg)
150mg 3 times daily

4 yrs (16kg)
250mg 3 times daily

5-11 years

250mg per dose
to be given 3 times daily

17mg/kg/per dose
to be given 3 times daily

5 yrs (18kg)
300mg 3 times daily

11 yrs (35kg)
500mg 3 times daily

12-17 years

500mg per dose
to be given 3 times daily

 

1-1.5g
3 to 4 times daily

(max. 1g
4 times daily)

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

Click here for the PDF of the Cefalexin table

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Nitrofurantoin

For uncomplicated urinary tract infections in children: Duration: 3 days

Age

Normal dose

Dose check:
(average weight for age)

0.75mg/kg 4 times daily
(round to nearest 5mg)

3 – 5 months

0.75mg/kg per dose
to be given 4 times daily

(5-7kg): 5mg
to be given 4 times daily

6 months-3 years

0.75mg/kg per dose
to be given 4 times daily

6 months (8kg)
5mg to be given 4 times daily

3 years (14kg)
10mg to be given 4 times daily

4-7 years

0.75mg/kg per dose
to be given 4 times daily

4 years (16kg)
10mg to be given 4 times daily

7 years (23kg)
15mg to be given 4 times daily

8-12 years

0.75mg/kg per dose
to be given 4 times daily

8 years (26kg)
20mg to be given 4 times daily

12 years (39kg)
30mg to be given 4 times daily

>12 years and adults

50mg to be given 4 times daily

Products available: 50mg and 100mg capsules

Unlicensed oral suspension available for children. Consult with pharmacist regarding availability and pricing.

Click here for the PDF of the Nitrofurantoin table

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Flucloxacillin

Age

Normal dose

1 month-1 year

62.5mg - 125mg per dose
to be given 4 times daily

2-9 years

125mg-250mg per dose
to be given 4 times daily

10-17 years

250mg-500mg per dose
to be given 4 times daily

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

Click here for the PDF of the Flucloxacillin table

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Clarithromycin

Approximate Age

Weight

Dose®

1-2 years

8-11kg

62.5mg per dose
to be given twice daily

3-6 years

12-19kg

125mg per dose
to be given twice daily

7-9 years

20-29kg

187.5mg per dose
to be given twice daily

10-12 years

30-40kg

250mg per dose
to be given twice daily

(®Dose is based on 7.5mg/kg per dose twice daily)
Preparations available: Clarithromycin Granules for Oral Solution: 125mg/5mls and 250mg/5mls.
Tablets: 250mg and 500mg. Prolonged release tablets not recommended in children.

Click here for the PDF of the Clarithromycin table


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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.

 Weight and Height Table, Adapted from BNF 70 for children 2009

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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Click here to view the Antipyretic Prescribing document

Author: Mooney, Shonagh Dr.; ICGP Quality in Practice Committee

Publication Year: 2013


Page reviewed September 2017

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