Antibiotic doses given to children in hospitals may be too high or too low

Nearly one in five children may receive an inappropriate dose of antibiotic, potentially making it less effective or raising risk of side effects.

According to a new study, published today, this is because doctors follow drug dosing guidelines - formulated 50 years ago - that use age, rather than weight.

However, because children’s weights vary for a given age – and average weights have changed in the past 50 years - doses may be too low in heavier children. This could result in treatment being ineffective or risk promoting antibiotic resistance.

Moreover, children with lower weights could suffer unnecessary side effects from too high a dose.

The paper is published in the British Medical Journal, by researchers from Imperial College London, St George’s, University of London, University College London and King's College London.

In the research, the authors studied age and weight data of children from 61 UK paediatric units in NHS hospitals. First, they calculated the dose of amoxicillin (a type of penicillin, and the most commonly used antibiotic in children) based on age alone. This is the method UK guidelines currently recommend.

Then, they re-calculated the children’s doses based on weight alone. Weight is considered the gold-standard for drug prescribing, and is recommended by the World Health Organisation.

According to calculations by the authors, using the UK age-based guidelines could mean that 11 per cent of children receive higher doses than needed, and 7 per cent are under dosed.

Previous work, from the same team, suggested that the doses of antibiotics prescribed by GPs may also be too high or low, due to age-based prescribing.

Dr Sonia Saxena, a practising GP and clinical reader from Imperial’s School of Public Health said: “We have already reported widespread under-dosing of antibiotics prescribed for children in the community in the UK. This study adds to that by showing age banded doses result in many hospitalised children receiving too much or too little. That means the treatment risks being ineffective if the dose is too low and even encourage bacterial resistance to develop.  Or if the dose is too high a child is more likely to have side effects, such as diarrhoea, and that might mean they are less likely to continue with the treatment. Taken together, it does suggest the guidance needs to be urgently reviewed and recalculated so we move away from an age-based system to a weight-based system as used in many other countries."

Professor Mike Sharland, senior author of the study from St George’s University added: “Parents can be reassured that most children in hospital will be getting the correct doses of antibiotics needed. The responsibility for prescribing ultimately falls on the prescriber, but parents can help by providing information about their child’s weight. Pharmacists may also have a role in checking the accuracy of doses of the medicines they are dispensing to children.”

The team also studied age and weight data from children in African paediatric units, and found that use of age bands could lead to every third child being prescribed a dose above the maximum recommendation daily dose of amoxicillin.

'Not too little, not too much: problems of selecting oral antibiotic dose for children', by J.A Bielicki, C.I.S Barker, S Saxena, I.C.K Wong, P.F Long and M. Sharland is published in the BMJ.