Nearly one in five oral penicillin doses given to children in NHS hospitals may be too high or too low

Because children's weights vary for a given age doses may be too low in heavier children, which could result in treatment being ineffective or risk promoting antibiotic resistance, according to a collaborative study published in the BMJ by researchers from St George's, University of London, Imperial College London, University College London and King's College London

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

The study authors found that commonly used methods to decide doses of oral antibiotics for children in hospitals in the UK could result in up to 18% of children receiving doses outside the recommended range.

Professor Mike Sharland senior author of the study said: "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. Selecting the best dose is essential for antibiotics to be effective, reduce the risk of side effects and impact on antibiotic resistance which might prevent effective treatment for life threatening illnesses in the future."

Current UK guidelines typically recommend using the age of the child to guide the dose of antibiotics such as amoxicillin, which could mean that 11% receive higher doses than needed and 7% are under dosed.

In other countries, such as in Africa where the average weights of children are lower, use of age bands could lead to every third child being prescribed a dose above the maximum recommendation of 90 mg/kg amoxicillin per day. Choosing doses according to a weight band that includes the child's weight is recommended by the WHO and was found to be more accurate, such that only 8% of UK children and 4% of African children would have received a total daily dose below the recommended range.

The challenge is to keep childhood antibiotic dosing guidance simple without compromising accuracy, and it is crucial to identify the best approach towards this across different settings globally. The researchers suggest that weight-bands may be a robust way forward, and further international debate is needed to identify a common, widely applicable and acceptable approach.