Penicillin dosing guidelines for children need to be reviewed to reflect the increase in children's average weight over the past few decades, an article in the British Medical Journal suggests.
The guidelines have not been altered for nearly 50 years and are mainly based on a child's weight.
However, scientists and clinicians at King's College London and St George's, University of London, say that the average weight of children has increased over time and that a review of the guidelines is therefore essential to ensure children receive effective doses of penicillin.
The experts conducted a review of evidence and found that prescribing based on age bands was first suggested in the early 1950s, with a general recommendation published in the British Medical Journal in 1963 and still standing today.
The age band guidelines are accompanied by average rates: birth to one year (10kg); two years (13kg); five years (18kg); and ten years (30kg).
However, figures from the Health Survey for England 2009 indicate that the average five-year-old now weighs 21kg, while the average ten-year-old weighs 37kg.
This suggests that some children may not be receiving effective doses of penicillin, contributing to failed treatment and antibiotic resistance.
Dr Paul Long, senior lecturer in pharmacognosy at King's College London, said: 'Children's average size and weight are slowly but significantly changing, so what may have been adequate doses of penicillin 50 years ago are potentially not enough today.
'If we want to be sure that we are treating childhood bacterial infections effectively, the evidence base behind these prescribing guidelines needs to be improved, and the recommended doses reviewed accordingly.'
Simon Keady, a spokesman for the Royal Pharmaceutical Society, said that penicillin's long history of use 'should not stop us from continuing to identify the most appropriate dose'.