New research carried out jointly by researchers at King's College London, St George's, University of London and Imperial College London has revealed that millions of children in the UK are potentially receiving penicillin prescriptions below the recommended dose for common infections.
The study is the first to examine prescribing of oral penicillin, the most commonly prescribed antibiotic for children, by GPs in the UK.
The researchers found that of the children under the age of one who were prescribed the oral penicillin none were prescribed the dose of 62.5mg recommended by the British National Formulary for Children (BNFC). In fact, the majority received double the recommended dose (125 mg).
Of children aged one to five 96 per cent received the recommended dose but 40 per cent of 6-12 year olds and 70 per cent of 12-18 year olds were prescribed unit-doses below the BNFC guidelines. Similar patterns of prescribing were found for penicillin V and flucloxacillin.
The study also looked specifically at prescriptions for ear infection, the most common condition in childhood that can lead to the prescription of oral penicillin, and found that children under the age of one were the only group who received the recommended dose of amoxicillin. For children aged 4-15 years the prescriptions equated to approximately 33 per cent of the recommended dose.
Dosing guidelines for oral penicillin are currently provided by the BNFC and are determined by age and weight-bands. Although guidelines specifically for amoxicillin did change late last year, the authors suggest this has only made the situation worse, particularly in the approval of a new, wider 5-18 age band.
Dr Paul Long, Reader in Pharmacognosy at King's College London, said: '12-18 year olds should have received a 500mg dose based on pre-2013 guidance but our study shows that many of these teenagers were actually prescribed 250mg. Introducing a new 5-18 age band would seemingly justify a 250mg prescribing practice, but actually only further exacerbates potential under-dosing in the 12-18 age group.'
The researchers also point out that another problem with the current guidelines is that they do not take into account how the average weight of children has changed over time. Due to the rising prevalence of childhood obesity, prescriptions based on age-bands could lead to doses prescribed at too low a level to produce a therapeutic effect (sub-therapeutic dosing).
The guidelines for adult penicillin prescription has been re-evaluated to take modern weights into consideration but the recommended dose for children based on age banding has been in place since the 1960’s
Dr Long of King's College London said: “Although oral penicillins have been widely used for over 50 years to treat infections in children, the dosing guidelines have remained complicated, which carries the risk of confusing prescribers. Age and weight bands are well established but there is no standardised or evidence-based guideline to clarify which method of dose selection is best.”
“The need to review these guidelines is more urgent than ever as it is clear from our research that age-banding doses is no longer appropriate.”
“A detailed qualitative assessment of prescriber practice is also required to understand reasons for the use of age-bands and the barriers to implementation of weight-based dosing.”
Dr Sonia Saxena, from the School of Public Health, Imperial College London and a practising GP, said: 'It is important now to understand why GPs are prescribing sub-therapeutic levels of penicillin. Some GPs may be erring on the side of caution, prescribing low doses to avoid errors or side effects.'
Dr Saxena added: “In the majority of cases children will still get better, but undertreating those children who do need antibiotics could mean more infectious complications and more health contacts overall.”
The study was funded by the National Institute for Health Research (NIHR) Biomedical Research Centre at Guy's and St Thomas' NHS Foundation Trust and King's College London and was published in the British Journal of General Practic.