Aims The British National Formulary for Children (BNFC) provides recommendations for dosing oral penicillins in children according to age-bands, weight-bands, and weight-based calculations. However, as childhood obesity is increasingly prevalent, dosing by age-bands could lead to clinically significant under-dosing. This study aimed to determine how current UK GP prescribing practise follows the original age-band dosing recommendations, which could lead to sub-therapeutic dosing.
Methods Detailed prescriptions for the oral penicillins in 0–18 year-old children from 2010 were analysed from the IMS Disease-Analyzer database, which contains computerised medical records from 125 general practises, representing approximately 2% of the UK population. It includes data on formulation, strength, prescription quantity unit, package size, prescribed quantity and volume.
Results For 2010, 388,926 patients aged 0–18 years were registered on the database (51% male), accounting for 376,292 person-years in total. There were 65,737 prescriptions for oral penicillins identified: amoxicillin (63%), penicillin V (17%) and flucloxacillin (20%).
The amoxicillin prescription results by age-band (as an example) showed:
In the first age-band of less than 1 year, no child received an amoxicillin prescription for the recommended unit dose of 62.5 mg; the majority received double the unit dose (125 mg);
In the second age-band of 1 to 5 years, 96% received prescriptions for the recommended unit dose (125 mg);
40% of 6–12 year-olds and 70% of 12–18 year-olds were prescribed unit doses below those recommended in the BNFC for their age-band.
Prescriptions for otitis media were analysed separately. As patient weight was not available, average weights were used for the analysis (based on the 2010 Health Survey of England), and the dose in mg/kg/day was calculated. From these data, only children less than 1 year received the recommended BNFC dose of 40–90 mg/kg/day. For children aged 4–15 years, the prescriptions equated to 10–20 mg/kg/day, approximately 33% of the recommended dose.
Conclusions These results demonstrate wide variation in the dosing of penicillins for children in primary care. There is an urgent need to review and simplify current dosing ecommendations according to age-bands and weight-bands, in relation to the average weights of children today.