Intended for healthcare professionals

Feature Christmas 2011: Oral Traditions

Dosing of oral penicillins in children: is big child=half an adult, small child=half a big child, baby=half a small child still the best we can do?

BMJ 2011; 343 doi: (Published 15 December 2011) Cite this as: BMJ 2011;343:d7803
  1. Umar Ahmed, pharmacist12,
  2. Nikos Spyridis, consultant in paediatric infectious diseases34,
  3. Ian C K Wong, professor of paediatric medicines research15,
  4. Mike Sharland, professor of paediatric infectious diseases3,
  5. Paul F Long, senior lecturer in pharmacognosy16
  6. on behalf of the improving Children’s Antibiotic Prescribing UK Research Network (iCAP)
  1. 1Centre for Paediatric Pharmacy Research, School of Pharmacy, University of London, London WC1H 9JP, UK
  2. 2Boots The Chemist, London, UK
  3. 3Paediatric Infectious Diseases Unit, St George’s Hospital, London, UK
  4. 4P and A Kyriakou Children’s Hospital, University of Athens, Athens, Greece
  5. 5Department of Pharmacology and Pharmacy, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
  6. 6Institute of Pharmaceutical Science and Department of Chemistry, King’s College London, London, UK
  1. Correspondence to: P F Long paul.long{at}

The improving Children’s Antibiotic Prescribing UK Research Network thinks it’s time to abandon this historical rule of thumb

The penicillins have been the most important antibiotics used in children for over 50 years. As well as combating the rapid emergence of penicillinase producing bacteria, the development of penicillin derivatives in the 1950s and 1960s allowed oral dosing, removing the need for painful intramuscular injections. Penicillin V, flucloxacillin, and amoxicillin account for nearly 4.5 million of the 6 million prescriptions for oral antibiotics given to children in England each year.1

Despite their wide use over many decades, guidance on the correct dose of oral penicillins for children remains confusing. For example, the 2011 summary of product characteristics for Amoxil paediatric suspension in children weighing <40 kg is 40-90 mg/kg/day for all indications,2 whereas recommendations for amoxicillin, penicillin V, and flucloxacillin in the British National Formulary for Children are mostly based on age bands, although weight bands or weight based calculations (mg/kg) are given for some indications. The widely used doses of 62.5 mg or 125 mg are fractions of the adult dose recommended in the British National Formulary (BNF) and are still based on the original dosing principle of a big child=half an adult, small child=half a big child, baby=half a small child .

Fiona Blair
Fiona Blair
Fiona Blair

Limited evidence for dosing regimens

To understand the origins of the age band dosing schedule, we conducted a historical review of the literature and earlier UK prescribing formularies. This comprised an electronic search of PubMed (using a combination of terms including the antibiotic name, child/paediatric, dose, clinical trial, review, pharmacokinetic) and the summary of product characteristics, a manual search through the archives of the Royal Pharmaceutical Society of Great Britain and British Medical Association, and requests for dosing information submitted under the freedom of information acts to …

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