A
practical overview of the evidence and considerations regarding safe prescribing for children with obesity, with examples of commonly affected medicines
Childhood obesity is a major public health challenge in the UK, with
important implications for medicines use and safety. In England, 12% of
children aged 2–10 years and 19% of young people aged 11–15 years were
classified as obese in 20221.
The latest National Child Measurement Programme data, published in
2024, show obesity rates of 9.6% in reception-aged children (i.e.
children aged four to five years) and 22.1% in Year 6 (i.e. children
aged 10–11 years)2.
Children living in the most deprived areas in England are twice as
likely to have obesity as those in the least deprived, with this gap
widening over time3.
Childhood
obesity is defined using body mass index (BMI), adjusted for age and
sex. BMI provides a practical estimate of body fat in children and young
people; however, it is not a direct measure of adiposity and should be
interpreted with caution4,5.
Assessing the BMI of children is more complicated than for adults,
owing to changes to BMI as they grow and mature. In addition, there are
different growth patterns seen in boys and girls5. A BMI at or above the 91st centile indicates overweight, while a BMI at or above the 98th centile indicates obesity6. The
Royal College of Paediatrics and Child Health (RCPCH) BMI chart or
World Health Organization growth charts can be used to determine centile
placement6.
Obesity alters drug absorption, distribution, metabolism and excretion7,8. These
physiological changes increase the risk of both subtherapeutic
treatment and adverse drug reactions if standard weight-based dosing is
used without appropriate adjustment. However, many commonly used
references, such as British National Formulary for Children (BNFC)9
and summary of product characteristics (SPCs), do not provide dosing
guidance for weight extremes, contributing to potential variability in
prescribing.
Pharmacists and other healthcare professionals have
an important role in optimising medicines use in children with obesity.
This article provides a practical overview of the evidence and
considerations regarding safe prescribing, with examples of commonly
affected medicines, guidance on weight-based calculations and strategies
to reduce harm.
Obesity
causes important alterations in physiology, such as changes in tissue
composition, increased circulating blood volume and cardiac output,
altered regional flow distribution, and impaired liver and kidney
function10. All
of these physiological alterations can affect pharmacokinetic (PK)
parameters, including drug absorption, volume of distribution (Vd),
metabolism and elimination11. As
a result, the physiochemical properties of a drug, such as lipid
solubility or relative protein binding, might have different effects on
drug PK in obese children compared with non-obese children10.
The role of pharmacists
Pharmacists play an important role in ensuring dosing decisions for children with obesity are appropriate and evidence-based.
Pharmacists can support safe prescribing by:
- Reviewing prescriptions for medicines where dosing is affected by weight;
- Advising on the most appropriate weight measure to use (e.g. AdjBW may be more suitable for certain medicines)19;
- Highlighting when therapeutic drug monitoring is required and helping interpret results where pharmacokinetics may be altered20;
- Encouraging clear documentation of weight, height and BMI in the patient’s medical record4.
In
complex cases, involving the local medicines information team or
paediatric pharmacy specialists may be necessary to ensure safe and
effective treatment.
Medicines that contribute to weight gain
Some
medicines commonly prescribed in childhood are associated with weight
gain. In children already living with obesity, certain medicines may
worsen existing health problems and increase the risk of future
complications, including insulin resistance and cardiovascular disease21.
Medicines known to affect weight include:
- Corticosteroids:
for the treatment of conditions such as asthma, nephrotic syndrome, and
autoimmune diseases. Long-term use can lead to increased appetite,
alter fat distribution and contribute to metabolic changes22;
- Antipsychotics:
second-generation antipsychotics (e.g. risperidone, olanzapine) are
associated with rapid and significant weight gain, even after short-term
use23;
- Antidepressants: some also contribute to weight gain24.
Pharmacists should support prescribers and families in balancing the benefits and risks of treatment. This includes:
- Identifying alternative medicines with lower risks;
- Recommending baseline and follow-up monitoring of BMI, blood glucose and lipids, in line with national and local guidance;
- Discussing non-pharmacological interventions, where clinically appropriate;
- Regular medication reviews, including deprescribing, where appropriate.
Best practice tips for pharmacists
- Review
dosing carefully for medicines affected by obesity, such as
antibiotics, antiepileptics, chemotherapy agents and psychotropics;
- Ensure accurate recording of weight, height and body mass index, where appropriate, to support safe prescribing;
- Use
up-to-date, authoritative sources such as the BNFC, the UK Medicines
Information/Neonatal and Paediatric Pharmacists Group Q&A on
childhood obesity dosing, relevant summary of product characteristics,
National Institute for Health and Care Excellence guidelines and
specialist pharmacy support to inform dosing decisions;
- Identify
medicines that contribute to weight gain, discuss risks and benefits,
and support deprescribing or alternative therapies when appropriate;
- Use respectful, non-judgemental language focused on health, avoiding weight stigma in conversations with children and families;
- Recognise when safeguarding concerns arise and escalate them by following local safeguarding procedures;
- Collaborate with the multidisciplinary team and specialist pharmacists to optimise medicines management in complex cases;
- Provide clear advice to families on medication use, side effects and when to seek further help.
https://pharmaceutical-journal.com/article/ld/medication-related-considerations-in-childhood-obesity
