Medication-related considerations in childhood obesity

A practical overview of the evidence and considerations regarding safe prescribing for children with obesity, with examples of commonly affected medicines

#obesity #paediatrichealth #weightloss #childhoodobesity

 

 

 

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 2022^​1​. 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 time^​3​.

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 caution^​4,5​. 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 girls^​5​. A BMI at or above the 91st centile indicates overweight, while a BMI at or above the 98th centile indicates obesity^​6​. The Royal College of Paediatrics and Child Health (RCPCH) BMI chart or World Health Organization growth charts can be used to determine centile placement^​6​.

Obesity alters drug absorption, distribution, metabolism and excretion^​7,8​. 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.

How obesity affects drug distribution, metabolism and clearance in children

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 function^​10​. All of these physiological alterations can affect pharmacokinetic (PK) parameters, including drug absorption, volume of distribution (Vd), metabolism and elimination^​11​. 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 children^​10​.

 

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 altered^​20​
  20.

  Deswal P, Singh MF, Setya S. Critical Contribution of Pharmacists in Optimising Medication Safety among Children: A Narrative Review. JCDR. Published online April 1, 2025. doi:10.7860/jcdr/2025/75234.20814
  ;
• Encouraging clear documentation of weight, height and BMI in the patient’s medical record^​4​.

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 disease^​21​.

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 changes^​22​;
• Antipsychotics: second-generation antipsychotics (e.g. risperidone, olanzapine) are associated with rapid and significant weight gain, even after short-term use^​23​;
• Antidepressants: some also contribute to weight gain^​24​.

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