Traditionally, children are dosed according to their body-weight or age, as a surrogate of ‘normal’ size and function. However,pharmacokinetic (PK) alterations occur in obesity due to changes in body composition and physiology. It is important to consider the consequences of these changes as failure to adjust doses appropriately in patients who are obese may result in therapeutic failure or drug-related toxicity. This document outlines the key factors for consideration and provides dosing recommendations for a limited list of medicines.

The recommendations need to be seen in the context of the limited published data available on drug dosing in children living with obesity.  Some of the information has been derived from adult obesity data. It is intended to generate discussion and for paediatric teams to agree a consensus locally. The list is not exhaustive and absence does not imply that no dose adjustment is needed in children who are obese. Patient-specific factors such as underlying organ function, illness severity and extent of obesity should be taken in to account when determining appropriate drug doses for individual patients. Drug levels should be monitored wherever possible.

In all cases, treatment should not rely purely on calculated dose but be clinically reviewed regularly to ensure that the child is receiving the correct dose in terms of both efficacy and safety.

Due to the potential for differences in drug handling and pharmacokinetics in infants and neonates, this information does not apply to children under the age of 2.

Keywords: obese obesity dosing overweight pharmacokinetics weight BMI IBW