Introduction

Children with obesity are at risk of overdose  if total body weight (TBW) is used inappropriately during weight-based dose calculations.1–3 Potentially serious toxic effects include opioid-induced respiratory depression, paracetamol-induced hepatic injury and antibiotic-induced renal injury. Such drugs are routinely prescribed by very junior medical staff, who may be unaware of the risks of overdose when using TBW to calculate drug doses.

Inadvertent drug overdose is just one of several risks faced by children with obesity during hospital admission. They are twice as likely as healthy weight children to experience life-threatening airway and breathing-related complications during anaesthesia and the perioperative period. They may have increased length of stay, and they are more likely to undergo certain types of surgery such as tonsillectomy. Coexisting conditions can complicate drug effects such as sleep apnoea and non-alcoholic fatty liver disease.4 5

Therapeutic failure can result from underdosing if dose reduction is inappropriately performed using ideal body weight (IBW), guesswork or age-based dosing.2 6 IBW can be a much lower value than an obese child’s actual weight, and the dosing of many drugs requires an adjustment above IBW as a result of the additional fat and lean mass that develops in obesity. Size descriptors that are between IBW and TBW, such as lean body mass (LBM) or adjusted body weight (ABW), are often more appropriate.1 2

The dose adjustment methods recommended in obesity are complex and time consuming. This is an important potential barrier to safe dose calculation and may explain why confusion and a ‘best guess’ approach is observed in clinical practice. Clinicians with some awareness of …