New guidelines published on antibiotic dosing for people living with obesity

A major new systematic review has been published providing much-needed guidance on how obesity affects the way antibiotics are processed in the body – and how dosing should be adjusted to ensure effectiveness.

Titled “The pharmacokinetics of antibiotics in patients with obesity: a systematic review and consensus guidelines for dose adjustments”, the study, led by Anne-Grete Märtson, PhD and a team of international experts, reviewed data from 128 studies to assess how obesity influences the pharmacokinetics (how drugs are absorbed, distributed, metabolised, and excreted) of commonly used antibiotics.

The review examined over 6,000 studies, narrowing down to 128 with relevant data on adult patients (aged 18+) with a BMI over 30 kg/m². The research showed that obesity can alter the body’s response to certain antibiotics, potentially leading to suboptimal drug levels and reduced treatment effectiveness.

The most commonly studied antibiotics were β-lactams, with 57 studies reviewed. The authors found that although obesity modestly alters the pharmacokinetics of β-lactams, current evidence does not support routine dose adjustments for this class of drugs. However, the impact of obesity was more pronounced for aminoglycosides and glycopeptides, leading the authors to recommend weight-based dosing for these antibiotic groups.

Due to the variability across study populations and methodologies, a meta-analysis was not possible, and the overall certainty of evidence was deemed low or very low across all antibiotic classes. The review highlights significant gaps in the current research and calls for more high-quality studies in this area.

In the meantime, the authors recommend the use of therapeutic drug monitoring to guide individualised dosing when treating people living with obesity, particularly when using antibiotics with narrow therapeutic windows or those affected most by body composition.

This important review offers a foundation for clinicians to optimise antibiotic treatment in people living with obesity and marks a step forward in addressing an under-researched area of clinical pharmacology.