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Obesity can significantly alter the way medications behave in the body, impacting both safety and efficacy. However, drug labels often fail to mention these critical differences, leaving healthcare professionals without essential guidance for treating patients with obesity.
Experts in obesity and pharmacology are raising awareness about this issue, given that obesity affects 42% of U.S. adults. Some drugs remain in the body longer in people with obesity, increasing the risk of drug-drug interactions, while others may be less effective due to lower concentrations in plasma and tissues.
Medications Affected by Obesity
Examples of medications influenced by obesity include:
- Posaconazole (Noxafil) – An antifungal drug with a longer half-life in people with obesity, increasing the risk of drug interactions.
- Cefazolin – An antibiotic that may not reach effective concentrations in patients with obesity, potentially leading to undertreatment.
- Brexpiprazole (Rexulti) – An antipsychotic that takes longer to reach effective levels in people with obesity.
- Levonorgestrel (Plan B) – An emergency contraceptive that is less effective in individuals weighing over 70 kg.
- Ibuprofen (Advil) – A commonly used anti-inflammatory drug that clears from the body more rapidly in individuals with obesity, potentially requiring higher doses.
The Need for Labeling Changes
Obesity is rarely considered a “special population” in drug labeling, despite its prevalence. In contrast, individuals with chronic kidney or liver disease—who make up a smaller percentage of the population—often have specific dosing recommendations in drug labels.
The U.S. Food and Drug Administration (FDA) has acknowledged the issue and held a workshop in 2022 to explore the impact of obesity on drug safety and efficacy. However, there is currently no requirement for pharmaceutical companies to update labels for drugs already on the market.
Impact on Cancer Treatment
At the Obesity Week conference in November 2024, Harvard obesity expert Dr. Caroline Apovian highlighted the dangers of inadequate drug labeling. A survey of oncologists revealed that less than half were aware of the extended half-life of posaconazole in patients with obesity, a factor that can compromise chemotherapy effectiveness.
“When we know better, we should do better,” said Theodore K. Kyle, a leading pharmacologist and obesity advocate. Experts are urging the FDA to mandate labeling updates to reflect these crucial considerations.
Actionable Changes for Dosing in Obesity
Researchers have suggested alternative dosing strategies for affected drugs, including increasing the initial dose for some medications, extending washout periods, and recommending alternative treatments when necessary.
As awareness grows, experts hope that drug manufacturers and regulatory agencies will take necessary steps to improve labeling, ensuring that patients with obesity receive optimal and safe treatment.
Disclaimer: This article is for informational purposes only and should not be considered medical advice. Patients should consult their healthcare providers before making any changes to their medication regimen.
