Obesity can affect responses to medicines and treatments

BYLINE: MaryAnne Hochadel PharmD, BCPS

Obesity is a recognized health crisis that has numerous implications for public health. As a pharmacist, I am all too familiar with the health problems that arise in patients from being overweight, including increased risks for high blood pressure, diabetes, heart disease, joint problems, and certain cancers. During this pandemic, we have all become aware that those who are significantly overweight have risks for poor outcomes due to COVID-19. Obesity impacts more than just health status. It also can affect responses to medicines and treatments. Many health care professionals are aware that certain medications are dosed by body weight. Obesity adds complexities to dosing medications beyond having to consider the additional weight of the individual. Obesity results in alterations to body composition and physiology that can affect drug disposition into tissues, organ processing, and elimination, possibly leading to therapeutic failure or toxicity.

Examples of medications that we know require special care in the obese patient include, but are not limited to, certain antibiotics (examples: vancomycin, aminoglycosides), anesthetics used in surgery, anticoagulants (“blood thinners”), and cancer treatments. For birth control, it has been demonstrated that some combination hormonal contraceptive products have reduced efficacy in obese female patients above a certain body mass index (BMI) threshold; such products should not be used in these patients to prevent pregnancy.

While we have made progress in understanding how obesity affects organ function, tissue penetration, and elimination of medications in the past few decades, there is still much research to be done. For the vast majority of medications, there are few studies to know the impact of obesity on the success of those treatments.

We still have so many questions. How does obesity affect the immune response to vaccination? Some studies with specific vaccines indicate that metabolic changes due to obesity may impact the development of proper immunization response. Do obese patients have less treatment success with a certain antibiotic due to poor tissue penetration at the sites of infections? Is a biologic injectable drug for asthma less effective in patients over 150 kg for whom drug-dosing data are insufficient? Do obese children have different risks than obese adults with a certain medication? These are but a few examples. Answering these questions is important, particularly in light of the rising incidence of obesity globally.

Ultimately, our best offense is likely a good defense – to help reduce the impact of obesity on disease and treatment variations. We all need to be encouraged to maintain a proper body weight, not only to prevent risk of disease, but also to help ensure the best treatment outcomes when health concerns arise.