Why a medicine works for one person but not another: Gastroenterologist says the answer may lie in the gut

The gut 's influence is widely discussed in health circles. Its bidirectional pathways, such as the gut-brain and gut-immune axes, show how extensively it can influence different systems in the body. Its role may even help determine how well a medicine works. ALSO READ: Can you eat the same breakfast every day? Gastroentrologist says it may ‘change’ your gut health

You may have noticed that the same medicine can work differently from one person to another, and the gut could be one of the factors behind these varying responses. Dr Ramesh Garg, Senior Director and HOD of Gastroenterology at Fortis Hospital, Shalimar Bagh, weighed in on this, confirming that the gut can influence how medicines are absorbed and metabolised, potentially affecting their effectiveness and side effects.

The reason behind the gut's far-reaching influence is simple. As Dr Garg explained, it is much more than a digestive organ. "Gut is a complex biological system containing trillions of microorganisms, a highly active immune system, an extensive nervous network, and a large surface area that constantly interacts with food, drugs, and the environment.”

Because of this complexity, he stated that understanding the gut can provide clues about how a medicine works and why people may respond differently to the same treatment.

What happens after you swallow an oral medicine? The first place of reaction is the gut. Dr Garg described the interaction: “The intestinal lining determines how much of the drug is absorbed, while enzymes and transport proteins can modify or transport the drug. Therefore, changes in absorption, metabolism, or transport can influence both the effectiveness and side effects of a treatment.”

So, the gut is instrumental in deciding how much of the drug enters the body and how it is processed. Now, because of differences in these functions, the treatment may different and even side effects.

The gut microbiome imparts another layer to this context. Dr Garg said, “ Intestinal bacteria can metabolize medicines, sometimes converting them into active or inactive compounds.”

The relationship is bidirectional. Gut bacteria can change how a medicine works, and medicine can also alter the microbial community.

In the end, the expert reiterated that the gut acts as a biological ‘sensor' of drug action. Understanding its interaction with medicines, microbes, and the immune system can help researchers really evaluate how a drug works, why and how it works, and who may benefit. This answers the common doubt why the same medicine works differently for different people.

Note to readers: This article is for informational purposes only and not a substitute for professional medical advice. Always seek the advice of your doctor with any questions about a medical condition.

Adrija Dey’s proclivity for observation fuels her storytelling instinct. As a lifestyle journalist, she crafts compelling, relatable narratives across diverse touchpoints of the human experience, including wellness, mental health, relationships, interior design, home decor, food, travel, and fashion that gently nudge readers toward living a little better.