Alongside the active components in medicines, there is almost always a list of other ingredients.

Manufacturers add these inactive components for a number of reasons. For instance, they might make the drug more easy to absorb or stabilize the compound.

Or, they could simply enhance the way the product looks or tastes.

For the majority of people, additives such as fructose and lactose will do no harm whatsoever, but for certain people, they could cause issues.

Recently, a group of researchers from the Massachusetts Institute of Technology in Cambridge and Brigham and Women’s Hospital in Boston, MA, decided to investigate these additives.

They wanted to understand whether these ingredients might be affecting people’s health.

An unexpected reaction

Giovanni Traverso, the study’s senior author, began looking at this topic around 5 years ago. An experience that he had while treating one of his patients with celiac disease piqued his interest.

He prescribed the individual a common acid suppressant called omeprazole. Although many people take this drug and generally tolerate it well, Traverso’s patient responded poorly.

Within a week, the patient reported feeling sick. On further investigation, Traverso found that the particular formulation that the patient had taken included ingredients derived from wheat products, which could contain gluten.

That really brought it home to me as far as how little we know about tablets and the potential adverse effects they might have. I think there’s a tremendous underappreciation of the potential impact that inactive ingredients may have.”

Assistant professor and gastroenterologist Giovanni Traverso

As it stands, we do not know how often this type of reaction might occur. Daniel Reker, one of the lead authors of the study, says:

“For most patients, it doesn’t matter if there’s a little bit of lactose, a little bit of fructose, or some starch in there. However, there is a subpopulation of patients, currently of unknown size, that will be extremely sensitive to those and develop symptoms triggered by the inactive ingredients.”

Hidden compounds

When a doctor prescribes a drug to someone, they take careful note of the active compound and the dosage, but they are much less likely to think about the inactive ingredients.

Even drugs with the same active chemical at the same dosage can have different ingredients, depending on who manufactured them. For instance, the authors note that 43 different companies produce a total of 140 distinct formulations of levothyroxine, a treatment for thyroid hormone deficiency.

Also, although manufacturers provide a list of ingredients on the packet, it might not be clear from the chemical names which of them could contain allergens. For instance, the packet would not label a wheat derivative as containing gluten.

Most people will only consume small quantities of these inactive ingredients, but some groups, such as older adults, tend to take more medications. The authors write:

“A patient taking 10 prescription medications each day would ingest an average of 2.8 [grams] of inactive ingredients daily.”

Medical professionals know little about this subject, so the researchers set out to fill in some gaps. The scientists published their findings earlier this week in the journal Science Translational Medicine.