A Canadian doctor and researcher is sounding a warning about the "inactive" ingredients in common over-the-counter medications and prescription medications. He thinks that the inconsistency of formulation and lack of labelling of these ingredients could be a problem for people who have sensitivities or allergies to some of the inactive ingredients that are used in medications.

Dr. Giovanni Traverso, an assistant professor from Brigham and Women's Hospital, Harvard Medical School, and the Department of Mechanical Engineering at M.I.T. in Boston, led a study investigating the inactive ingredients in medications. His findings suggest these inactive ingredients can play a very active role in triggering irritation and even allergic reactions in some people.

Traverso told Quirks & Quarks host Bob McDonald he has first-hand experience with this.

"We had a patient suffering from celiac disease who had been prescribed omeprazole, which is a common medication used for acid reflux as well as ulcer treatment. The drug that the patient picked up had wheat starch, and that's where the gluten comes from and that really makes the symptoms associated with celiac disease worse."

This study looked at 38 critical inactive ingredients in pills and capsules that could be of concern to patients with allergies or sensitivities (U.S. FDA)

Inactive ingredients in medications

All pills and capsules contain two components. One is the active ingredient, which is the drug intended to provide the desired pharmaceutical effect, whether it be a pain reliever or an antibiotic or an antidepressent. The other component is the inactive ingredients that are added for a variety of reasons, all of which are important, according to Traverso.

"They can facilitate absorption of the drug, they can improve the stability of the drug and so also enhance the shelf life, they can help modulate or perhaps shield the taste of the drug, they can also affect the appearance and they also help control how the drug is released from the actual pill or capsule."

Traverso's study looked at a range of medications to investigate how much of the capsule or pill was made up of the inactive ingredient, and how many of these ingredients there were.

His team found that up to 75 per cent of some medications consisted of these inactive ingredients. They also found that there were anywhere from eight to as many as 30 different inactive ingredients in a given medication. They identified about 1,000 different inactive ingredients across the drugs they looked at.

Most of these ingredients would be considered harmless. They found food additives like sugars, cornstarch and gelatin. One of the most common ingredients was cellulose and they also found a range of polymers and dyes. They also found a range of additives that might not be quite so harmless to some people.

Not so 'inactive' ingredients

The study found about 38 inactive ingredients that might be of concern. These included things like gluten, peanut oil and various chemical dyes, which can trigger allergic reactions or sensitivities in some people. Others may experience an intolerance to an inactive ingredient that results in malabsorption of the drug and consequent gastrointestinal issues.

Traverso says lactose is an excellent example. It's a sugar to which many people are intolerant. "About 50 per cent or so of all pills and medications have lactose in them. And usually at the levels that are present in a single pill or capsule, that's not going to have much of an effect. But if someone is taking many pills or capsules it may manifest in adverse symptoms whether it be gastrointestinal upset, bloating or loose stools for example."

At this point, many doctors may not be aware of which of these inactive ingredients are in the drugs they prescribe to their patients. This can be because there are many different formulas for a given medication, and those formulas can vary depending on when the drug was manufactured. Information is generally available on these formulations on websites or in the fine print in inserts that come with some drugs, but few take the time and trouble to seek out that information.

Video provided by Dr. Traverso's Lab:

Raising awareness

Traverso wants to boost awareness of the risks that inactive ingredients in drugs could pose to vulnerable people. His hope is that pharmaceutical companies provide more information to doctors, and that alternative drug formulas can be developed for people with allergies or sensitivities. He said it is also important for patients to understand that a given drug formula can change over time.

"When someone has been on a drug for a very long time and then they are switched to a different version of the same drug, same dose and then they start noticing side effects, it's important to consider the differences between the two formulas," he said.

"The drug may be exactly the same but the inactive ingredients may be very different."