Overlooked Ingredients In Medicines Can Sometimes Trigger Side Effects

If you have a bad reaction to a medicine, it might not be the drug itself, but what are called "inactive ingredients" in the pill or capsule.

An article published Wednesday in Science Translational Medicine surveys this field and finds ingredients that are potentially troublesome for some people are ubiquitous.

For example, a few years ago study co-author Giovanni Traverso, a gastroenterologist at Harvard-affiliated Brigham and Women's Hospital, came across a patient with a severe gluten intolerance called celiac disease. The person was having trouble with a medication that apparently contained gluten as an inactive ingredient — potentially making the condition worse, not better.

Traverso, who is also a biomedical engineer with an appointment at MIT, started exploring this topic with some colleagues by weighing pills in the hospital pharmacy. They concluded that, on average, about 75 percent of a pill or capsule is made up of inactive ingredients – that is, material other than the chemical or chemicals that determine the therapeutic effect of a drug.

In their article, the scientists say drug companies have more than a thousand of these inactive constituents to choose from. "In some instances there can be up to 35 of them in a single pill," Traverso says in an interview.