Oral forms of medications include inactive ingredients to help stabilize the drug or aid in its absorption. While these components are usually harmless, nearly all of these pills contain some ingredients that can cause allergic reactions, a new study published in Science Translational Medicine found.
Researchers from the Massachusetts Institute of Technology in Cambridge, Mass.; Brigham and Women's Hospital in Boston; and Harvard Medical School in Boston, set out to determine how "inactive" these ingredients are.
Researchers found that on average 75 percent of a pill or capsule was made up of inactive ingredients, and some of the pills had as many as 35 inactive compounds.
Drugmakers can choose to add thousands of compounds into their drugs, including things like gluten, lactose and dyes.
The researchers found that 38 ingredients have been associated with a very specific allergic reaction, and about 90 percent of pills have at least one of those ingredients.
Generally, the amounts in any given pill may not be enough to trigger an allergy, but a subset of patients may be incredibly sensitive and develop symptoms. In addition, when patients take multiple medicines with the same inactive ingredients, the doses can add up.
"I don't want to malign inactive ingredients in any way," study co-author Giovanni Traverso, MD, a gastroenterologist at Brigham and Women's Hospital, told NPR. "I think inactive ingredients are very helpful."
However, because there are many formulations of drugs, physicians don't often know what ingredients are in a specific pill they prescribe.
While allergic reactions to inactive ingredients are rare, the study authors hope their research will underscore "the need to maximize the tolerability and safety of medications and their inactive ingredients."