Drug Side Effects Can Come From Inactive Ingredients : Shots - Health News Drugmakers add inactive ingredients to stabilize medications and sometimes to help the body absorb the active ingredients. But the inactive constituents can cause side effects in rare cases.

Overlooked Ingredients In Medicines Can Sometimes Trigger Side Effects

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If you have a bad reaction to a medicine, it might not be to the drug itself but to other ingredients in the pill or capsule. An article in Science Translational Medicine examined the issue and finds that the average oral medication contains eight inactive ingredients. NPR science correspondent Richard Harris reports.

RICHARD HARRIS, BYLINE: A few years ago, Harvard gastroenterologist Giovanni Traverso 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 person's condition worse, not better. Traverso got intrigued and found that the typical pill is more inactive ingredient than actual drug.

GIOVANNI TRAVERSO: It's somewhere around 75 percent of the actual, you know, pill or capsule is actually taken up by these inactive ingredients.

HARRIS: And drug companies have more than a thousand to choose from. They can include materials like gluten and lactose and dyes that can trigger allergies.

TRAVERSO: In some instances, there can be up to 35 of them in a single pill.

HARRIS: He says these inactive ingredients are essential to stabilize medications and sometimes to help the body absorb the actual drug. People taking multiple medicines can end up getting the same inactive ingredient from several pills and get an unexpectedly large dose. Say you are lactose intolerant and take a pill that uses lactose sugar as an inactive ingredient.

TRAVERSO: It's probably not going to manifest in any significant symptoms. But as the number of pills that you're taking - then certainly you might cross that threshold.

HARRIS: One challenge and understanding the scope of this problem is it's often not clear how much of a particular substance it takes to trigger an allergy or other reaction.

TRAVERSO: You know, and it's something that might vary from one person to another. But, you know, for a lot of these sugars and other ingredients, we don't really know today.

HARRIS: In San Diego, John Kelso, an allergist at the Scripps Clinic, says he occasionally comes across patients who have had an allergic reaction to something in their medications.

JOHN KELSO: It's actually, we think, quite uncommon.

HARRIS: In fact, most of the time, it's a false alarm. For example, after many years worrying about the traces of egg protein in flu vaccines, health officials now say that people with egg allergies are not at risk from the shot. Overreaction to this worry can actually backfire.

KELSO: And oftentimes the medications are being withheld from patients who say they're allergic to eggs or soy and - or something else that may be in the medication. But it's actually not a problem.

HARRIS: In fact, one of the most common allergies to an actual drug, penicillin, is itself overstated, Kelso says.

KELSO: We've realized lately that approximately 95 percent of patients who are labeled as being penicillin allergic are not either because they never were or because they had an allergy that waned with the passage of time.

HARRIS: For people who are concerned about the inactive ingredients, Traverso at Harvard says it is possible to track down that information in the fine print that comes with pills.

TRAVERSO: One can look in the inserts of medications. And then, you know, you can look through all the texts, and eventually you'll find it.

HARRIS: The National Library of Medicine also has an online database called Pillbox. Traverso and his colleagues have a patent pending on an algorithm that can help make this sleuthing easier. They're thinking about developing a consumer app or some software to help doctors and pharmacists alert their patients to potentially troublesome inactive ingredients. Richard Harris, NPR News.

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