The active ingredient in Pepto Bismol, bismuth subsalicylate, is often used to treat and prevent diarrhea while traveling — but a new study found it may not help with prevention. 

from the Centers for Disease Control and Prevention, "no significant difference" was found for symptoms of loose stool or diarrhea between groups who took the medication for prevention and those who took a placebo.  

Since 1939, bismuth subsalicylate has been approved by the Food and Drug Administration for the treatment of diarrhea, heartburn, indigestion, nausea and upset stomach. But, as the authors note, it's also used off-label for the prevention of diarrhea, especially among international travelers.

The study issued questionnaires before, during and after travel to the 270 participants, who had a median age of 32 and planned to travel to Southeast Asia, south central Asia, North Africa or sub-Saharan Africa for 7 to 21 days. Participants were recruited from clinical sites in New York in Massachusetts.

The group given the medication took 4 tablets twice daily during their trip. 

The study did have limitations, including not reaching the target sample size. But it did provide the first new data since the 1980s on the potential use of bismuth subsalicylate in diarrhea prevention, according to the study's authors. 

"Despite this study not reaching the targeted sample size, there are nonetheless important considerations for healthcare providers conducting pretravel consultations for international travelers," the authors wrote.

The authors also noted further studies are needed to determine if there is a benefit in certain traveler groups or under certain circumstances. 

"A larger study might show benefit, although the benefit may be small given the results of this study," they wrote. 

Procter & Gamble, the parent company of Pepto Bismol, provided the medication for the study but did not participate in any procedures, the authors noted.