Q: I’ve heard that Pepto-Bismol can be taken to prevent traveler’s diarrhea, not just to treat it. Should I try this?
A: It’s something worth considering if you are traveling to a developing country, especially if you have a history of traveler’s diarrhea or are at risk from complications due to a medical condition you have. But talk with your health care provider first, since there are some caveats and contraindications.
The active ingredient in Pepto-Bismol is bismuth subsalicylate (BSS, available also generically), which has antimicrobial and anti-inflammatory effects. The typical recommendation is to take two tablets with each meal and two at bedtime (a total daily dose of 8 tablets), starting with the first meal at your destination and ending with your last meal (to be extra safe, you can take one more dose after that, which might be on the plane home). This has been shown to reduce the risk of traveler’s diarrhea by up to 65 percent. Chewable tablets or caplets (as opposed to liquid versions) are most convenient for traveling.
A harmless and temporary side effect is darkening of stool and the tongue. To prevent your tongue turning black, rinse your mouth thoroughly after chewing the tablets or, better yet, gently brush your tongue, especially after the nighttime dose. A problem with having black stools is that this could indicate gastrointestinal bleeding, something that a number of travel-related diseases produce, so taking BSS could interfere with its detection.
Other potential side effects include constipation (which some people might consider worse than getting diarrhea) and, rarely, mild and transient tinnitus (ringing in the ears), which can also happen with aspirin, another salicylate drug.
Other things to be aware of before popping these pink pills:
- It’s generally cautioned that BSS not be taken longer than three or four weeks because there have been a few reported cases of bismuth toxicity, characterized by tremors and other neurological symptoms. A study from 1990 found that taking 12 tablets a day for 6 weeks did not have toxic effects, however. In any case, most people don’t travel long enough for bismuth toxicity to be a concern. Of greater concern is salicylate toxicity in people who concomitantly take BSS and aspirin—or who take it while also over-applying salicylate-containing liniments, such as Bengay (in the oil of wintergreen). The amount of salicylates you absorb from 8 tablets of BSS is equivalent to that of 3 or 4 adult aspirins.
- BSS can interact with many drugs, including doxycycline, which, depending on your destination, may be recommended for malaria prevention. If you take both doxycycline and BSS on your travels, you should take them a few hours apart.
- People with certain medical conditions, including (but not limited to) inflammatory bowel disease, should not take BSS. Children under 3 should not take BSS. Consult your doctor before giving it to children between the ages of 3 and 12. It should not be taken by anyone who is allergic or sensitive to aspirin.
- BSS is not a substitute for being careful about what and where you eat and drink when you travel to developing countries. You should still generally avoid tap water (and even bottled water without a proper seal), unpeeled raw fruits and vegetables, salads, unpasteurized dairy foods, undercooked meats and shellfish, and street foods.
- Rather than recommend BSS prophylactically, some doctors advise that travelers bring the anti-diarrheal drug loperamide (available by prescription or over the counter, as in Immodium) and antibiotics with them to use only if they become very sick.