People’s Pharmacy | Will Pepto-Bismol prevent traveler’s diarrhea?

Q. While in Morocco eight years ago, my entire group of 12 travelers ended up with diarrhea. It went through our group in waves. Our group leader put each sick one on “the diet”–Coca-Cola (not diet), bananas and dry cooked rice. I had a prescription for Cipro, which I took, but my roommate seemed to do equally well with Pepto-Bismol. The diet also seemed to help.

A. Traveler’s diarrhea is a common problem for people traveling in places where they may be exposed to contaminated water or food. Coca-Cola might be a way to replenish some electrolytes as well as fluids if a beverage like Gatorade or Pedialyte were not readily available.

Pepto-Bismol is recommended not only to treat symptoms, but also to prevent the onset of diarrhea. A double-blind trial comparing four tablets twice daily to placebo, however, did not result in a significant difference in diarrhea symptoms among travelers (Journal of Travel Medicine, Oct. 1, 2025). Pepto-Bismol may cause black stool or tongue and should be avoided by people allergic to aspirin.

Some infectious disease experts are starting to question the use of antibiotics such as ciprofloxacin unless the diarrhea is incapacitating (Travel Medicine and Infectious Disease, Jan-Feb. 2019). Besides contributing to microbe resistance, ciprofloxacin may cause tendon rupture, peripheral neuropathy or psychiatric reactions.

Q. I know that many people are using water filters to eliminate impurities. They may not realize that reverse osmosis water filters remove magnesium and other minerals.

Most people don’t understand that magnesium is essential for proper vitamin D metabolism. They may need to take magnesium supplements along with vitamin D to maintain good health.

A. Not all home water filters use reverse osmosis, but those that do are effective at removing minerals, including magnesium. You are correct that vitamin D and magnesium work together in the body. According to scientists, “taking large doses of vitamin D can induce severe depletion of Mg [magnesium]” (American Journal of Therapeutics, Jan-Feb. 2019).

People often think of vitamin D as essential only for strong bones, but it is crucial for many other aspects of health. One exciting new study found that middle-aged people with higher levels of vitamin D became seniors with lower levels of toxic tau in their brains (Neurology Open Access, April 1, 2026). The Framingham Heart Study Generation 3 Cohort provided the long-term data on nearly 800 individuals.

The researchers conclude, “Low vitamin D in midlife may represent a potentially modifiable target to mitigate the risk of neuroimaging signs of preclinical dementia.” In short, keeping vitamin D levels up may reduce your risk of dementia later in life.

To learn more about this vitamin that also acts as a hormone, you may wish to read our eGuide to Vitamin D and Optimal Health. You can find this online resource under the Health eGuides tab at www.PeoplesPharmacy.com.

Q. My doctor recently prescribed a beta blocker heart medicine called metoprolol. Within a week I started having crazy nightmares. Last night I dreamed I was being suffocated by my husband and woke up to the sound of my screaming. I scratched him in my panic. Could metoprolol do that?

A. Beta blockers such as metoprolol and propranolol have been linked to “distressing, recurrent nightmares” (Case Reports in Neurological Medicine, Jan. 5, 2026). Don’t stop such a drug suddenly, as it could trigger heart problems. Perhaps your doctor could consider a different medication.

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In their column, Joe and Teresa Graedon answer letters from readers. Write to them in care of this newspaper or e-mail them via their Web site: www.peoplespharmacy.com. Their newest book is Top Screwups Doctors Make and How to Avoid Them (Crown).

This story was originally published April 19, 2026 at 1:00 AM with the headline "People’s Pharmacy | Will Pepto-Bismol prevent traveler’s diarrhea?."