The Antibiotics Most Likely to Cause Diarrhea

Antibiotics treat minor and more significant bacterial infections. While effective (and, in some cases, lifesaving), they can have some unintended negative effects—including diarrhea, which can be severe. If you've had this problem or are hoping to avoid it, knowing which drugs are most likely to cause diarrhea can help you and your doctor decide which treatment is best for you the next time you need antibiotics.

Why Antibiotics Cause Diarrhea

Your body harbors friendly bacteria on your skin and throughout your digestive tract. For the most part, these bacteria are beneficial, assisting in digesting and processing nutrients from food. They also provide a barrier to overgrowth or infection by bacteria that may cause illness.

When you have a bacterial infection (such as strep throat or a urinary tract infection), your doctor may prescribe an antibiotic to kill the pathogen causing the illness. But antibiotics act throughout your body and may kill both the bacteria that keeps you healthy and that which causes illness.

That alters the way your intestine handles nutrients and fluids, and changes its motility (the way it contracts to move material through). When that happens, many people develop diarrhea. In most cases, this diarrhea will be mild and will clear up quickly once you have ended your course of antibiotics.

C difficile-Associated Diarrhea

In a small number of people (1% to 3% of healthy adults), a bacteria called Clostridium difficile (C difficile or C diff) lives in the colon.

In a minority of those people, C difficile may begin to multiply and take over the colon after taking a course of antibiotics. This can, unfortunately, result in C difficile-associated diarrhea (also called pseudomembranous colitis).

In rare cases, this may also be associated with toxic megacolon, which is a life-threatening surgical emergency.

Antibiotics Most Likely to Cause Diarrhea

While any antibiotic can result in either mild diarrhea or C difficile colitis, some have a higher risk of doing so than others. The antibiotics formulated to kill a wide variety of bacteria (both the good and the bad) are more likely to have this effect.

Most associated with C. difficile colitis:

• Lincosamides (e.g., clindamycin)
• Monobactams (e.g,. aztreonam)
• Cephalosporins (e.g., ceftriaxone, cefotaxime)
• Fluoroquinolones (e.g., ciprofloxacin, norfloxacin, ofloxacin)
• Carbapenems (e.g., doripenem, ertapenem)

Moderate amount of risk:

• Penicillins (e.g., penicillin G, ampicillin)
• Imipenem
• Macrolides (e.g., erythromycin, azithromycin)
• Sulfa-trimethoprim

Lowest risk:

• Aminoglycosides (e.g., amikacin, gentamicin, streptomycin, tobramycin)
• Metronidazole
• Nitrofurantoin

Tetracycline has shown no increased risk of diarrhea.

Probiotics for Prevention

Probiotics are live cultures of friendly bacteria. Research suggests that taking probiotics, which contain and can help restore healthy gut bacteria, can significantly lower your risk of antibiotic-related diarrhea.

Probiotics are widely available in supermarkets and drugstores, but they're not all created equally. Products contain different strains of bacteria in different amounts, and they're largely unregulated.

Based on some of the research, Lactobacillus rhamnosus GG and Saccharomyces boulardii appear to be effective at preventing diarrhea while taking antibiotics. However, research continues into the best choices.

Some probiotic bacteria secrete compounds that inhibit the toxins produced by C. difficile, while others directly inhibit the organism. These could be in the product you buy, or it could contain something completely different.

As always, talk to your doctor before starting probiotics or any other supplements.

IBD and Antibiotics

If you have inflammatory bowel disease (IBD), especially with an ostomy or a j-pouch, it is important to talk to a gastroenterologist about antibiotics.

While various antibiotics have been explored as treatments for some types of IBD or its complications, antibiotics have been also been associated with IBD flare-ups and an increased risk of C difficile infection.

If you have IBD and are thinking of using a probiotic to repopulate your digestive system after a course of antibiotics, discuss it with your gastroenterologist first.

A Word From Verywell

A bacterial infection may need to be treated with antibiotics, and there may be no way of getting around that. The choice of antibiotics used won't be based on whether or not it has a low risk of C difficile colitis, but rather on what is the right choice for killing the bacteria that are causing your infection.

If you have concerns about having problems with diarrhea after taking antibiotics, talk to your physician. In some cases, there may be some leeway with which antibiotic to use, but it has to be effective against the bacteria that is causing the infection.