Antibiotic-associated diarrhea

DEFINITION

Antibiotic-associated diarrhea describes frequent, watery bowel movements (diarrhea) that occur in response to medications used to treat bacterial infections (antibiotics).

Most often, antibiotic-associated diarrhea is mild and clears up shortly after you stop taking the antibiotic. But in some cases, antibiotic-associated diarrhea leads to colitis, an inflammation of your colon, or a more serious form of colitis called pseudomembranous colitis. Both can cause abdominal pain, fever and bloody diarrhea.

Mild antibiotic-associated diarrhea may not require treatment. More serious antibiotic-associated diarrhea may require stopping or switching antibiotic medications.

CAUSES

Antibiotic-associated diarrhea occurs when antibacterial medications (antibiotics) upset the balance of good and bad bacteria in your gastrointestinal tract.

The antibiotics most likely to cause diarrhea

Nearly all antibiotics can cause antibiotic-associated diarrhea, colitis or pseudomembranous colitis. The antibiotics most commonly linked to antibiotic-associated diarrhea include:

• Cephalosporins, such as cefixime (Suprax) and cefpodoxime
• Clindamycin (Cleocin)
• Penicillins, such as amoxicillin (Amoxil, Larotid, others) and ampicillin
• Fluoroquinolones, such as ciprofloxacin (Cipro) and levofloxacin (Levaquin)

How antibiotics cause diarrhea

Your digestive tract is a complex ecosystem that’s home to millions of microorganisms (intestinal flora), including hundreds of species of bacteria. Many of these bacteria are beneficial, performing essential functions.

But some of the bacteria that normally inhabit your intestinal tract are potentially dangerous. These harmful bacteria are usually kept in check by beneficial bacteria unless the delicate balance between the two is disturbed by illness, medications or other factors.

Antibiotics can be especially disruptive to intestinal flora because they destroy beneficial bacteria along with harmful ones. Sometimes, without enough “good” microorganisms, “bad” bacteria that are resistant to the antibiotic you received grow out of control, producing toxins that can damage the bowel wall and trigger inflammation.

Clostridium difficile causes most serious antibiotic-associated diarrhea

The bacterium responsible for almost all cases of pseudomembranous colitis and many instances of severe antibiotic-associated diarrhea is C. difficile. Most people acquire a C. difficile infection during a stay in a hospital or nursing home after they’ve received antibiotics.

SYMPTOMS

Antibiotic-associated diarrhea can cause signs and symptoms that range from mild to severe.

Common signs and symptoms

For most people, antibiotic-associated diarrhea causes mild signs and symptoms, such as:

• Loose stools
• More-frequent bowel movements

Antibiotic-associated diarrhea is likely to begin about a week after you start the antibiotic therapy. Sometimes, however, diarrhea and other symptoms may not appear for days or even weeks after you’ve finished antibiotic treatment.

More-serious signs and symptoms

Some people experience a more serious form of antibiotic-associated diarrhea. When the overgrowth of harmful bacteria is severe, you may have signs and symptoms of colitis or pseudomembranous colitis, such as:

• Frequent, watery diarrhea
• Abdominal pain and cramping
• Fever
• Mucus in your stool
• Bloody stools
• Nausea
• Loss of appetite

When to see a doctor

Call your doctor right away if you experience signs and symptoms of serious antibiotic-associated diarrhea. These signs and symptoms are common to a number of conditions, so your doctor may recommend tests to determine the cause.