Diarrhea can have many causes, including medications. Diarrhea is a common side effect of medications. For example:

• Laxatives can produce diarrhea by drawing water into the gut, increasing the muscular contraction of the intestine, lubricating the lining of the gut, or a combination of these effects.
• Antibiotics can produce diarrhea by destroying the normal bacteria of the gut. These normal, good gut bacteria are called probiotics. Once these "friendly" bacteria are destroyed, a bad organism called Clostridium difficile may then enter the digestive tract. It can cause a severe, watery form of diarrhea called pseudomembranous colitis.
• Other drugs may be directly toxic to the digestive tract. Chemotherapy medicines are a frequent example.

To prevent diarrhea related to antibiotic use, talk to your doctor about taking probiotic supplements. Continue taking these supplements for a few days after the course of antibiotics is complete.