What medications cause diarrhea?

The NIH names the suspects directly: antibiotics, antacids containing magnesium, and medicines commonly used to treat cancer may cause acute diarrhea. Antibiotics are the famous one, and the mechanism is collateral damage: they kill gut bacteria along with the target, and the imbalance loosens everything, usually settling after the course ends. Magnesium antacids work as mild laxatives by design chemistry. Metformin, the first-line diabetes drug, causes loose stools in a large share of new users, typically easing over weeks, and the extended-release version is gentler. Cancer drugs hit fast-dividing gut lining cells. The sneaky one the NIH flags: some liquid medicines contain sugar alcohols like sorbitol, mannitol, and xylitol, which pull water into the gut, and switching to tablet form solves it. The rules of response: tell the prescriber rather than quitting, because the antibiotic case has a caveat, finishing the course usually matters, and severe or bloody diarrhea on antibiotics needs a call promptly since C. difficile is the dangerous version; ask about formulation changes, extended-release metformin, tablets instead of liquids, before accepting misery; and hydrate, because the medicine is less dangerous than the dehydration. Diarrhea lasting past the end of the drug course, or with blood, fever, or severe pain, is a get-seen pattern.