What are the common side effects of bismuth compounds?

Bismuth compounds, commonly used to treat gastrointestinal ailments such as upset stomach and diarrhea, have a few notable side effects. The darkening of stool is a well-documented effect of bismuth subsalicylate, a common bismuth compound. This occurs because the bismuth interacts with sulfur compounds in the digestive tract, leading to the formation of bismuth sulfide, which has a dark coloration.

Additionally, constipation can occur as a side effect. Bismuth compounds can slow gastric motility and increase fecal firmness, contributing to a constipating effect, especially when taken in larger doses or over extended periods. These side effects are generally mild and resolve after discontinuation of the medication, making this option valid in the context of common adverse effects associated with bismuth.

The other choices presented do not align with the typical side effects of bismuth compounds, as diarrhea and headaches, coughing and fever, as well as hypertension and tachycardia are not commonly associated with their use.