What is a common drug used as an expectorant?

Guaifenesin is widely recognized as a common expectorant. It is utilized to help alleviate chest congestion by thinning mucus in the airways, which promotes easier clearance of mucus from the respiratory passages. This action can be particularly beneficial for patients experiencing coughs due to respiratory infections, colds, or allergies, as it aids in making the coughs more productive.

In contrast, the other medications listed serve different purposes. Ranitidine is an H2 receptor antagonist primarily used to decrease stomach acid production and treat conditions like GERD, while esomeprazole, a proton pump inhibitor, functions in the same area by suppressing gastric acid secretion. Codeine is an opioid that is commonly used as a cough suppressant due to its ability to depress the cough reflex, but it does not work as an expectorant and is typically used in cases where a reduced cough is desired, rather than encouraging mucus clearance.