Which of the following is a common side effect of fentanyl?

Fentanyl is a potent synthetic opioid used primarily for pain management, particularly in patients with severe pain or those who are tolerant to other opioids. One of the common side effects associated with the use of fentanyl and, generally, all opioids is nausea and vomiting. This reaction occurs due to fentanyl's action on the central nervous system, where it can stimulate the chemoreceptor trigger zone (CTZ) in the brain that activates nausea.

Opioids can influence gastrointestinal motility, leading to various effects, and nausea is one of the more frequent experiences reported by patients. The occurrence of this side effect is particularly prevalent at the initiation of therapy or when dosage increases are made.

On the other hand, while excessive sweating, dry mouth, and increased appetite may occur with various medications or conditions, they are not considered common side effects of fentanyl. Instead, those symptoms are more likely associated with different medications or physiological responses rather than this specific opioid.