Which of the following is a potential adverse reaction of fentanyl?

Respiratory depression is a well-documented adverse reaction associated with fentanyl use. Fentanyl is a powerful opioid analgesic that acts on the central nervous system to alleviate pain, but one of its significant effects is the depression of respiratory function. This occurs because opioids can bind to receptors in the brain that are responsible for controlling the body's automatic breathing response. In cases of overdose, or when fentanyl is administered improperly or too quickly, the result can be significantly decreased respiratory drive, potentially leading to hypoxia or even respiratory arrest.

While other options like increased heart rate, temperature fluctuations, and skin rash can occur with various medications or conditions, they are not directly tied to fentanyl's primary pharmacological action or its adverse effects. Understanding the critical risk of respiratory depression with opioid use is essential for safe administration and monitoring during procedures involving moderate sedation. This awareness is crucial for healthcare providers to respond effectively in situations where a patient's respiratory status may be compromised.