Someone asked me about possible Fentanyl addiction when using it for pain relief, so I am sharing it here hoping it helps someone else.
The brain has two responses to opioids. When no pain is present, it can trigger the euphoria people seek as a high (behavioral-leads to addiction). When pain is present, the opioid effect is bonded to pain receptors and basically "used up" while blocking the pain. There is very little that goes to the pleasure center of the brain.
Because cancer patients are looking to control pain for a better quality of life, the risk of addiction for those in moderate to severe pain is only about 10%. https://ascopubs.org/doi/10.1200/EDBK_100020 The prescribing doctor should have protocols in place to help prevent that from happening. People at higher risk are those with past or current addictions. Chemical dependence is due to a body adaptation. This is where you would need to taper off the medicine to allow the body to compensate. With fentanyl, chemical dependency is expected after several weeks to a few months. Fentanyl makes the body produce fewer endogenous opioids (natural opioids) so if you are on it long-term and decide to stop, you would taper down slowly to allow the body to pick up its production. -W