Fentanyl is an analgesic, an opioid agonist and a potent narcotic analgesic. The pharmacological effects are similar to morphine, and animal studies have shown that it is 80 times more effective than morphine as an analgesic. The analgesic effect of fentanyl is produced very quickly, but the duration is shorter, the general injection of 1 minute onset of action, 4 minutes to reach the peak of analgesia, the effect time is maintained for about 30 minutes. If it is injected intramuscularly, it takes about 7 minutes to take effect, and the long duration of action can last for 1-2 hours. Compared with morphine, the inhibitory effect on the respiratory system is weaker than that of morphine, and the adverse effects are also smaller than those of morphine. In clinical practice, fentanyl is mainly used for all kinds of pain, as well as pain after or during surgical and gynecological operations. Besides, it is also used to prevent and reduce the delirium state that occurs after surgery. In addition, it can also be used in combination with anesthetics as an anesthetic adjuvant, and can be paired with haloperidol to form a stabilizing analgesic, which can be used for analgesia in large-scale dressing changes as well as minor surgeries. In conclusion, fentanyl is a potent analgesic, and its pharmacological effects are similar to those of morphine. In addition, it should be noted that fentanyl is a psychotropic controlled substance, so the use of fentanyl must be in accordance with the relevant regulations, not unauthorized use of fentanyl.