Pain injections usually take 5-10 minutes to take effect and can last up to 12 hours after injection. Pain relief injections are mainly used for early analgesia after surgery, patients who cannot tolerate oral medication or severe pain caused by advanced cancer, and have a fast onset of action, usually lasting about 6-8 hours, and some patients can reach 12 hours. Pain relief injections include the following three types of drugs: 1) non-steroidal antipyretic painkillers, such as ibuprofen, diclofenac sodium, celecoxib and parecoxib sodium for injection; 2) central painkillers, such as tramadol injection; 3) narcotic painkillers, such as pethidine hydrochloride injection, morphine sulfate injection, etc. The choice of pain medication should be decided according to the degree of the patient’s pain, and the patient’s condition. Pain injections should not be used arbitrarily to avoid the formation of certain drug resistance and organism dependence. After the patient’s pain symptoms are relieved, it is recommended to stop the medication or choose oral pain medication.