1.World Health Organization (WHO) data show that cancer pain is a global health problem, with about 5.5 billion people worldwide (83% of the world’s population) living in areas where restricted drugs are difficult or impossible to obtain, and about 5 million advanced cancer patients suffer from cancer pain every year. 2. If acute pain is not completely controlled, it may develop into chronic pain; if chronic pain is not treated early, it will develop into nerve sensitization and form pain memory, leading to intractable pain. Therefore, pain should be treated early and controlled as soon as possible. 3. Oral administration is simple, economical and easy to accept, with convenient dose adjustment and patient autonomy, stable blood concentration, not easily addicted and resistant to drugs, and the effect is comparable to intravenous injection. Therefore, oral administration should be preferred for the treatment of cancer pain. 4.Treatment of cancer pain must be administered on time. Timely drug administration can keep the blood concentration of patients stable, better control pain and ensure continuous pain relief. However, if the patient has a brief but severe outbreak of pain, a certain amount of morphine immediate release tablets can be given according to the condition. If there are more than 3 outbreaks of pain in 24h, the drug dose should be increased. 5. Individuals vary greatly in their sensitivity to narcotic drugs, so there is no standard amount of opioids. Individualized dosing is important. 2016 NCCN General Principles of Opioid Prescribing for Adult Cancer Pain emphasizes that the appropriate dose of opioids is the dose that provides pain relief and maximum improvement in patient function and does not cause unmanageable side effects. Moreover, the dose of the drug is not a once-and-for-all, and the dose of the drug can be increased when the original dose is not sufficient for analgesia. 6.Use NASIDs with caution. potential adverse effects of chemotherapy (especially anti-angiogenic inhibitors), such as blood (thrombocytopenia or coagulation), kidney, liver and cardiovascular system toxicity, can increase with the concomitant use of NASIDs. 7, If NASIDs are to be used for a long time or the daily dose has reached the restrictive dosage, should consider replacing it with an opioid; if it is a combination drug, only increase the dose of opioid analgesic medication. 8. For adult patients with normal hepatic function, the maximum daily dose of acetaminophen is 4 g. For long-term acetaminophen users, the upper daily dose limit is 3 g or less. Considering the presence of hepatotoxicity, acetaminophen should be used with caution or without the use of opioid-acetaminophen combinations. The “three-step pain rule” may no longer be necessary: there is increasing clinical evidence that for patients with Pain ≥ 4 (moderate to severe pain), low-dose strong opioids such as morphine or oxycodone can be chosen directly, which have better efficacy and similar adverse effects than weak opioids. 10. The analgesic strength of tramadol is 1/10 of morphine, and the maximum daily dose is 400 mg. The use of tramadol should be reduced in elderly people over 75 years old and patients with hepatic or renal insufficiency to reduce the risk of epilepsy. antidepressants, selective 5-hydroxytryptamine reuptake inhibitors, monoamine oxidase inhibitors) to prevent the development of 5-hydroxytryptamine syndrome. 11. Fentanyl transdermal patches should be used in opioid-tolerant patients and are not recommended for unstable pain patients who require frequent dose adjustments. Short-acting opioid titration should be performed until pain is well controlled before use.NCCN Adult Cancer Pain Guidelines 2016 Edition New: Avoid exposure of the site and periphery of fentanyl patch use to heat sources. Increased temperature accelerates fentanyl release and can lead to overdose and death. Fentanyl patches should not be cut or punctured. 12. Opioid switching is done to better balance analgesia and side effects. If side effects are significant, switch to an equivalent dose of another opioid. When switching between oral and parenteral routes of administration, the relative efficacy must be considered to avoid overdose or underdose. 13.Opioid resistance refers to the continuous increase in the dose of drugs used to maintain the analgesic effect. Most patients need more analgesic drugs because of the progress of the disease and increased pain, while psychiatric dependence (commonly known as “addiction”) refers to the search for drugs by any means, not for analgesia but for spiritual desire, and the two should not be confused. Cancer pain is a natural barrier to toxic anesthetic drugs, while most cancer pain treatment choose slow-release opioids, patients generally do not become addicted. 14, Strong opioid drugs can effectively control pain and reduce stress. However, it has been documented that some opioid drugs themselves can affect immune system function. Among them, morphine and fentanyl have a high degree of immunosuppression, and oxycodone has no immunosuppressive effect. 15.Even after the standardized three-step analgesic program there are still 10%-20% of intractable cancer pain cannot be relieved. At this time, minimally invasive intervention, radiation therapy, physical therapy and psychotherapy can be used to relieve pain.