Early Use of Opioid in Radiation Mucositis

Inclusion Criteria: 1. Histological confirmed nasopharyngeal carcinoma; 2. Without historic chronic pain, no depend on analgesic drugs, no historic opioids intake; 3. Plan to receive radical radiation therapy, newly to radiation for head and neck; 4. Aged older or equal to 18 years old; 5. Could understand and cooperate to accomplish pain evaluation and observation scales; 6. Sufficient liver and kidney function: alanine aminotransferase (ALT) or aspartate aminotransferase (AST) less than 2.5\* upper limit of normal (ULN), serum creatinine less than 1.5\*ULN; 7. Without other serious critical organ dysfunction, such as heart or lung dysfunction; 8. Performance status (PS) score less than 2; 9. Voluntary to participate and sign informed consent document; 10. Obey the rules of trail; could be followed-up on time. Exclusion Criteria: 1. Excluded by inclusion criteria; 2. Known or suspected allergy to nonsteroidal anti-inflammatory drug (NSAID) or opioid medicine; 3. Unable to complete the follow-up; 4. Severe uncontrollable infections of medical disorders; 5. Major organ including heart, lung, kidney, or liver dysfunction; 6. With pathophysiological factors affecting drug absorption, distribution, metabolism or excretion.