Olanzapine Plus Metoclopramide for the Prevention of Opioid-Induced Nausea and Vomiting

Inclusion criteria 1. Patients with malignant tumors diagnosed by pathology or histology; 2. Patients diagnosed with locally advanced or advanced stages by imaging; 3. Age ≥ 18 years old; 4. The eastern cooperative oncology group (ECOG) performance status of 0-3; 5. The expected survival period shall be no less than 4 weeks; 6. Moderate or severe cancer pain with a Numerical Rating Scale (NRS) score of ≥ 4 points; 7. Be able to take oral medication; 8. Initial treatment with potent opioid painkillers (such as morphine, oxycodone, fentanyl, etc.); 9. No systemic chemotherapy or radiotherapy was received within one month prior to selection, and no drugs that may induce nausea and vomiting were used. 10. There were no gastrointestinal discomforts such as nausea or vomiting at the time of selection, and no intestinal obstruction. 11. Possess normal comprehension and communication skills, be capable of completing research evaluations and following research procedures. Exclusion criteria 1. Diabetic patients with a clear diagnosis and poorly controlled blood sugar levels; 2. There are symptoms of nausea or vomiting; 3. Symptomatic intracranial diseases, such as brain metastases or leptomeningeal metastasis; 4. Received chemotherapy drug treatment within one week before the trial medication or during the trial period; 5. Receive radiotherapy for the head, abdomen or pelvic cavity within one week before the trial or during the trial; 6. New drugs with emetic or antiemetic effects have been used within 48 hours before the start of the trial; 7. Patients with severe electrolyte imbalance, abnormal kidney or liver function; 8. Patients with gastrointestinal bleeding; 9. Pregnant or lactating women; 10. Patients diagnosed with breast cancer; 11. Those whose electrocardiogram examination indicates heart disease or prolonged QTc interval; 12. There is a history of allergy or contraindications to olanzapine or metoclopramide.