This study is designed to assess the efficacy and safety of oxycodone in managing moderate to severe pain in patients with Alzheimer's disease. The trial will be conducted at Xuanwu Hospital, Capital Medical University, and will enroll 10 eligible participants. Participants will receive oxycodone/acetaminophen (5 mg/325 mg) once daily for 12 weeks. The treatment will follow international guidelines, with dosages adjusted based on the patient's baseline pain levels and individual needs. Dosages will be adjusted based on baseline pain levels and patient needs, following international guidelines. Efficacy and adverse events will be assessed at baseline, week 6, week 12, and at a 12-week post-treatment follow-up. The primary outcome is change in VAS pain scores; secondary outcomes include PAINAD, SF-36, functional ability, and safety profiles.