MRCP2-3744

A 29-year-old woman with metastatic cervical cancer presents to the Medical Admissions Unit with uncontrolled pain and vomiting. She has been experiencing worsening back and pelvic pain for the last two weeks, but was reluctant to seek medical attention as she wanted to keep going for her three young children. Despite palliative treatment, her pain has become unbearable and she is now clinically dehydrated and in distress. Her lab results show elevated levels of serum urea, creatinine, and corrected calcium, as well as low albumin. What is the most appropriate analgesic for this patient?