Opioids

A 58-year-old man with metastatic pancreatic cancer presents to the palliative care clinic with severe, uncontrolled pain (8/10 on visual analogue scale) despite being on paracetamol 1 g QID and ibuprofen 400 mg TDS for the past 3 weeks. On examination, he appears cachectic but alert and oriented. His respiratory rate is 16/min, oxygen saturation 98% on room air, and blood pressure 128/82 mmHg. The palliative care physician decides to initiate opioid therapy. Which of the following opioids is the most appropriate first-line choice for this patient?

Which opioid receptor subtype is primarily responsible for analgesia and respiratory depression?

A 58-year-old man with advanced pancreatic cancer on morphine 60 mg/day for cancer pain presents to the emergency department with severe respiratory depression (RR 8/min, SpO₂ 82% on room air) and pinpoint pupils. His wife reports he accidentally took a double dose 2 hours ago. What is the most appropriate immediate next step in management?

Which of the following opioids undergoes glucuronidation to form active metabolites that accumulate in renal failure?

A 72-year-old woman with chronic obstructive pulmonary disease (COPD, FEV₁ 35% predicted) and severe osteoarthritis of the knees is admitted to hospital with acute exacerbation of COPD. Her baseline respiratory rate is 18/min, PaO₂ 65 mmHg, and PaCO₂ 48 mmHg on supplemental oxygen. She has been on morphine 10 mg every 6 hours for pain control at home. The admitting physician prescribes morphine 15 mg IV stat for acute pain, followed by 10 mg IV every 4 hours. Within 2 hours of the first dose, the patient's respiratory rate drops to 10/min, PaO₂ falls to 52 mmHg, and she becomes drowsy. What is the most appropriate immediate management?