Palliative symptom control in the community — KFP-style written assessment

KFP 1 (10 marks)

A 62-year-old woman with metastatic breast cancer has moderate-to-severe pain. Her eGFR is 22 mL/min. She is currently on paracetamol alone. ^[1]

1. Which opioid class should you avoid and why? (4) ^[1]
2. What should you prescribe instead? (3) ^[1]
3. What breakthrough dose rule applies? (3)

Model answers

1. Avoid morphine and codeine. Morphine produces active metabolites M6G (analgesic) and M3G (neuroexcitatory) that are cleared renally; at eGFR 22 they accumulate causing sedation, myoclonus and respiratory depression. Codeine is also renally cleared with active metabolites. ^[1]
2. Prescribe a fentanyl patch for background analgesia plus low-dose subcutaneous fentanyl PRN for breakthrough. Buprenorphine patch is an alternative. Both undergo hepatic metabolism without active renally-cleared metabolites. ^[1]
3. Breakthrough dose equals one-sixth of the total 24-hour opioid dose, given PRN by the same route. Two or more PRN doses in 24 hours means the background dose should be increased. ^[1]