A 72-year-old man with metastatic colorectal cancer and chronic kidney disease is admitted with sepsis. After three days of treatment, he deteriorates. Following discussions, the decision is made to discontinue antibiotics and fluids, focusing on end-of-life care.

His current analgesia is paracetamol 1g QDS, morphine sulfate modified release (long-acting) 90mg BD, and morphine sulfate immediate release oral liquid (short acting) 30mg PRN, 4-hourly. He has used 4 doses of the PRN oral morphine in 24hrs.


His eGFR is 22 mL/min/1.73m². The patient asks if his oral medications can be reduced or converted to a syringe driver due to difficulty swallowing.

Which of the following prescriptions would be most suitable for this patient?

Options:
explanation: Morphine sulfate accumulates in renal failure with eGFR <45mL/min/1.73m2 and so the choice of opioid should be changed to one with less renal excretion. In those with eGFR 10-30mL/min/1.73m2, the most common choice is oxycodone. With eGFR <10mL/min/1.73m2, the most common choice is alfentanil.
 

 This would be the correct dosing of alfentanil, although paracetamol is not available as a subcutaneous injection and so must be given orally or IV
name: 10mg alfentanil/24hrs and 4g/24hrs paracetamol subcutaneously via a syringe driver with 7.5-12.5mg subcutaneous oxycodone as required 4-hourly for breakthrough pain
label: e
answer: no
explanation: This patient is on 90mg twice daily of morphine sulfate modified release and has used 4 doses of 30mg morphine immediate release, equating to a total of 300mg oral morphine sulfate in24hrs.
 

 Morphine sulfate accumulates in renal failure with eGFR <45mL/min/1.73m2 and so the choice of opioid should be changed to one with less renal excretion.
 

 In patient such as this one, with eGFR 10-30mL/min/1.73m2, the most common choice is oxycodone.
 

 To convert between opioids, always convert to the 24hr dose of oral morphine from the current opioid regime and then convert to the new drug of choice.
 

 If you are unsure, always look up conversions online or in your local trust guidance. The following table shows dose equivalents of 10mg oral morphine
 

| Analgesic/Route | Dose | Conversion Factor |
| -------------- | ------- | ----------------- |
| Codeine/tramadol/dihydrocodeine oral | 100mg  | x10  |
| Diamorphine IM/IV/Subcut  | 3mg  | ÷3.3 |
| Morphine IM/IV/Subcut | 5mg  | ÷2 |
| Oxycodone oral\*  | 6.6mg\*  | ÷1.5\* |
| Oxycodone Subcut\*  | 5mg\* | ÷2\* |
| Alfentanil Subcut | 0.3mg  | ÷30  |
 

 \*NB - oral oxycodone potency is between 1.3-2x that of oral morphine. Different trusts will adopt different guidance on which you should use. If in doubt, always opt for the lower dose and titrate up.
 

 This patient is on 300mg/24hrs oral morphine equating to 150mg subcutaneous oxycodone/24hrs. Breakthrough analgesia dose is calculated 1/10th-1/6th the 24hr dose. This equates to 15mg-25mg subcutaneous oxycodone as required.
 

 Paracetamol is not available as a subcutaneous injection and so must be given orally or IV. Often when patients approach the end of their life intravenous medications are stopped or converted to other routes to avoid repetitive cannulations
name: 150mg oxycodone/24hrs subcutaneously via a syringe driver with 15-25mg subcutaneous oxycodone as required 4-hourly for breakthrough pain
label: a
answer: yes
explanation: Morphine sulfate accumulates (increased side effects and risk of overdose due to accumulation of active/toxic metabolites) in renal failure with eGFR <45mL/min/1.73m2 and so the choice of opioid should be changed to one with less renal excretion. In those with eGFR 10-30mL/min/1.73m2, the most common choice is oxycodone. Also note the 24hr dose of oral morphine sulfate is 300mg in this scenario. Always make sure to calculate total 24hr doses in twice daily dosed long-acting opioids
name: 210mg morphine sulfate/24hrs subcutaneously via a syringe driver with 20-35mg subcutaneous morphine sulfate as required 4-hourly for breakthrough pain
label: c
answer: no
explanation:  This patient is on 300mg/24hrs oral morphine equating to 150mg subcutaneous oxycodone/24hrs. Subcutaneous oxycodone is twice as potent as as oral morphine
name: 75mg oxycodone/24hrs subcutaneously via a syringe driver with 7.5-15mg subcutaneous oxycodone as required, 4-hourly for breakthrough pain
label: b
answer: no
explanation: This patient is on 300mg/24hrs oral morphine equating to 150mg subcutaneous oxycodone/24hrs, therefore this answer is incorrect.
name: 35mg oxycodone/24hrs and 4g/24hrs paracetamol subcutaneously via a syringe driver with 4-6mg subcutaneous oxycodone as required 4-hourly for breakthrough pain
label: d
answer: no

Correct answer: a

75mg oxycodone/24hrs subcutaneously via a syringe driver with 7.5-12.5mg subcutaneous oxycodone as required 4-hourly for breakthrough pain

Learning point: In patients with renal impairment (eGFR <45 mL/min/1.73 m²), morphine sulfate should be converted to oxycodone using a rough equivalence of 1 mg morphine to 0.6 mg oxycodone, with dose reductions of 25-50% considered to prevent accumulation and side effects.