Diamorphine Solubility Advantage — SCE Palliative Medicine MCQ

Instant feedback + full explanation. One question, done properly.

ModerateSyringe Driver & Drug CompatibilityDiamorphine Solubility AdvantageSCE Palliative Medicine

A patient on a continuous subcutaneous infusion (CSCI) via syringe driver containing diamorphine 80 mg/24 h is developing tolerance and needs a dose increase. The pharmacist is concerned about the maximum practical concentration of diamorphine in the syringe driver. What is diamorphine’s key advantage over morphine for CSCI use?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — Greater aqueous solubility permits concentrated CSCI dosing

Explanation lettering: D = shown as C · E = shown as D · C = shown as E

The correct answer is B. In CSCI practice, diamorphine’s substantially greater water solubility compared to morphine allows clinicians to deliver higher doses in smaller syringe volumes — a vital factor when escalating dose in opioid‑tolerant patients. UK regional guidelines emphasise that morphine’s lower solubility may lead to impractically large injection volumes, whereas diamorphine remains physically manageable even when concentration needs to increase ([england.nhs.uk](https://www.england.nhs.uk/north/wp-content/uploads/sites/5/2018/06/Palliative_Care_Prescribing_Guidelines_-_May_2014_Blackpool.pdf?utm_source=openai)). Why other options are incorrect: A is incorrect — diamorphine does not have more formulations. C is wrong — both are mu‑opioid agonists with the same mechanism. D is incorrect — potency is similar when equianalgesic. E is false — at equivalent analgesic doses side‑effect profiles are essentially the same.

Reference: Lancashire & South Cumbria Palliative Care Prescribing Guidelines (2014); Right Decisions Scotland (morphine solubility and diamorphine solubility guidance), https://www.england.nhs.uk/north/wp-content/uploads/sites/5/2018/06/Palliative_Care_Prescribing_Guidelines_-_May_2014_Blackpool.pdf