The Misuse of Drugs Act 2001 means that there are many legal requirements relating to the prescribing of opioid analgesics. Do you know what these are? The BNF provides guidance on prescribing for Controlled Drugs and drug dependence.

A patient with cancer related pain has been well controlled on oral morphine, taking morphine sulphate modified release tablets 40mg twice daily. They are dying, are unable to swallow their medications; therefore the decision is made to commence a syringe driver.

  • What dose of morphine syringe driver would you prescribe for them?
  • When would you stop the modified release morphine and start the morphine syringe driver?
  • What would you prescribe them for breakthrough pain?

Case study
Subcutaneous opioid is twice as potent as oral. The 24 hour subcutaneous dose should be half of the total 24 hour modified release dose. In this case it would be (40 x 2) = 80 / 2 = 40mg CSCI over 24 hour. Modified release opioids have duration of action of 12 hours. Syringe drivers will take 4 hours or more to reach steady state. The syringe driver should therefore be started 4 hours before the next dose of the morphine sulphate modified release tablets is due and then the tablets stopped. If the patient can swallow liquids, morphine sulphate immediate release oral solution can be prescribed on an as required (PRN) basis for breakthrough pain, however at end of life subcutaneous injections are more appropriate. The dose is usually a sixth of the regular total daily dose, given every hour if necessary at end of life. In this case, the dose would be 40 / 6= 7mg sc which could be rounded up to 10mg.

Copyright eBook 2019, University of Leeds, Leeds Institute of Medical Education.