Mrs Ray is an 82 year old lady who has a terminal diagnosis of metastatic renal cancer and is being cared for at home by the district nurses. Pain is her predominant symptom which was controlled by taking Morphine Sulphate modified-release tablets with her dose stable at 40mg twice daily. No breakthrough doses of Morphine were required. She has deteriorated further however and a syringe driver has been commenced for her consisting of subcutaneous Morphine only.
Unfortunately, this produced intolerant side effects and a decision is made to convert her subcutaneous dose of Morphine into subcutaneous Oxycodone via the syringe driver. What is the approximate dose of subcutaneous Oxycodone over 24 hours that should be prescribed?