Mr Casper is a 70 year old male with advanced lymphoma and you are due to see him on a GP home visit. The district nurse asks you to review his analgesia as he is using Oramorph 5mg 8 times daily. In addition to this he takes Morphine Sulphate 40mg modified-release tablets twice daily.
What dose of Morphine Sulphate modified-release tablets should you consider increasing him to?