 Current treatments for breakthrough cancer pain BTCPwork too slowly to meet the fast onset of most BTCP episodes, they continue to act longer than the episode of pain lasts and so can have unwanted side effects due to this over treatment of the pain episode. In addition many cancer patients have oral problems which make taking pain relief medication by mouth uncomfortable for the patient. Nasalfent is administered via the nose as a simple spray and can be taken by patients or given by their carers. The nasal route is a common way to administer medication for example in the treatment of migraine or allergy. At any time during the study the patient may take their regular treatment for BTCP should they so wish. 