 This is a double -blind randomized crossover study to provide evidence for the expert advice based recommendation of the Expert Working Group of the European Association for Palliative Care EAPC that patients during treatment with IR morphine are given a double dose at bed-time that replaces the next 4-hourly dose during night. In addition to the primary, blinded clinical part of the study, an experimental part is also included. This part consists of two open study days were morphine IR is given in the same fashion as the clinical study. The aim is to study whether pharmacokinetic data supports the clinical data. 