• The primary outcome measure is the IVRS 11-point Numeric Rating Scale pain score (average pain) during the last three days of week 5.
  

• Cumulative average pain response curves
  
• Mean daily IVRS NRS pain score (average and also worst pain).
  
• Brief Pain Inventory - Short Form
  
• Sleep Disruption NRS
  
• Patient Assessment of Constipation Quality of Life (PAC-QoL)
  
• Patient Global Impression of Change - PGIC
  
• Montgomery Asberg Depression Rating Scale (MADRS)
  
• Addiction Research Center Inventory (ARCI)
  

Inclusion Criteria:

• The patient has advanced active cancer for which there is no known curative therapy.
• The patient is able (in the investigators opinion) and willing to comply with all study requirements.
• The patient has a clinical diagnosis of cancer related pain, which is not wholly alleviated with their current opioid treatment.
• The patient is receiving a sustained release (SR) fixed dose of opioid therapy (excluding Methadone). N.B. The opiate therapy must be Step III according to the WHO analgesic ladder.
• The patient is willing to continue to take their regular daily baseline opioid regimen (SR) at the same dose, throughout the duration of study.

Exclusion Criteria:

• The patient should be excluded from entering study if they have received or are due to receive during the study period; chemotherapy, hormone therapy or radiotherapy, which, in the opinion of the investigator will affect their pain.
• The patient is currently using two or more types of break-through opioid analgesia (IR).
• Any history or immediate family history of schizophrenia, other psychotic illness, severe personality disorder or other significant psychiatric disorder other than depression associated with their underlying condition.
• Any known or suspected history of a diagnosed dependence disorder, current heavy alcohol consumption, current use of an illicit drug or current non prescribed use of any prescription drug.
• The patient has poorly controlled epilepsy or recurrent seizures (i.e. at least one year since last seizure).
• The patient has experienced myocardial infarction or clinically relevant cardiac dysfunction within the last 12 months or has a cardiac disorder that, in the opinion of the investigator would put the patient at risk of a clinically relevant arrhythmia or myocardial infarction.