Comparison of Oral Morphine Versus Nasal Ketamine Spray With Chitosan in Cancer Pain Outpatients

Inclusion Criteria: * Cancer pain in outpatients with: * Opioid based therapy due to pain * Breakthrough pain or * Extreme pain on movement * Age \>= 18 years Exclusion Criteria: * Patients unable to give written informed consent * Patients unable to understand how to handle and document the use of the study medication * Known drug allergies or intolerance to ketamine * Known drug allergies or intolerance to morphine * Known allergy to crustacea or chitosan * Patients using snuff at a regular basis * Recreational drug addiction or abuse * Serious intranasal or epipharyngeal Problems (Septum wall defects, cancer) * Mental/psychiatric disorder * Patients with renal failure (clearance \< 30 ml/min) * Pregnancy and breast feeding mothers * Patients not understanding German * Patient having arterial hypertonia with measured values \> 180/95