At the first visit, a detailed medical history is taken, including previous analgesics and concomitant treatment. After inclusion, patients enter a 4-week observation period during which they will receive bid of TARGIN 10/5mg and/or 20/10mg. The dose adjustments of TARGIN as well as of analgesic co-medication, rescue-medication and other treatments (e.g. laxatives) can be performed at any time-point during the observation period by the physician in dependence of medical demand. The asymmetric dose is allowed during the observation period by the physician's judgment. (e.g. 10/5 mg in the morning and 20/10 mg in the evening).