The use of fentanyl patches has become accepted as standard in Germany for the treatment of chronic and cancer pain. Recently generic fentanyl patches were launched but in contrast to the original patches the new patches are without labels concerning the concentration. There is not only a difference of ca 30% in the fentanyl concentration among the different generic patches, there is also a variation in the size. Especially in hospitals, nursing homes or in emergency cases the dose of the patches cannot be distinguished by doctors, nurses or other healthcare providers which can lead to overdoses or to withdrawal reactions with one of the strongest opioids available. In cases where problems occur the prescribing doctor will be held responsible.