Many methods to detect CYP2D6 poor metabolizers have been validated. Some of them are based on phenotyping (metabolism of dextromethorphan or debrisoquine) and some others on genotyping. Up to now, CYP2D6 pharmacogenetics has been restricted to the field of research, in spite of poor metabolizer profile concerns 5 to 10 % of caucasian population. Nevertheless, the polymorphism of CYP2D6 is responsible for the metabolism of many drugs, particularly of two opioids involved in pain management: codeine and tramadol, their metabolites representing the most effective part of the drug effect. So prescribing codeine or tramadol in a patient poor metabolizer for the CYP2D6 is likely to be ineffective in pain management.