morphine/codeine ratio, a key in investigating a case of doping

Introduction: consumption of codeine can lead to positive urine test for morphine in athletes. morphine is classified as a prohibited doping drug while codeine is not. morphine/codeine ratio is used in forensic medicine to distinguish the consumption of codeine from abuse of morphine and other narcotics. case presentation: we present an athlete with positive urine test for morphine with a history of consumption of codeine. the disciplinary committee came to conclusion that the athlete had not consumed morphine and did not violate doping code based on morphine/codeine ratio. conclusions: analysis of codeine to morphine metabolism rate is needed when we are using morphine/codeine ratio to rule out abuse of narcotics. wada should consider analysis for the cyp2d6 alleles (main metabolizer of codeine) in case of including morphine/codeine ratio in future prohibited list. the possibility of ultra-rapid cyp2d6 cannot be ruled out in certain results of morphine/codeine near the cut point.