CYP2D6*29 is assigned decreased function based on moderate evidence in homozygous subjects and in vitro studies. Three subjects with CYP2D6*29/*29 genotype demonstrated decreased metabolism compared to CYP2D6*1/*29 subjects with a debrisoquine substrate (11470994). Similarly, four subjects with CYP2D6*29/*29 genotype demonstrated decreased metabolism compared to wildtype with dextromethorphan and metoprolol substrates (11823760). Multiple in vitro studies found CYP2D6*29 had decreased enzyme activity compared to wildtype with various substrates (11470994, 24647041, 30366777). Although one study found subjects with CYP2D6*29/*29 genotype demonstrated similar metabolism compared to wildtype with debrisoquine and codeine substrates (11823760) the experts did not find this result convincing due to the small sample size. Therefore, consensus among experts with decreased function with an activity value of 0.5 based on moderate evidence.