CYP2D6*44 is assigned no function based on limited evidence in a heterozygous subject. CYP2D6*44 was identified in a subject with CYP2D6 *2/*44 genotype demonstrating decreased dextromethorphan metabolism compared to CYP2D6 *1/*2 subjects (15618746). CYP2D6*44 is defined by a splicing defect yielding a nonfunctional protein. Therefore, consensus among experts was no function with an activity value of 0 based on limited evidence.