The (-) form of this SNP, representing a deletion of one nucleotide, causes a frameshift such that the resulting CYP2D6 protein is nonfunctional. The associated allele is also known as CYP2D6*6, and there are several subtypes but they are all nonfunctional.
If two copies of this (or similar) changes are inherited, CYP2D6 poor metabolism ('PM') is observed.
CYP2D6 poor metabolism may affect the efficacy or degree of side effects of drugs metabolized by CYP2D6, such as dextromorphan, sparteine, nortriptyline, venlafaxine and codeine.[PMID 20174590] Response to serotonin reuptake inhibitors in OCD is not influenced by common CYP2D6 polymorphisms.