Direct DNA testing will not detect all known mutations that result in decreased or inactive CYP2D6. Absence of a detectable gene mutation or polymorphism does not rule out the possibility that a patient has an intermediate or poor metabolizer phenotype.
This test does not detect polymorphisms other than those listed. Gene duplications may occur by other mechanisms and may not be detected. Other polymorphisms in the primer binding regions can affect the testing, and ultimately, the genotyping assessments made. Testing may reflex to DNA sequencing to resolve difficult genotypes or to confirm interpretations.
Patients with an extensive or intermediate metabolizer genotype may have CYP2D6 enzyme activity inhibited by a variety of medications or their metabolites, including many tricyclic antidepressants (TCA’s), selective serotonin reuptake inhibitors (SSRI’s), many histamine H-2 receptor antagonists, amiodarone, celecoxib, cimetidine, cocaine, methadone, quinidine, and ritonavir, as well as several other drugs. Treatment with drugs that are inhibitors of CYP2D6, or produce inhibitors through metabolism, may generate a poor metabolizer phenotype in an individual who has an extensive or intermediate metabolizer genotype.
CYP2D6 alleles with “reduced function” may metabolize different drugs at different rates, ranging from near normal to poor but the literature on this is incomplete at this time.
The drug application that we currently that we currently support for testing and interpretation is for the treatment of depression and other psychiatric disorders.
This test is not for use in assessing for autoimmune hepatitis. Autoantibodies for CYP2D6 enzyme are found in many cases of autoimmune hepatitis.