Much research has been done on CYP450 enzymes and many polymorphisms with clinical significance have been reported. We can't discuss all CYP450s but lets consider CYP2D6 as an example:
- It is estimated that about 25% of common drugs are metabolized by CYP2D6.
- CYP2D6 accounts for only about 1% of all CYP450 enzymes, but it is important in the metabolism of about 100 drugs.
- There are more than 80 genetic variants that have been described in the CYP2D6 gene. The normal, wild-type allele displays normal metabolic activity whereas some of the variant forms have enhanced or diminished activity.
- The variants can be grouped generally according to the resulting alterations in protein function.
- The groupings correlate with four major enzyme metabolic capacities (phenotypes):
- poor metabolizers
- intermediate metabolizers
- extensive (normal) metabolizers
- ultra-rapid metabolizers