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There has been much research on CYP450 enzymes and many papers reporting polymorphisms with clinical significance. 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, intermediate, extensive (normal), or ultra-rapid metabolizers.