How common are poor or ultrarapid metabolizers of cytochrome P450 2D6?

Pharmacogenetic polymorphisms (variations) of the genes that code for various cytochrome P450 (CYP450) enzymes can lead to major changes in the metabolic activity of these enzymes. Due to these variations, for each CYP450 enzyme, a person can be a(n): – “Extensive (or normal) metabolizer” (EM) – “Poor metabolizer” (PM): The metabolic activity of the enzyme…