Part II.
Pharmacogenes code for metabolic enzymes
Most medications rely on metabolic enzymes in the liver to be detoxified and eliminated.
Some medications are prodrugs and rely on metabolic enzymes to be activated.
In phase 1 of metabolism:
- Drugs are converted by enzymes to more water-soluble compounds to facilitate elimination.
- CYP2C9, CYP2C19 and CYP2D6 are examples of phase 1 metabolic enzymes and are responsible for the metabolism of approximately 80% of frequently prescribed drugs.
In phase 2 of metabolism:
- Medications are acted upon by metabolic enzymes that work to convert the drug to an inactive form.
- UGT, GST, NAT and TPMT are examples of common phase 2 metabolic enzymes.
Genetic variations of Phase 1 and Phase 2 genes are very common and can affect the efficacy or risk of adverse effects of many medications including antidepressants, pain medications, cardiac drugs, some anticancer drugs etc.
Preemptive pharmacogenetic (PGx) testing, via a simple cheek swab, can determine if genetic variations of metabolic enzymes are present. These results can be used to guide the selection of medications that are more likely to offer benefit and less likely to cause harm.
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