Drug Metabolism - Liver Enzyme CYP2D6 ('two D six')

CYP2D6 is needed to process half of common medications! Avoid serious side effects.

When considering drug safety and effectiveness, the level of activity of this enzyme is likely to be most important. A long list of medications is processed by CYP2D6. These include antidepressants, antipsychotics, antiarrhythmics, antiemetics, beta blockers and opioids, not to mention activation of tamoxifen.

CYP2D6 has normally active forms, forms that are partially active, and forms completely without activity. There are also duplicated active forms that multiply the level of activity.

Your level of activity is inherited from your parents:

• UM: Persons who have inherited one or two copies of duplicated active forms have ultra-rapid metabolism (UM). They require higher drug doses to benefit from certain medicines. They also rapidly convert certain drugs like codeine to potent derivatives like morphine, resulting in overdose.
• EM: Persons who have one or two copies of normally active forms have normal extensive metabolism (EM).
• IM: Persons who have one or two copies of reduced function forms, who lack more active forms, have reduced intermediate metabolism (IM). They may require lower doses of some medications, and may be at greater risk of side effects compared to those who have normal EM.
• PM: Persons who have two copies of inactive forms have poor CYP2D6 metabolism (PM). They frequently require lower drug doses to avoid side effects. They do not benefit from medicines that require processing to the active form of the medication.

You should know your level of CYP2D6 and share this information with your physician when he prescribes medications! Unlike many lab tests, this information only has to be tested once! It does not change over time.

Our test investigates an extensive battery of polymorphisms ('forms') to identify those that you have inherited -- and your level of activity. This information is expected to be very useful in selecting medicines likely to be safe and effective for you, and in adjusting drug dosage. Examples of how clinical outcomes vary according to the level of CYP2D6 activity are given here. No claim is made that all aspects of CYP2D6 metabolism are investigated. Discuss this information with your physician.