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Drug reaction testing
Drug reaction testing uses a genetic test to
predict how a particular person will respond to various prescription
and non-prescription medications. It checks for genes that code
for specific liver enzymes which activate, deactivate, or are
influenced by various drugs.
There are currently four genetic markers commonly
tested for: 2D6, 2C9, 2C19, and 1A2.
This testing has been done for some time by
drug companies working on new drugs, but is relatively newly
available to the general public. Strattera is the first drug
to mention the test in the official documentation, although
it doesn't specifically recommend that patients get the test
before taking the medication.
There are four possible catagories for each
marker: Poor Metabolizer, Intermediate Metabolizer, Extensive
Metabolizer, or Ultra-Extensive Metabolizer. Different testing
companies may call these by different names. Extensive metabolizers
(that is, people who are Extensive Metabolizers of a given type)
are the most common, and are the type of people for which drugs
are designed. Poor Metabolizers make up about 7% of the population
for each enzyme, and around 50% of the population are poor metabolizers
of at least one type.
People who can't metabolize a drug will require
a much lower dose than is recommended by the manufacturer, and
those who metabolize it quickly may require a higher dose. Some
drugs, such as Codiene, will not be effective in people without
the requesite enzymes to activate them.
People who are Poor Metabolizers of a drug
may overdose while taking less than the recommended dose.