|
A person’s genetic makeup not only determines
his or her predisposition to developing certain conditions;
as researchers are discovering, it also can impact how
an individual’s body responds to a specific drug.
Whether a drug is metabolized slowly or quickly, or
if the medication has the desired effect or does not
work well, may be due to certain genetic variations.
Pharmacogenetics, the study of how genetics influence
a person’s response to a drug, began in the 1950s.
Then, the emphasis was on how certain ethnic groups
metabolized drugs; today, with advancements such as
gene and protein sequencing, the focus is on the individual.
With the new technology and a sample of cheek cells
or blood, a person’s genotype, a specific genetic
code, can be produced.
Cytochrome P450
A genotype provides all types of information, including
whether there are gene variations that affect the way
the body reacts to certain drugs. Of particular interest
is the Cytochrome P450, a group of enzymes that process
chemicals in the body. The genetic variations of P450
can affect how a drug is metabolized and how long it
remains in the body. This information is important,
because if the drug is metabolized too quickly, the
patient might not receive the medicine’s full
effect. Slowly metabolized drugs present a different
problem: otherwise perfectly acceptable doses of a medicine
could build up in a person’s body to the point
of toxicity.
P450 is involved in the body’s processing of
many of the most widely prescribed medications, including
antidepressants, blood thinners, and beta blockers.
By testing the blood for P450 variations, a doctor can
make any necessary adjustments in dosage or prescribe
a different medication altogether. For example, a person
who has the slow-metabolizing form of Cytochrome P450
2C9 enzyme, which metabolizes coumadin, may need a lower
dose than other people without the genetic variation.
Persons who have had adverse reactions or less than
satisfactory responses to medications processed by Cytochrome
P450 may be candidates for testing.
A More Individualized
Treatment Plan
Today’s advances in pharmacogenetics are but
the tip of the iceberg. The more that is known about
the interrelationship between human genes and medication,
the more relevant information physicians will have when
prescribing drugs for specific individuals. For example,
wholesale withdrawal from the market of drugs, such
as Vioxx, that are helpful to a large number of people,
but dangerous to others, could be avoided if genetic
variations leading to harm could have been identified
ahead of time.
|
Pharmacogenetics
Printer
Friendly Page