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There are currently
three categories of
Pharmacogenomic
information in drug
labels according to the
FDA:
i
)
Tests required for
prescribing
ii
)
Tests
recommended
when prescribing
iii
)
Pharmacogenomic
information for
information only
this can only happen if physicians and
other health
-
care professionals, as well as
patients, are being educated and become
knowledgeable about pharmacogenomics
.
Te need for public education in this feld
has never been more noticeable
:
recent
reports about drug safety issues and the
withdrawal of well
-
known drugs from
the marketplace illustrate how important
public awareness and knowledge in this
feld has become
.
Tese recent reports
and the increased public awareness of
drug safety, provide an unprecedented
opportunity to alter dramatically the way
modern medicine is performed
.
Tis
impetus could provide the much needed
and long anticipated start to integrate
personalized
(
or targeted
)
medicine into
everyday practice
.
Regulatory action can be
taken at the level of providing information
to physicians, patients, and other health
-
care providers via drug labels
(
package
inserts
).
Pharmacogenomics can play an important
role in identifying responders and non
-
responders to medications, avoiding
adverse events, and optimizing drug
dose
.
Although scientists frst noticed in
the 1930s that natural genetic variations
caused patients to respond diferently to
some medications, information about
pharmacogenomics didn’t appear on a drug
label until 2004
.
Te frst drug approved
on the basis of ‘pharmacogenomic’ testing,
Trastuzumab
(
Herceptin®
)
, indicated for
the treatment of breast cancer, is prescribed
only if HER2
/
neu gene is over expressed
in the tumor
.  
In August 2007, the FDA
added information to the widely prescribed
blood thinner’s
(
warfarin
)
label saying that
patients with variations in two diferent
genes might need a lower dose
.
Other
examples include
:
6
-
mercaptopurine
(
6
-
MP
)
, which is used to treat acute
lymphoblastic leukemia in children
.
Based
on a discussion of the FDA›s pediatric
subcommittee, the 6
-
MP label has been
updated from its original version and now
states that ‹substantial dosage reductions
may be required to avoid the development
of life
-
threatening bone marrow
suppression in these patients›
.
Another
recent example is the label for Erlotinib
(
Tarceva®
)
, indicated for the treatment of
non
-
small
-
cell lung cancer
.
Te label states
an apparent larger survival efect in patients
with epidermal growth factor receptors
(
EGFR
)
whose density is determined by the
presence of specifc genes
.
Te list of FDA
-
approved drugs with pharmacogenomic
information in their labels is given at
USFDA website www
.
fda
.
gov
.
Pharmacogenomics has the overarching
goal of developing safer, more efective
drugs, and ensuring that patients receive
the correct dose of the correct drug at
the correct time
.
Some pharmacogenetic
tests, primarily those related to drug
metabolism have well
-
accepted
mechanistic and clinical signifcance and
are currently being integrated into drug
development decision making and clinical
practice
.
Tis fact is well illustrated by
succinylcholine whose muscular paralysis
action increases from few minutes to
few hours due to lack of metabolizing
enzyme
(
pseudocholinesterase
)
in the
blood
.
Tis may result in respiratory
paralysis and death
.
Antitubercular drug,
isoniazid, leads to neuropathy in patients
due to slow metabolism by acetylation
.
Antimalarial
(
primaquine and quinine
)
and
antimicrobial drugs like sulphonamides
and nitrofurantoin cause hemolytic anemia
in patients with Glucose
-
6
-
phosphate
reductase enzyme defciency
.
All these
toxic efects have been clearly assigned
to genetic defects in certain individuals
.
Te promise of pharmacogenomic lies
in its potential to help identify sources
of inter
-
individual variability in drug
response
(
both efectiveness and toxicity
)
;
this information will make it possible to
individualize therapy with the intent of
maximizing efectiveness and minimizing
risk
.
However, the feld is currently in early
developmental stages, and such promise
has not yet been realized
.
The reports clearly state that
pharmacogenetic research
deserves support from all
concerned, but cautions not to
create unrealistic expectations.
This is one of the virtues that
good educators must address:
Pharmacogenomics will not
replace, but enhance, existing
good medical practice. A
deliberate approach starts
with educating young medical
professionals by illustrating the
benefts of pharmacogenomics
and setting realistic expectations.
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