posted
Psychiatric News January 18, 2008 Volume 43, Number 2, page 7
More Prescribing Decisions to Be Guided by Genetic Tests
Jun Yan
Genetic discoveries, which are continuing to reveal why different people react to the same drug differently, are beginning to influence personalized drug therapy.
Genetics is asserting its importance in drug therapy and transforming how we understand and manage risks and effectiveness of treatment.
The Food and Drug Administration's (FDA's) recent requirement to add a genetic-testing recommendation to the label of carbamazepine and warfarin is just one indication of the changes leading to a future of more individualized patient care.
In December 2007, the prescribing information for the anticonvulsant carbamazepine--approved for neuropathic pain and seizure disorders such as epilepsy and with a long-acting version approved for episodes of mania and bipolar disorder I -- was revised to include the recommendation for a genetic test for a particular human leukocyte antigen (HLA) gene variation, known as HLA-B*1502 allele, in patients of Asian ancestry.
The allele is associated with greatly increased risk of the potentially fatal skin reactions of Stevens Johnson syndrome and toxic epidermis necrolysis.
One study conducted in Taiwan cited by the FDA in its announcements found that this allele was present in 59 of 60 patients with the severe skin reactions associated with carbamazepine and only 4 percent of those who tolerated the drug.
HLA-B*1502 is carried "almost exclusively in patients with ancestry across broad areas of Asia, including South-Asian Indians," according to the agency's announcement. "If they test positive, carbamazepine should not be started unless the expected benefit clearly outweighs the increased risk of serious skin reactions."
The recommendation calls for with-holding carbamazepine based on the presence of the allele, not on a patient's racial identity. Rather, one's apparent racial classification is a factor in deciding whether he or she should receive the genetic test.
The FDA recommended that the test be performed for most patients of Asian ancestry because the broad categories of Asians carry wide variations of the relevant gene, and this particular mutation may be present in as many as 15 percent or more of the people in certain parts of China and southeast Asia, but as low as 1 percent or less in Japan and Korea.
Scientists have pointed out that racial and ethnic classifications are not precise reflection of genetic make-up of a person, and the FDA recommendations specifically pointed out the "difficulty in ascertaining ethnic ancestry and the likelihood of mixed ancestry."
The agency's recommendations also note that not all patients positive for HLA-B*1502 will develop Stevens Johnson syndrome or toxic epidermis necrolysis, and those who have tolerated carbamazepine for several months should be considered relatively safe from the reactions even if they carry the genetic marker and regardless of ethnicity.
As scientists identify more genetic variations and their physiologic effects, the risks and benefits of more drugs will become better defined, and patients with high risk of side effects or high likelihood for responding to a medication will be better identified.
In 2007, National Institute of Mental Health scientists found two genetic variations that significantly influence the emergence of suicidal thoughts upon starting citalopram, a selective serotonin reuptake inhibitor (Psychiatric News, October 19, 2007).
Pharmacologists have long been aware of variations in liver-enzyme genes that can affect how fast or slow drugs are metabolized in the body and are more frequently present in certain ethnic groups. These variations can lead to substantial differences in side effects and sometimes effectiveness, of the same dose of a drug in individual patients.
Since the FDA's 2004 approval of a genetic test, AmpliChip Cytochrome P450 Geno-typing, for detecting mutations that affect antidepressants, antipsychotics, and many other drugs, genetic concerns have gradually increased.
For example, the FDA has issued warnings that some women with certain gene variations in liver enzymes that convert codeine into morphine more rapidly than most others may excrete unusually high levels of morphine in their breast milk and risk overdose when breast-feeding.
In August 2007 the labeling information for warfarin was updated and approved by the agency that recommends genetic tests to predict patients' variable response to the drug's effect on preventing blood clots.
"Driven by advances in genomics, emerging insight into each individual's unique susceptibility to disease promises to transform patient care," wrote James Evens, M.D., Ph.D., an associate professor in the Department of Genetics at the University of North Carolina, in a commentary in the December 12, 2007, JAMA.
He argued that the growing knowledge in genetics will inevitably change medicine and the health care delivery system in a fundamental way.
Pharmacogenomics, the study of how individual genetic variations affect people's response to drug therapy, will be increasingly applied in practice and change the "current practice of broad, somewhat random prescribing of a medication to everyone with a given disorder." Posts: 590 | From Canada | Registered: Oct 2007
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luvs2ride
Frequent Contributor (1K+ posts)
Member # 8090
posted
This is excellent news!
Insurance companies should not be allowed to drop you because you are genetically suspectable to a certain illness. Rather, knowledge of this susceptability will allow the patient to practice healthy avoidance techniques and the doctor will avoid medications that increase the risk.
My recent genetic profile shows I am unable to detox certain toxins from my body. For example: plastics.
I've been thinking about this and wondering "Whose DNA is programed to detox plastics? or exhaust fumes? How long have plastics and exhaust fumes been around? How long would it take the human body to evolve to include DNA that can detox these substances?
I also can't detox pesticides, herbicides and most medications. How long have they been around?
I would guess probably a majority of people can't genetically detox these substances and any other substances that have been around less than 100 yrs.
Seems to me lots of people would have a problem detoxing synthetic materials that have been around less than 100 yrs.
-------------------- When the Power of Love overcomes the Love of Power, there will be Peace. Posts: 3038 | From america | Registered: Oct 2005
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Truthfinder
Frequent Contributor (1K+ posts)
Member # 8512
posted
Very good find, Looking!
This is certainly good news - a step in the right direction, I hope.
-------------------- Tracy .... Prayers for the Lyme Community - every day at 6 p.m. Pacific Time and 9 p.m. Eastern Time � just take a few moments to say a prayer wherever you are�. Posts: 2966 | From Colorado | Registered: Dec 2005
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lymie_in_md
Frequent Contributor (1K+ posts)
Member # 14197
posted
Absolutely, great find!
Hopefully this opens the door someday toward genetic profiling of all americans as a matter of long term health and covered by insurance. Not that I think it will happen to soon, but hopefully it will help future generations.
One thing I was wondering, genetic testing prior to the administration of vaccines, wouldn't that be a good idea? Especially in the area of detoxification.
Thanks to LUV2RIDE, I'm definitely going to ask my doctor about genetic testing.
-------------------- Bob Posts: 2150 | From Maryland | Registered: Dec 2007
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TerryK
Frequent Contributor (5K+ posts)
Member # 8552
posted
Thanks for posting this.
I think that genetic testing will be very helpful for treatment decisions and even prevention but there would need to be some strict regulations governing it's use since it could turn into genetic profiling by insurance companies, employers etc..
For example, if it were determined that you have a genetic propensity towards certain types of cancers (as my sister found out), and that info was available to insurance companies, guess who would have trouble finding an insurance company who would cover her?
Terry
Posts: 6286 | From Oregon | Registered: Jan 2006
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map1131
Frequent Contributor (5K+ posts)
Member # 2022
posted
Great reading Looking. Reminds me of some things Gigi used to post.
One man's medicine is another man's poison.
I sure do miss the Gigi postings? Anyone else? She was a very wise woman in many ways. I still have a posting from her back in '03, that I printed off.
I'm going to dig through my folders of info and find it and post the list of all her protocols she used in 5 yrs+ to rid herself and her husband of lyme & company.
Maybe I should look in archives and see if it's still there on lymenet somewhere.
Pam
-------------------- "Never, never, never, never, never give up" Winston Churchill Posts: 6478 | From Louisville, Ky | Registered: Jan 2002
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