Metabolize test for Tamoxifen? What is that?

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Jeanne D
Jeanne D Member Posts: 1,867
edited March 2014 in Breast Cancer #1
I have read on here somewhere where some of you talked about a test to take to see if tamoxifen would work on you or something? What is the test? I haven't heard of this, nor, have I been told about it from my oncologist. thanks!

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  • EveningStar2
    EveningStar2 Member Posts: 491 Member
    #2
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    blood test
    When I saw the medical oncologist, she wanted to put me on tamoxifen but wanted to make sure that I could metabolize it. I had blood drawn and the office called me about a week later to say that I could metabolize it and to take the drug as scheduled. I got the insurance stuff yesterday--darn it it doesn't state what the test was. But they charge $989 for it without insurance!

    Maureen
  • Noel
    Noel Member Posts: 3,095 Member
    #3
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    I don't know, but, I would
    I don't know, but, I would like to know too. As, I am supposed to take it too after my radiation treatments are finished.
  • tlmac
    tlmac Member Posts: 272 Member
    #4
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    Metabolizing Tamoxifen
    Here's a link to an article that explains the test. You may have to copy the link and paste it in the address window of your browser. I believe it will answer your questions.
    http://www.dslrf.org/breastcancer/content.asp?CATID=19&L2=3&L3=7&L4=0&PID=&sid=132&cid=1146
  • Noel
    Noel Member Posts: 3,095 Member
    #5
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    tlmac said:

    Metabolizing Tamoxifen
    Here's a link to an article that explains the test. You may have to copy the link and paste it in the address window of your browser. I believe it will answer your questions.
    http://www.dslrf.org/breastcancer/content.asp?CATID=19&L2=3&L3=7&L4=0&PID=&sid=132&cid=1146

    Thanks Tlmac..I will look
    Thanks Tlmac..I will look that site over.
  • EveningStar2
    EveningStar2 Member Posts: 491 Member
    #6
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    tamoxifen & grapefruit
    One more d**n thing to be aware of: it is known that grapefruit consumption interferes with one of the enzymes that metabolize certain drugs. Some think tamoxifen is one, some don't. I've been searching the net and have gotten both answers so, ask your doctor.
  • mimivac
    mimivac Member Posts: 2,143 Member
    #7
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    EveningStar2 said:

    tamoxifen & grapefruit
    One more d**n thing to be aware of: it is known that grapefruit consumption interferes with one of the enzymes that metabolize certain drugs. Some think tamoxifen is one, some don't. I've been searching the net and have gotten both answers so, ask your doctor.

    Tamoxifen and other drugs
    Yes, and there are other drugs as well (including some anti-depressants) that may interfere with Tamoxifen metabolization. Ask your onc. if you are on any other medications.
  • Jeanne D
    Jeanne D Member Posts: 1,867
    #8
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    mimivac said:

    Tamoxifen and other drugs
    Yes, and there are other drugs as well (including some anti-depressants) that may interfere with Tamoxifen metabolization. Ask your onc. if you are on any other medications.

    Thank you all!
    I am on an anti-depressant and a nerve pill. But, my oncologist knows. However, I am going to change oncologist's. I really don't like the one that I have, nor, do I trust her.
  • phoenixrising
    phoenixrising Member Posts: 1,508
    #9
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    Hi Jeanne, I had the test
    Hi Jeanne, I had the test done last year when I was having a problem with Tamoxifen. My oncs were not familiar with it but there has been a lot of press coverage since the Mayo Clinic through their research are now recommending all women have the test done before starting Tamoxifen. This came out of the last San Antonio Breast Cancer Symposium. Some oncs don't think it's reliable and some automatically check and think it's the way to go. There is a common thought that if you have se then it must be working. However the New York Times interviewed a woman who went through horrific se and found out she was a poor metabolizer. Another thought is some oncs don't want to have the test done if the woman is premenopausal because there are no other options other than having ovaries removed which would then qualify her for an AI. That one doesn't make sense to me but that is what sometimes happens.

    Tamoxifen needs to be converted to Endoxifen in order to be effective and the enzyme responsible for this conversion is created by the cyp2D6 isoform. Cyp2D6 is responsible for the metabolism of ~25% of pharmaceuticals. There are many cyp's, but 2D6 is commonly known as the primary isoform to metabolize Tamoxifen. The numbers may vary depending on where you look but about 7-10% of the population is a poor metabolizer which means they will gain little benefit from drugs metabolized by cyp2D6. I am an intermediate metabolizer which means one out of two alleles are faulty or non functioning. Actually there is supposed to be a black box warning on Warfarin (blood thinner) indicating there could be an adverse reaction for those who have dysfunctional genes.

    For more info on this (and probably more correct) you can check with a couple of labs that do the test. I had mine done at www.healthanddna.com (Genelex), others have used www.dnadirect.com and of course you can do a search at the Mayo Clinic.

    This has been quite a topic at www.breastcancer.org (just do a search for cyp2D6) and this is the address for the flockhart charts that show what metabolizes what and includes inhibitors like SSRI antidepressants and inducers.

    http://medicine.iupui.edu/Flockhart/table.htm

    I hope I have been helpful.
    love
    jan

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