Any one else on levothyroxine (synthroid) and arimidex (or femara or armoasin)?

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CypressCynthia
CypressCynthia Member Posts: 4,014 Member
in Breast Cancer #1
It appears that my endocrinologist and I have noticed a drug-drug interaction between synthroid and arimidex. I am hypothyroid and had been on the same 0.15 mg/day dose for >20 years.

When I started arimidex, I began to be hyperthyroid and we slowly lowered my synthroid dose all the way down to 0.088 mg/day until I was normal again. In August, I discontinued Arimidex when I started Faslodex and now I am very hypothyoid again.

My suspicion is that I will end up back on my usual old dose of 0.15mg/day again, but I have to be titrated up slowly to watch for cardiac effects.

I'll keep you posted, but wanted to let others know that my endocrinologist and I suspect that the aromatase inhibitor (arimidex, femara, aromasin) may make the levothyroxine more bioavailable. If you are on the combination of drugs, please have your physician check your TSH regularly.

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  • camul
    camul Member Posts: 2,537
    #2
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    Hi CC
    I am on Synthroid and found an interaction between that and Evista. I researched it online until I found a site that showed an interaction. My levels dropped and I became hypo again. Went to the endo and she agreed that there could be an interaction, upped the level for a bit. Changed the time frame btwn taking the meds. I am back my normal dose. I now take the thyroid meds in the a.m. and take the Evista 10 -12 hours later. My thyroid is now back in the normal range.

    I can always tell when it goes off, as I get really emotional and cry over almost anything which is not at all me....

    Thanks for this info. I couldn't find any posts on here where others had experienced the same.

    Carol
  • VickiSam
    VickiSam Member Posts: 9,079 Member
    #3
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    camul said:

    Hi CC
    I am on Synthroid and found an interaction between that and Evista. I researched it online until I found a site that showed an interaction. My levels dropped and I became hypo again. Went to the endo and she agreed that there could be an interaction, upped the level for a bit. Changed the time frame btwn taking the meds. I am back my normal dose. I now take the thyroid meds in the a.m. and take the Evista 10 -12 hours later. My thyroid is now back in the normal range.

    I can always tell when it goes off, as I get really emotional and cry over almost anything which is not at all me....

    Thanks for this info. I couldn't find any posts on here where others had experienced the same.

    Carol

    I was instructed about 20 years ago ... to supplement
    my diet with calcium vitamins .. due to my daily synthroid medication. Fortunately, I am NOT on any hormones, as I was ER/PR negative (bad thing, herceptin for 1 year).

    The fun, and side efforts seem to never stop ... Thank God, we are educated Women who feel the need to know!!!!

    Strength, Courage and Hope.

    Vicki Sam

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