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

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.

Comments

  • camul
    camul Member Posts: 2,537
    #2
    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
    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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