I am being treated for breast cancer with tamoxifen. I have also have experienced depression but have been told that I cannot take certain antidepressants. Why do I need to be concerned about antidepressants while taking tamoxifen?
Tamoxifen is an estrogen receptor blocker used for breast cancer (blocking breast tumor growth) and is converted to active metabolites through a liver enzyme.
In other words, it needs to be broken down in the liver for it to be activated, somewhat like needing to strike a match for it to produce fire.
Strong inhibitors of this activating enzyme include, in order, the antidepressants paroxetine (Paxil), fluoxetine (Prozac), bupropion (Wellbutrin), duloxetine (Cymbalta) and sertraline (Zoloft).
By slowing the activity of the enzyme, these antidepressants may decrease the conversion of tamoxifen to its active metabolites (especially endoxifen, which is 30 to 100 times more potent than tamoxifen for suppressing breast cancer cell growth) and decrease the effectiveness of tamoxifen.
A study of women with breast cancer, published in 2010 in the journal Psychiatry, compared 945 women taking tamoxifen alone with 353 women taking tamoxifen with paroxetine, fluoxetine or sertraline.
The women taking those antidepressants with tamoxifen were almost twice as likely (14 percent versus 7.5 percent) to experience a cancer recurrence over an average of 340 days.
Antidepressants that do not have this suppressing effect on the breakdown of tamoxifen include citalopram (Celexa), escitalopram (Lexapro), venlafaxine (Effexor) and desvenlafaxine (Pristiq).
We prefer to use these antidepressants for women who are enduring clinically significant depression while recovering from breast cancer treated with tamoxifen.