Dr. Patricia Yarberry Allen is a collaborative physician who writes a weekly “Medical Monday” column for Women’s Voices for Change.  (Search our archives for her posts, calling on the expertise of medical specialists, on topics from angiography to vulvar melanoma.)

This week, Dr. Pat has asked Megan Riddle, M.D./Ph.D., a psychiatry resident at the University of Washington and a graduate of the Weill Cornell/Rockefeller/Sloan-Kettering Tri-Institutional MD-PhD Program, to address the concerns of a woman who is taking tamoxifen and wonders how that affects her disturbing menopausal mood swings.

Dear Dr. Pat:

I had breast cancer two years ago. It was found early, and I had a lumpectomy and radiation postoperatively. I am taking tamoxifen, since the cancer was strongly estrogen-positive.  My last period was one year ago, and I am now 50.  

I can manage the hot flashes, since they aren’t so frequent, and frankly aren’t nearly as bad as I had thought they would be. However, I have real mood issues that I can’t afford, since I need my job and would like to stay married.  I used to have symptoms like these before my period—really nasty mood swings for 24 hours.  Now I cry, lose my temper often, and am unpredictably agitated and anxious. I am no longer sleeping for more than four hours, and when I wake up I have a lot of trouble getting back to sleep because I start to worry and think about all the things that are going wrong in my life. Actually, I don’t have a bad life, so this is troubling as well. I used to be an optimistic person, so this new person I have become is hard for me to live with.

Sarah

Dr. Riddle Responds:

Dear Sarah:

I am glad to hear that your cancer was found early and that you are now in remission, but am sorry to hear that you are struggling with your mood. Cancer can take a significant toll on your emotional health, for a number of reasons. Up to one in four individuals with cancer develops depression, which can seriously impact quality of life even as the cancer goes into remission.

Furthermore, sometimes the treatments themselves can influence your moods. For tumors like yours that are responsive to estrogen, drugs that block estrogen activity in breast tissue can play a critical role in treatment. While some studies report that these drugs do not tend to influence mood, you certainly would not be the first woman to find that they can lead to mood swings and increased irritability.

The good news is that we have treatment options. Many women find that antidepressants are useful in dealing with these symptoms. It is important, however, that the doctor who prescribes your antidepressant is aware you are taking tamoxifen. For tamoxifen to work, your liver must break it down to its active form, using a specific enzyme called CYP2D6. Some popular antidepressants such as paroxetine (Paxil), fluoxetine (Prozac), and bupropion (Wellbutrin), suppress the activity of this enzyme. This means that these medications will make the tamoxifen less effective, and so they should be avoided. Studies have borne this out, showing increased risk of death from breast cancer in individuals who take tamoxifen and Paxil.

Instead, the antidepressants venlafaxine (Effexor) and desvenlafaxine (Pristiq) have been shown to have little effect on the CYP2D6 enzyme and are thus good choices for those taking tamoxifen. In addition to improving mood, these medications have been shown to be helpful in reducing hot flashes, thus providing additional benefit in treating the side effects of tamoxifen.

Your oncologist may be able to recommend a psychiatrist experienced in treating individuals with cancer. Many cancer treatment centers have psychiatrists on staff specifically to work on addressing the mental health component of cancer care. Please reach out to your current provider.

References

Desmarais, J. E., & Looper, K. J. (2010). Managing menopausal symptoms and depression in tamoxifen users: implications of drug and medicinal interactions. http://www.ncbi.nlm.nih.gov/pubmed/20880642 Maturitas, 67(4), 296-308.