I thoroughly enjoyed the opportunity to talk to the breast cancer support group at the Jewish Family Services Center here in Dallas this week. This was my second visit with them and again I was impressed by the intelligence, passion and generosity of the women who are drawn to this program. This time I was introducing the idea of an integrated approach to anxiety and depression. According to the National Institute of Mental Health, the prevalence of depression in the general population in 2008 (the latest year for which statistics are available) is 6.7% of the adult population and the prevalence in women is 8.1%. Adding the diagnosis of breast cancer understandably bumps the prevalence slightly higher.

I reviewed the current pharmaceutical and nutraceutical approaches to depression and anxiety and also led the group through some paced breathing and the quick coherence technique of HeartMath. One woman announced that the breathing exercise made her feel calmer than she’d been all day!

During the discussion, one women raised the question about Tamoxifen and anti-depressants. Her oncologist told her that only a few anti-depressants could be prescribed to women on Tamoxifen. Since this is relatively new information, I’ve been researching the claim for the group and decided to post my findings here in the blog.

The concern stems from a study done in Ontario that was published in the British Medical Journal (Kelly CM et al. BMJ 2010 Feb 8:340). This reference is available on PubMed. The researchers looked at women over 66 who were on Tamoxifen and found that the mortality rate was higher in women on Paxil (paroxetine) versus some of the other antidepressants. The reason appears to be that Tamoxifen is broken down in our livers by an enzyme called cytochrome P450 2D6 (the name of this enzyme is often shortened to cyp2D6). Some medications including Paxil are also broken down by cyp2D6. If someone has a genetic variation such that this enzyme is not as efficient, they are often called poor metabolizers. This genetic variation is called a “snip” for the abbreviation single nucleotide polymorphism. If they are poor metabolizers, they will be unable to break down the Tamoxifen effectively and its benefit will be “blocked” by medications that use this pathway. (sort of like musical chairs and everyone is competing for the same seat) Paxil is metabolized by this pathway, so is Thorazine, Prozac, miconazole (a yeast medicine), and quinidine – to name just a few. If a medication has no inhibition or a weaker inhibition of cyp2D6, the Tamoxifen will be broken down more efficiently – for that reason the authors suggest Celebrex or Lexapro because they don’t compete as strongly for cyp2D6.

I read a review article by Kathleen Pritchard which was published in Breast Cancer Research Vol 12 Supp 4 (also on PubMed) and she notes that there are studies that refute the claim – one from Denmark, for example, and states that the final answer isn’t really known as far as SSRI’s and Tamoxifen. Some people are suggesting that we should test the urine for endoxifen (a break down product of Tamoxifen) and make sure that the drug is being effectively metabolized. This isn’t the standard of care as yet, nor is checking women to see if they have genetic SNP’s in their detox genes.

I’ve done the gene testing on people if they note a lot of side effects from a long list of medicines or if we’re suspicious of a problem. The testing is fairly expensive ($500 to $1000 depending on which genes we test) and is NOT covered by insurance. Another wrinkle in the discussion, whenever genetic screening comes up, is how likely is a SNP? We know from population studies of the SNP’s for cyp2D6 that about 6% of Caucasians are “poor metabolizers” of this gene. Other ethnic groups show poor metabolizer rates of 3.3% (Black North Americans), 8.4% (French), 7.7% (Southern Germans) and practically 0% in Korean and Chinese populations.

So, the take home message is Tamoxifen and anti-depressants can mix – but choosing a medicine that is less likely to interrupt the enzyme cyp2D6 is probably a good idea. Or better yet, learn coherence training and get regular acupuncture treatments!

Until next time, be well!