After being told by my surgeon that at some point through my treatment I would be prescribed Tamoxifen & because I take several other medications which include antipsychotics, antidepressants & tablets for anxiety, I decided to research whether my other medications would work well with Tamoxifen & the side effects of Tamoxifen.
There are lots of medical journals & research papers that can be accessed on the internet so I spent some time researching & found most of my information on American medical sites. I was looking for information on drug interactions & stumbled across an article in the Pharmacy Times which read: Beware of CYP2D6 inhibitors in patients taking Tamoxifen.
CYP2D6 is an enzyme & there are many drugs (many of which are antidepressants) that can & do, substantially inhibit CYP2D6. CYP2D6 activity is an important factor in the effectiveness of Tamoxifen treatment; if a medication you take, inhibits the activity of CYP2D6 then that in turn inhibits the effect of Tamoxifen, which considering the reason you are taking Tamoxifen, you would not want to take any other medication that would hinder how well it worked.
I discovered that one of my medications, namely, Duloxetine, is a known inhibitor of the effectiveness of Tamoxifen & I continued to read many medical reports that confirmed this. For me this was something I needed to sort out pretty quickly; I knew I needed Duloxetine as I took it to help with my depression but I also knew it could be changed for a different type of antidepressant that did not affect the way that Tamoxifen worked.
So armed with my information I booked an appointment with my GP, he listened to what I had researched, checked on his computer database, that all GP's have access to, & promptly told me that he could not see any evidence to confirm my research, I explained that most of my research was based on the findings of medical journals from the USA to which he replied that he complied to the medical UK database guidelines & as far as he was concerned I had no need for concern & sent me on my way.
I was more than annoyed but persisted with the issue when I next met with my oncologist who prescribed Tamoxifen (for 10 years), the oncologist also dismissed my research & worries after a quick check on his database. I insisted that I did not want to risk taking a medication that some researchers believed significantly reduced the effectiveness of Tamoxifen, but he just told me I was worrying over nothing & all would be fine.
So I headed home defeated & seriously considered taking myself off the Duloxetine & risking my depression getting worse; I was already tormenting myself with thoughts of the cancer returning so really did not want anything to stop Tamoxifen working, if Tamoxifen could help me. One of the side effects of Tamoxifen is low mood, so as I already suffer from unusually low mood, stopping my antidepressants could have a devastating effect.
I made the decision to book an appointment with a prescribing psychiatric nurse who works at my nearest mental health unit; I booked a medication review. The psychiatric nurse looked at my research & took the time to do an internet search on his mobile phone whilst with me, he was shocked to see that my research had been correct but also very interested as he had not before come across this particular conflict of medications. He then messaged a pharmacist colleague concerning the research & the pharmacist messaged back confirming that she had read in many medical journals that some drugs including Duloxetine, hindered the effectiveness of Tamoxifen.
Finally I had found someone who not only listened but realised that my medication needed to be changed in order to ensure Tamoxifen could work for me in the best possible way. My Duloxetine was changed to a drug called Escitalopram, which is not known to block Tamoxifen. I now feel more at peace that I have done all I can in the hope that Tamoxifen has the best chance of working as effectively as possible for me, although I'm still rather upset & disappointed that both a GP & oncologist dismissed this important fact.
Other medications that were listed as inhibiting the effectiveness of Tamoxifen are: Amiodarone, Bupropion, Chlorpheniramine, Chloroquine, Chlorpromazine, Cinacalcet, Diphenhydramine, Fluoxetine, Halofantrine, Haloperidol, Imatnib, Paroxetine, Perphenazine, Propafenone, Propoxyphene, Quinacrine, Quinidine, Quinine & Terbinafine.
