questions about tamoxifen. .......

michelleLg

I was just put on tamoxifen on Wednesday. I was doing some research online and saw some info about tamoxifen and paxil and then WHAM I was hit with loads of articles about paxil causing tamoxifen to not be as effective. I was put on 25mg of paxil 7 yrs ago and now I am on panic mode. I'm going to call my doctor on Monday but does anyone have info or similar experience they could share. I can't believe there is so much info on it and nothing was said by my pharmacist or oncologists. I fear hat even i go off of it asap , that will stay in my system and still cause problems.

living

Hello,

I was on Wellbutrin for years, when I was dx with breast cancer, I did some reading about Tamoxifin. Found out that the two wouldn't go together. talked to Dr. and went on Effexor XL 75 mg three times a day. as a bonus it helps with hot flashes. hope you do well

michelleLg

Thankyou. I was just surprised to find out on the Internet first, and there is so much info. Just couldn't understand why I wasn't told but I'm calling Monday and I'm switching asap. 😊

Anonymous

MichelleLg, I think Tamoxifen and the SSRIs like Paxil, use the same pathways and therefore are not compatible.  Since they share those same pathways it makes both of them less effective.  At least that is what my onc told me years ago.  Please let us know what you find out. 

Anonymous

I think Paxil is one of the ones that can't be used with tamoxifen; they usually switch you over to Effexor. Paxil takes about 4-6 weeks to get fully out of your system.

anne

besa

. As Jillian777 explained tamoxifen is converted to a more active form (when it comes to bc prevention and treatment) called "endoxifen" by an enzyme CYP2D6 in the liver. Some antidepressants are also metabolized by the same CYP2D6 enzyme. The thought is that if the CYP2D6 enzyme is being used to metabolize the antidepressant-- enough of the enzyme won't be available to do a good job of converting tamoxifen to endoxifen.

The first link is to  an older paper that explains how they think tamoxifen is metabolized. The part of this paper that talks about genotype and tamoxifen metabolism is controversial... see the breast cancer.org link at the bottom of this post. 

http://jop.ascopubs.org/content/1/4/155.full

http://www.breastcancer.org/research-news/earlier-research-on-cyp2d6-may-be-flawed

michelleLg

Thankyou. On my way to the doc now, armed with this info.