The bmj have just published a study that showing that tamoxifen may not prevent breast cancer if women also take the antidepressant Seroxat (paroxetine). This only applies to the Seroxat, other antidepressants did not have this effect. It seems that Seroxat reduces or completely stops the benefit of tamoxifen. The full (technical) article is here, there is also a short video with one of the researchers on Insider Medicine.
If I get a chance I’ll write a longer article explaining why Seroxat in particular may be having this effect, basically in order to work your body needs to break tamoxifen down into two different parts, tamoxifen is broken down by something called P450, more specifically P450 isoenzyme 2D6 (or CYP2D6 for short). Unfortunately Seroxat works (at least in part) by STOPPING CYP2D6 from working, so this means that tamoxifen can’t get broken down into the two different parts that are needed to block the oestrogen receptor and prevent cancer cells growing.
This is interesting research, it tells us something we didn’t know and it tells us something useful. Other anti-depressants don’t inhibit CYP2D6, so there are other treatments available for people who need an anti-depressant and are taking tamoxifen.