If you're taking medications -- for example, a selective serotonin reuptake inhibitor (SSRI) such as fluoxetine (Prozac) or paroxetine (Paxil) -- or other antipsychotic or cardiac drugs and you're a female patient taking tamoxifen, you may want to schedule an appointment with your doctor very soon.
The problem: Some drugs suppress the presence of the CYP2DG enzyme, a critical trigger that allows the liver to convert tamoxifen into the more active endoxifen that, in turn, may prevent breast cancer or a repeat battle with this frightening disease.
Follow-up research to previous studies conducted at the Mayo Clinic College of Medicine that identified fluoxetene and paroxetene as potentially harmful for breast cancer patients taking tamoxifen has expanded the list of drugs inhibiting CYP2D6 levels to include drugs that treat infectious diseases, depression, psychosis and heart problems. (Check the Medscape link below for a full list of drugs that affect CYP2DG levels and many alternatives.)
As a result of this research, the Mayo Clinic has been testing breast cancer patients for the CYP2DG enzyme before prescribing tamoxifen in excess of three years, considered a controversial practice among some experts.
Still, there's no question, avoiding drugs that interact poorly with tamoxifen is the best course of action for patients taking tamoxifen. For your own peace of mind, however, PLEASE do your homework and talk to your doctor before making any changes to your treatment regimen.
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Journal of Clinical Oncology, Vol. 28, No. 16, pp. 2768-2776, June 1, 2010
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