Patients with variant forms of the gene CYP2D6 may not receive full benefit from<unk>  because of too slow metabolism of the<unk>  prodrug into its active metabolites. On 18 October 2006, the Subcommittee for Clinical Pharmacology recommended relabeling<unk>  to include information about this gene in the package insert. Certain CYP2D6 variations in breast cancer patients lead to a worse clinical outcome for<unk>  treatment. Genotyping therefore has the potential for identification of women who have these CYP2D6 phenotypes and for whom the use of<unk>  is associated with poor outcomes. Recent research has shown that 7–10% of women with breast cancer may not receive the full medical benefit from taking<unk>  due to their genetic make-up. DNA Drug Safety Testing can examine DNA variations in the CYP2D6 and other important drug processing pathways. More than 20% of all clinically used medications are metabolized by CYP2D6 and knowing the CYP2D6 status of a person can help the doctor with the future selection of medications. Other molecular biomarkers may also be used to select appropriate patients likely to benefit from<unk> . Recent studies suggest that taking the selective serotonin reuptake inhibitors (SSRIs) antidepressants paroxetine (Paxil), fluoxetine (Prozac), and sertraline (Zoloft) can decrease the effectiveness of<unk> , as these drugs compete for the CYP2D6 enzyme which is needed to metabolize<unk>  into its active forms. A U.S. study presented at the American Society of Clinical Oncology's annual meeting in 2009 found that after two years, 7.5% of women who took only<unk>  had a recurrence, compared with 16% who took either paroxetine, fluoxetine or sertraline, drugs considered to be the most potent CYP2D6 inhibitors. That difference translates to a 120% increase in the risk of breast cancer recurrence. Patients taking the SSRIs; Celexa (citalopram), Lexapro (escitalopram), and Luvox (fluvoxamine), did not have an increased risk of recurrence, due to their lack of competitive metabolism for the CYP2D6 enzyme. A newer study demonstrated a clearer and stronger effect from paroxetine in causing the worst outcomes. Patients treated with both paroxetine and<unk>  have a 67% increased risk of death from breast cancer, from 24% to 91%, depending on the duration of coadministration.<unk>  interacts with certain other antiestrogens. The aromatase inhibitor aminoglutethimide induces the metabolism of<unk> . Conversely, the aromatase inhibitor letrozole does not affect the metabolism of<unk> . However,<unk>  induces the metabolism of letrozole and significantly reduces its concentrations.
Tamoxifen
Endoxifen
N-Desmethyltamoxifen
Anastrozole
Salvestrol
Bazedoxifene
N,N-Didesmethyltamoxifen
Exemestane