Tamoxifen drug interactions

You don't need to be Editor-In-Chief to add or edit content to WikiDoc. You can begin to add to or edit text on this WikiDoc page by clicking on the edit button at the top of this page. Next enter or edit the information that you would like to appear here. Once you are done editing, scroll down and click the Save page button at the bottom of the page.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Phone:617-525-6884

List of drug interactions

Coumarin-type anticoagulants

Cytotoxic agents

Antineoplastic drugs

Phenobarbital

Rifampin

Aminoglutethimide

Medroxyprogesterone

Bromocriptine therapy

---

Coumarin-type anticoagulants

When Tamoxifen is used in combination with coumarin-type anticoagulants, a significant increase in anticoagulant effect may occur. Where such coadministration exists, careful monitoring of the patient's prothrombin time is recommended. In the NSABP P-1 trial, women who required coumarin-type anticoagulants for any reason were ineligible for participation in the trial. Return to top

Cytotoxic agents

There is an increased risk of thromboembolic events occurring when cytotoxic agents are used in combination with Tamoxifen. Return to top

Antineoplastic drugs

Tamoxifen reduced letrozole plasma concentrations by 37%. The effect of Tamoxifen on metabolism and excretion of other antineoplastic drugs, such as cyclophosphamide and other drugs that require mixed function oxidases for activation, is not known. Tamoxifen and N-desmethyl Tamoxifen plasma concentrations have been shown to be reduced when coadministered with rifampin or aminoglutethimide. Induction of CYP3A4-mediated metabolism is considered to be the mechanism by which these reductions occur; other CYP3A4 inducing agents have not been studied to confirm this effect. Return to top

Phenobarbital

One patient receiving Tamoxifen with concomitant phenobarbital exhibited a steady state serum level of Tamoxifen lower than that observed for other patients (ie, 26 ng/mL vs. mean value of 122 ng/mL). However, the clinical significance of this finding is not known. Return to top

Rifampin

Rifampin induced the metabolism of Tamoxifen and significantly reduced the plasma concentrations of Tamoxifen in 10 patients. Return to top

Aminoglutethimide

Aminoglutethimide reduces Tamoxifen and N-desmethyl Tamoxifen plasma concentrations. Return to top

Medroxyprogesterone

Medroxyprogesterone reduces plasma concentrations of N-desmethyl, but not Tamoxifen. Return to top

Bromocriptine therapy

Concomitant bromocriptine therapy has been shown to elevate serum Tamoxifen and N-desmethyl Tamoxifen. Return to top

---

The content of this page is taken from the FDA package insert for this drug and should not be edited.