Anastrozole; Letrozole/Tamoxifen
This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.
Medical warning:
Severe. These medicines may interact and cause very harmful effects and are usually not taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.
How the interaction occurs:
Tamoxifen may speed up how quickly your liver processes anastrozole and letrozole.
What might happen:
The beneficial effects of anastrozole and letrozole may decrease.
What you should do about this interaction:
Let your healthcare professionals (e.g. doctor or pharmacist) know that you are taking these medicines together.Your healthcare professionals may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.
References:
1.Arimidex (anastrozole) US prescribing information. AstraZeneca Pharmaceuticals LP April, 2011.
2.Dowsett M, Pfister C, Johnston SR, Miles DW, Houston SJ, Verbeek JA, Gundacker H, Sioufi A, Smith IE. Impact of tamoxifen on the pharmacokinetics and endocrine effects of the aromatase inhibitor letrozole in postmenopausal women with breast cancer. Clin Cancer Res 1999 Sep;5(9):2338-43.
3.Nolvadex (tamoxifen citrate) US prescribing information. AstraZeneca Pharmaceuticals LP March, 2006.
4.Weiss L. Personnal communication. Novartis Pharmaceuticals Corporation January 3, 2002.
5.Femara (letrozole) US prescribing information. Novartis Pharmaceuticals Corporation December, 2011.
6.Ingle JN, Suman VJ, Johnson PA, Krook JE, Mailliard JA, Wheeler RH, Loprinzi CL, Perez EA, Jordan VC, Dowsett M. Evaluation of tamoxifen plus letrozole with assessment of pharmacokinetic interaction in postmenopausal women with metastatic breast cancer. Clin Cancer Res 1999 Jul;5(7):1642-9.
