Also indexed as: Nolvadex
Tamoxifen is an antiestrogen drug primarily used to treat women with breast cancer or possibly to help prevent breast
cancer in women at high risk. It is also used to treat mastalgia (painful breasts) and
gynecomastia (abnormal breast enlargement in males).
Interactions with Vitamins, Herbs, and Foods
In some cases, an herb or supplement may appear in more than one category, which may seem
contradictory. For clarification, read the full article for details about the summarized
| May Be Beneficial: Supportive
interaction—Taking these supplements may support or otherwise help your medication
Gamma linolenic acid (GLA)
Avoid: Adverse interaction—Avoid these supplements when taking this
medication because taking them together may cause undesirable or dangerous results.
Citrus flavonoids (tangeretin)
|Depletion or interference
|Side effect reduction/prevention
An asterisk (*) next to an item in the summary indicates that the
interaction is supported only by weak, fragmentary, and/or contradictory scientific
Interactions with Dietary Supplements
Preliminary research in animals found that the citrus flavonoid tangeretin (found primarily in
the peel of citrus fruits) interferes with the ability of tamoxifen to inhibit tumor
growth.1 Although the evidence is far from conclusive, people taking tamoxifen
should probably avoid citrus bioflavonoid supplements, as well as beverages and foods to which
citrus peel oils have been added.
Gamma-linolenic acid (GLA), found in evening
primrose and borage oils, may enhance the
therapeutic effects of tamoxifen. A small group of breast cancer patients took 2.8 g of oral
GLA per day in addition to tamoxifen, in a preliminary trial.2 Another group of
breast cancer patients took tamoxifen alone. Those taking the GLA-tamoxifen combination
appeared to have a better clinical response than did those taking tamoxifen alone. However,
the results of this preliminary research are far from conclusive and need to be confirmed in a
larger, more definitive trial.
In preliminary research, large amounts of melatonin were used successfully in combination with
tamoxifen in a few people with breast cancer
for whom tamoxifen had previously failed.3 The amounts used in this study should be
taken only under the supervision of a doctor.
Tocotrienols are compounds similar to vitamin
E that are found in palm oil. Test tube studies have shown that tocotrienols enhance the
effects of tamoxifen.4 Controlled studies are needed to determine whether
supplementing with tocotrienols might enhance the anticancer effects of tamoxifen.
1. Bracke ME, Depypere HT, Boterberg T, et al. Influence of tangeretin on
tamoxifen’s therapeutic benefit in mammary cancer. J Natl Cancer Inst
2. Kenny FS, Pinder SE, Ellis IO, et al. Gamma linolenic acid with
tamoxifen as primary therapy in breast cancer. Int J Cancer 2000;85:643–8.
3. Lissoni P, Barni S, Meregalli S, et al. Modulation of cancer endocrine
therapy by melatonin: A phase II study of tamoxifen plus melatonin in metastatic breast cancer
patients progression under tamoxifen alone. Br J Cancer 1995;71:854–6.
4. Guthrie N, Gapor A, Chambers AF, Carroll KK. Inhibition of
proliferation of estrogen receptor-negative MDA-MB-435 and -positive MCF-7 human breast cancer
cells by palm oil tocotrienols and tamoxifen, alone and in combination. J Nutr