Drug Interactions:
Estrogen

Estrogen is used as a component of birth control pills as well as for preventing osteoporosis and heart disease in menopausal women.

Some estrogen products contain the hormone in different forms. For example, certain products such as Ortho Dienestrol Vaginal Cream contain estrogen as dienestrol. Medications containing a form of estrogen called estradiol include:

• Alora
• Climara
• Combipatch
• Delestrogen (injectable)
• depGynogen (injectable)
• Depo-Estradiol Cypionate (injectable)
• Depogen (injectable)
• Esclim
• Estrace
• Estraderm
• Estra-L (injectable)
• Estring
• Fempatch
• Gynogen L.A. (injectable)
• Vagifem
• Valergen (injectable)
• Vivelle
• and others

Premarin, Cenestin, Prempro, and Premphase contain another form of estrogen called conjugated estrogens. Other forms of estrogen and some of their brand names include diethylstilbestrol diphosphate (Stilphostrol), estrone (Kestrone-5), esterified estrogens (Estratab, Menest), estropipate (Ogen, Ortho-Est), and ethinyl estradiol (Estinyl) among others.

Folate

Supplementation Possibly Helpful

Some evidence suggests that estrogen may interfere with the absorption of folate.¹ Since folate deficiency is fairly common even among those not taking estrogen, taking a folate supplement on general principle is probably a good idea.

Ipriflavone

Potential Benefits and Risks

When the two are taken together, ipriflavone may increase estrogen's ability to protect bone.^2–6 This may allow you to use a lower dose of estrogen and still receive its beneficial effects.

However, there may be risks involved. Although ipriflavone itself probably does not affect tissues other than bone, some evidence suggests that when it is combined with estrogen, estrogen's effects on the uterus are increased.^7,8 This might mean that risk of uterine cancer would be elevated by the combination.

It should be possible to overcome this risk by taking progesterone along with estrogen, which is standard medical practice in any case. However, this finding does make one wonder whether ipriflavone–estrogen combinations raise the risk of breast cancer as well, an estrogen side effect that has no easy solution. At present, there is no available information on this important subject.

Other Nutrients

Supplementation Possibly Helpful

Estrogen use may decrease blood levels of magnesium, vitamin C, and zinc.^9,10 This may mean that supplementation is advisable.

Boron

Theoretical Harmful Interaction

In some studies, boron has been found to elevate levels of the body's own estrogen.^11,12 This might lead to an increased risk of estrogen side effects if boron is combined with estrogen therapy.

Androstenedione

Theoretical Harmful Interaction

Androstenedione has become popular as a sports supplement, on the theory that it increases testosterone levels as well as sports performance. However, there is no evidence that it is effective. In addition, androstenedione appears more likely to elevate estrogen than testosterone levels. This could increase risks of developing estrogen-related diseases, including breast and uterine cancers. Women taking estrogen should not take androstenedione.¹³

Resveratrol

Possible Harmful Interaction

The supplement resveratrol has a chemical structure similar to that of the synthetic estrogen diethylstilbestrol and produces estrogenic-like effects.¹⁴ For this reason, it should not be combined with prescription estrogen products.

Indole-3-Carbinol

Theoretical Harmful Interaction

Indole-3-carbinol (I3C) is a substance found in broccoli that is thought to have cancer preventive effects. One of its mechanisms of action is thought to involve facilitating the inactivation of estrogen, as well as blocking its effects on cells.^17-20 The net result could be decreased effectiveness of medications containing estrogen.

Chasteberry

Theoretical Harmful Interaction

Because of its effects on the pituitary gland, chasteberry might unpredictably alter the effects of estrogen-replacement therapy.

Dong Quai

Interaction Unlikely or Probably Insignificant

The herb dong quai (Angelica sinensis) is used for menstrual disorders.

Because dong quai contains beta-sitosterol, a phytoestrogen,¹⁵ there have been concerns that taking the herb with estrogen might add to estrogen-related side effects. However, a 24-week placebo-controlled study of 74 postmenopausal women found no estrogen-like effects or reduction of menopausal symptoms associated with taking dong quai.¹⁶

Therefore, dong quai seems unlikely to increase estrogen-related side effects.

Last reviewed July 2002 by Medical Review Board

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