Drug & supplement interaction

Indole-3-carbinol + Segesterone Acetate, Ethinyl Estradiol

Segesterone Acetate, Ethinyl Estradiol brand name: Annovera.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Segesterone Acetate, Ethinyl Estradiol falls into 2 drug categories that Indole-3-carbinol can interact with; the most serious is rated moderate. Theoretically, indole-3-carbinol might increase the metabolism of CYP1A2 substrates and lower serum concentrations.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Indole-3-carbinol and Segesterone Acetate, Ethinyl Estradiol

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Indole-3-carbinol interacts with whole categories of medication. Segesterone Acetate, Ethinyl Estradiol falls into 2 of those categories, so it can interact with Indole-3-carbinol in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES

1 of 2

Why this applies to Segesterone Acetate, Ethinyl Estradiol

Segesterone Acetate, Ethinyl Estradiol falls under CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES — the group Indole-3-carbinol interacts with.

Theoretically, indole-3-carbinol might increase the metabolism of CYP1A2 substrates and lower serum concentrations.
Animal research shows that indole-3-carbinol induces CYP1A2 enzymes.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist with Annovera (the segesterone and ethinyl estradiol vaginal ring) and indole-3-carbinol. This supplement is thought to speed up a liver enzyme called CYP1A2, which helps clear the estrogen part of your ring. If that enzyme runs faster, estrogen levels could drop a bit, and in theory that might weaken how well the ring works or cause more breakthrough spotting and irregular bleeding.

I want to be honest about the evidence here: this is theoretical and based only on animal and lab data, not real-world cases with birth control. Eating broccoli or cabbage at dinner is not a concern. Concentrated supplement doses are the question mark. Since this ring is your contraception, it's worth a quick chat with your pharmacist or doctor before adding I3C.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. He YH, Friesen MD, Ruch RJ, Schut HA. Indole-3-carbinol as a chemopreventive agent in 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) carcinogenesis: inhibition of PhIP-DNA adduct formation, acceleration of PhIP metabolism, and induction of cytoch
Moderate

ESTROGENS

2 of 2

Segesterone Acetate, Ethinyl Estradiol also falls under ESTROGENS.

Indole-3-carbinol might interfere with the effects of estrogen therapy.
Preliminary clinical and in vitro evidence shows that indole-3-carbinol has antiestrogenic activity.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Annovera is a vaginal ring that releases two hormones, segesterone and ethinyl estradiol, to prevent pregnancy. The concern here is that indole-3-carbinol (I3C) may push back against estrogen activity in the body. In theory, that could blunt the estrogen part of your ring and might make side effects like breakthrough bleeding or spotting more likely.

I want to be honest about how soft this evidence is. It comes mostly from lab and animal work, not solid human studies, so we don't truly know if it weakens birth control in real life. Still, since reliable contraception matters, I wouldn't gamble on it. The amount of I3C you get from eating broccoli or cabbage is very unlikely to be a problem; concentrated supplements are the real question. Please check with your pharmacist or doctor before adding an I3C supplement.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Bell MC, Crowley-Nowick P, Bradlow HL, et al. Placebo-controlled trial of indole-3-carbinol in the treatment of CIN. Gynecol Oncol 2000;78:123-9. PubMed
  2. Kim, Y. S. and Milner, J. A. Targets for indole-3-carbinol in cancer prevention. J.Nutr.Biochem. 2005;16(2):65-73. PubMed
  3. Anon. Indole-3-carbinol. Monograph. Alternative Medicine Review 2005;10(4):337-42.
  4. McAlindon TE, Gulin J, Chen T, et al. Indole-3-carbinol in women with SLE: effect on estrogen metabolism and disease activity. Lupus 2001;10:779-83. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Indole-3-carbinol Also Interacts With Other Medications

Indole-3-carbinol has 293 moderate known drug interactions in our database — the Segesterone Acetate, Ethinyl Estradiol one above is among them. If you take anything else, check it against the full list below.

Moderate 293 No known interaction 2,537 (incl. Segesterone Acetate, Ethinyl Estradiol)
Taking anything else?

Check Another of Your Medications Against Indole-3-carbinol

Covers the 2,830 medications we’ve checked against Indole-3-carbinol. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Segesterone Acetate, Ethinyl Estradiol

This page covers Indole-3-carbinol only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Segesterone Acetate, Ethinyl Estradiol page lists 229 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Beer (major), Grapefruit (major), Siberian Cocklebur (major), St. John's Wort (major) and Wine (major).

By severity: 5 major · 193 moderate · 31 minor.

From our pharmacist’s overview on the Segesterone Acetate, Ethinyl Estradiol page

“St. John's wort is the interaction I would explain first to anyone using Annovera (segesterone acetate with ethinyl estradiol, a vaginal ring for birth control).”

Reviewed by 2 · Jul 18, 2026

Open the Segesterone Acetate, Ethinyl Estradiol interaction page

One more smart check

Taking Indole-3-carbinol as Part of a Dietary Supplement Product? Check It for Interactions

We hold 287 real supplement products containing Indole-3-carbinol, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Indole-3-carbinol. Your product may carry other ingredients that interact with Segesterone Acetate, Ethinyl Estradiol too, on top of Indole-3-carbinol — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Indole-3-carbinol and Segesterone Acetate, Ethinyl Estradiol Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Indole-3-carbinol
Top half

#391 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Segesterone Acetate, Ethinyl Estradiol
Top 25%

#409 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Indole-3-carbinol

What is Indole-3-carbinol?

  • Estrogen and hormone balance support
  • Breast and cervical health
  • Prostate health
  • Antioxidant and 'detox' support
  • General cancer-prevention interest

Indole-3-carbinol (I3C) is a compound formed when you eat cruciferous vegetables like broccoli and cabbage, and it is sold as a supplement mainly for hormone-related and cell-protective effects. Most human evidence is preliminary or comes from lab and animal studies, so it should not be relied on to prevent or treat any disease. Talk to your pharmacist or doctor before using it, and avoid it in pregnancy and breastfeeding.

Read the full Indole-3-carbinol monograph & all interactions
Keep checking

Other Drugs & Indole-3-carbinol

Browse every other medication we’ve checked against Indole-3-carbinol — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
293Moderate
0Minor
2,536No known interaction
293 Moderate 2,536 No interaction
Moderate

293 interactions

Showing 60 of 293 moderate interactions — see all 293 on the Indole-3-carbinol page.

No interaction 2,536 drugs checked — show the list

We also checked Indole-3-carbinol against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,536 medications checked with no known interaction — see the full Indole-3-carbinol list.

See the full Indole-3-carbinol interactions page
See every supplement checked against Segesterone Acetate, Ethinyl Estradiol, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Indole-3-carbinol monograph › Uses, safety, and every drug interaction in one place Segesterone Acetate, Ethinyl Estradiol supplement interactions › Every supplement checked against Segesterone Acetate, Ethinyl Estradiol, ranked by severity Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Indole-3-carbinol and Segesterone Acetate, Ethinyl Estradiol Together: Common Questions

Can you take Indole-3-carbinol with Segesterone Acetate, Ethinyl Estradiol?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Indole-3-carbinol and Segesterone Acetate, Ethinyl Estradiol?
Segesterone Acetate, Ethinyl Estradiol belongs to more than one drug category, and Indole-3-carbinol interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Indole-3-carbinol and Segesterone Acetate, Ethinyl Estradiol interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Segesterone Acetate, Ethinyl Estradiol and Indole-3-carbinol?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.