Drug Interaction Report

Secobarbital and Estradiol Topical: Interaction Details

A pharmacist-reviewed analysis of the Secobarbital and Estradiol Topical interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Secobarbital

No brand names on record
+

Estradiol Topical

Divigel Divigel® Elestrin Elestrin® Estrasorb® Estrogel EstroGel® Evamist®
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
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Interaction severity
Major
Potentially serious — often needs a change or close monitoring.
How we grade severity & evidence

Severity levels

  • Contraindicated: These should generally not be used together.
  • Major: Potentially serious — often needs a change or close monitoring.
  • Moderate: Can be significant — usually manageable with monitoring.
  • Minor: Usually limited clinical impact.

Evidence grades

  • Established: Well documented — supported by controlled studies or strong clinical data.
  • Probable: Good supporting evidence, though not definitively proven.
  • Suspected: Some evidence suggests this interaction, but it is not well established.
  • Possible: Limited or conflicting evidence; the interaction may occur.
  • Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.

Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.

Of 40 documented Secobarbital interactions, 30 are rated major — including this one.
Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.
Onset
delayed
Evidence
theoretical
Severity
Major

What happens

Reduced hormonal contraceptive exposure, reduced efficacy of hormonal contraceptive and an increased risk of breakthrough bleeding/contraceptive failure

Interaction Deep Dive

Concomitant combination contraceptive and chronic barbiturate therapy may lead to an increased metabolism of contraceptive steroids, thus decreasing their effectiveness as a contraceptive124. This may result in unintended pregnancy or breakthrough bleeding 5. Concomitant use of COCs with a barbiturate, such as secobarbital, may reduce the plasma concentration of the estrogen and/or progestin component of the contraceptive and lead to decreased contraceptive efficacy or an increase in breakthrough bleeding. Advise patient to use an alternative method of contraception or a back-up method when coadministration is required and for 28 days after discontinuation of secobarbital 3.

Why it happens (mechanism)

Induction of CYP3A4-mediated metabolism of hormonal contraceptives

Common questions

Can I take Secobarbital and Estradiol Topical together?

Reduced hormonal contraceptive exposure, reduced efficacy of hormonal contraceptive and an increased risk of breakthrough bleeding/contraceptive failure Always confirm with your pharmacist or prescriber before making any change.

How serious is the Secobarbital and Estradiol Topical interaction?

It is rated major. Potentially serious — often needs a change or close monitoring.

How quickly could this interaction happen?

The documented onset is "delayed". Effects tend to build up gradually over days to weeks.

How strong is the evidence for this interaction?

The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.

Questions for your pharmacist

  • Does my dose of Secobarbital or Estradiol Topical need adjusting while I take them together?
  • What symptoms should prompt me to call you or my prescriber right away?
  • Does the timing of my doses matter for this combination?
  • Is there a safer alternative to one of these medications for me?

References (5)

  1. Mattson RH, Cramer JA, Darney PD, et al: Use of oral contraceptives by women with epilepsy. JAMA 1986; 256:238-240. DOI
  2. Haukkamaa M: Contraception by Norplant(R) subdermal capsules is not reliable in epileptic patients on anticonvulsant treatment. Contraception 1986; 33:559-565.
  3. Product Information: LOESTRIN(R) 24 Fe oral tablets, norethindrone acetate ethinyl estradiol oral tablets, ferrous fumarate oral tablets. Teva Pharmaceuticals USA Inc (per FDA), Parsippany, NJ, 2023. DailyMed
  4. Hempel E & Klinger W: Drug stimulated biotransformation of hormonal steroid contraceptives: clinical implications. Drugs 1976; 12:442-448. PubMed
  5. Product Information: Ortho Evra(TM), norelgestromin/ethinyl estradiol. Ortho-McNeil Pharmaceutical, Inc. Raritan, NJ, 2001.
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Secobarbital

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