Drug Interaction Report

Theophylline and Estradiol: Interaction Details

A pharmacist-reviewed analysis of the Theophylline and Estradiol 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

Theophylline

Accurbron® Aerolate® Aquaphyllin® Asbron® Bronkodyl® Duraphyl® Elixicon® Elixomin®
+

Estradiol

Delestrogen
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 46 documented Theophylline interactions, 18 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

Increased theophylline exposure and theophylline toxicity (nausea, vomiting, palpitations, seizures)

Interaction Deep Dive

Combination oral/hormonal contraceptives containing some synthetic estrogens (ethinyl estradiol) may inhibit the metabolism of theophylline41 and may increase the plasma concentrations of theophylline 1. Combination contraceptives have been reported to decrease theophylline clearance by 34% and increase the half-life by 33% (7.9 vs 5.4 hr) 5. The distribution of theophylline has not been reported to change. A longer dosing interval may be possible while on combination contraceptives 2.

Why it happens (mechanism)

Inhibition of theophylline metabolism

Literature reports

1 report — tap to read

a) Low-dose oral contraceptives do not appear to influence single-dose (intravenous) theophylline pharmacokinetics in adolescents 3. No differences were found in theophylline distribution volume, elimination half-life, or total body clearance between control subjects (n=10) and subjects who received 3 to 9 months of low-dose oral contraceptives (n=10).

Common questions

Can I take Theophylline and Estradiol together?

Increased theophylline exposure and theophylline toxicity (nausea, vomiting, palpitations, seizures) Always confirm with your pharmacist or prescriber before making any change.

How serious is the Theophylline and Estradiol 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.

From our Q&A

Real reader questions about these medications, each personally answered by our pharmacist:

Questions for your pharmacist

  • Does my dose of Theophylline or Estradiol 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. 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
  2. Shenfield GM & Griffin JM: Clinical pharmacokinetics of contraceptive steroids: an update. Clin Pharmacokinet 1991; 20:15-37. PubMed
  3. Koren G, Chin TF, Correia J, et al: Theophylline pharmacokinetics in adolescent females following coadministration of oral contraceptives. Clin Invest Med 1985; 8:222-226.
  4. Product Information: Ortho Evra(TM), norelgestromin/ethinyl estradiol. Ortho-McNeil Pharmaceutical, Inc. Raritan, NJ, 2001.
  5. Tornatore KM, Kanarkoski R, McCarthy TL, et al: Effect of chronic oral contraceptive steroids on theophylline disposition. Eur J Clin Pharmacol 1982; 23:129. PubMed
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Theophylline

Keep reading about Theophylline

All Theophylline interactions (46) Theophylline drug information
Also serious with: Estradiol Transdermal Patch Medroxyprogesterone Capmatinib Levofloxacin Injection
Estradiol

Keep reading about Estradiol

All Estradiol interactions (216) Estradiol drug information
Also serious with: Ensitrelvir Tranexamic Acid Fezolinetant Penicillin V Potassium
Beyond drug–drug

These medications also interact with supplements

Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:

Theophylline + Activated Charcoal Ephedra Sida Cordifolia Adrafinil African Wild Potato Ashitaba Bacopa Baikal Skullcap + 118 more
Estradiol + Activated Charcoal Grapefruit St. John's Wort Acacia Rigidula Adrafinil African Wild Potato Aletris Alfalfa + 205 more

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This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.