Drug Interaction Report

Estradiol Transdermal Patch and Tizanidine: Interaction Details

A pharmacist-reviewed analysis of the Estradiol Transdermal Patch and Tizanidine 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

Tizanidine

No brand names on record
+

Estradiol Transdermal Patch

Alora® Climara® Esclim® Estraderm® FemPatch® Menostar Menostar® Minivelle®
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 194 documented Estradiol Transdermal Patch interactions, 151 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
rapid
Evidence
probable
Severity
Major

What happens

Increased tiZANidine exposure and an increased risk of tiZANidine-related hypotension, bradycardia or increased drowsiness

Interaction Deep Dive

The concomitant use of tiZANidine and oral contraceptives is not recommended. In a retrospective analysis of population pharmacokinetic data, 50% lower clearance of tiZANidine was reported in women taking oral contraceptives than in women not on oral contraceptives following single and multiple 4 mg doses of tiZANidine. If coadministration is clinically necessary, reduce the dose or discontinue tiZANidine therapy if hypotension, bradycardia, or excessive drowsiness occurs1.

Why it happens (mechanism)

Inhibition of CYP1A2-mediated metabolism of tiZANidine

Literature reports

1 report — tap to read

a) One study reported higher serum levels of tiZANidine in women taking oral contraceptives than in men 2. In a retrospective analysis of population pharmacokinetic data, 50% lower clearance of tiZANidine was reported in women taking oral contraceptives than in women not on oral contraceptives. Patients were given single and multiple 4 mg doses of tiZANidine 1.

Common questions

Can I take Estradiol Transdermal Patch and Tizanidine together?

Increased tiZANidine exposure and an increased risk of tiZANidine-related hypotension, bradycardia or increased drowsiness Always confirm with your pharmacist or prescriber before making any change.

How serious is the Estradiol Transdermal Patch and Tizanidine interaction?

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

How quickly could this interaction happen?

The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.

How strong is the evidence for this interaction?

The evidence is graded "probable". Good supporting evidence, though not definitively proven.

From our Q&A

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

Questions for your pharmacist

  • Does my dose of Estradiol Transdermal Patch or Tizanidine 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 (2)

  1. Product Information: ZANAFLEX(R) oral capsules, oral tablets, tizanidine HCl oral capsules, oral tablets. Legacy Pharma Inc. (per FDA), Georgetown, Grand Cayman, 2024. DailyMed
  2. Hutchinson DR: Modified release tizanidine: a review. J Int Med Res 1989; 17:565-573. PubMed
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Tizanidine

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Estradiol Transdermal Patch

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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:

Tizanidine + Activated Charcoal American Hellebore Arsenic Beer Cesium Ephedra Grapefruit Procaine + 135 more

major · moderate · minor — check everything you take with our drug–supplement interaction checker.

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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.