Drug Interaction Report

Thioridazine and Nifedipine: Interaction Details

Name: Thioridazine and Nifedipine Interaction
Creator: Dr. Brian Staiger, PharmD, BCPS

A pharmacist-reviewed analysis of the Thioridazine and Nifedipine 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

Thioridazine

No brand names on record

Nifedipine

Adalat® Adalat® CC Afeditab CR Afeditab® CR Nifedical® XL Nifeditab® CR Procardia Procardia®

Medically reviewed by

Dr. Brian Staiger, PharmD, BCPS

Updated Aug 8, 2026

Editorial policy · Data sources

Interaction severity

Major

Potentially serious — often needs a change or close monitoring.

Minor

Moderate

Major

Contraindicated

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 117 documented Thioridazine interactions, 49 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

unspecified

Evidence

probable

Severity

Major

What happens

Reduced NIFEdipine exposure

Interaction Deep Dive

Avoid coadministration of NIFEdipine (CYP3A4 substrate) and CYP3A4 inducers as it may significantly reduce NIFEdipine exposure. Consider alternate antihypertensive treatment²¹.

Why it happens (mechanism)

Induction of CYP3A4-mediated metabolism of NIFEdipine

Common questions

Can I take Thioridazine and Nifedipine together?

Reduced NIFEdipine exposure Always confirm with your pharmacist or prescriber before making any change.

How serious is the Thioridazine and Nifedipine interaction?

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

How quickly could this interaction happen?

The documented onset is "unspecified". The timing of this interaction is not well characterized.

How strong is the evidence for this interaction?

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

Questions for your pharmacist

Does my dose of Thioridazine or Nifedipine 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)

Product Information: NIFEDIPINE oral tablet, extended-release, nifedipine oral tablet, extended-release. Aurobindo Pharma Limited (per DailyMed), East Windsor, NJ, 2024. DailyMed
Product Information: PROCARDIA XL(R) oral extended-release tablets, nifedipine oral extended-release tablets. Pfizer Labs (per Dailymed), New York, NY, 2023. DailyMed

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Thioridazine

Keep reading about Thioridazine

All Thioridazine interactions (117)

Also serious with: Amisulpride Injection Dasatinib Ofloxacin Oxaliplatin Injection

Nifedipine

Keep reading about Nifedipine

All Nifedipine interactions (325) Nifedipine drug information

Also serious with: Rifabutin Primidone Rifapentine Rifampin

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:

Thioridazine + Activated Charcoal American Hellebore Arsenic Cesium Ephedra Grapefruit Henbane Indian Snakeroot + 160 more

Nifedipine + Activated Charcoal American Hellebore American Mistletoe Beer Coca Coleus Grapefruit Siberian Cocklebur + 265 more

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

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A message from HelloPharmacist

About our interaction database: depth, not breadth

HelloPharmacist doesn't license one of the big commercial interaction databases, so what you'll find here is not a complete list of every known drug interaction. Instead, each entry is researched, analyzed, and written up individually — documented from the published literature, reviewed by a pharmacist, and cited so you can check every source yourself.

If a combination isn't listed here, it means we haven't documented it yet — never that it's safe. For screening a full medication list, we recommend pairing this site with a comprehensive tool like the Drugs.com Interaction Checker and, most importantly, a review by your own pharmacist. For a deep, plain-English, fully sourced explanation of a specific documented interaction — that's exactly what we built this for.

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.