Drug & supplement interaction

Black Root + Promethazine

Promethazine brand name: Phenergan.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Black Root and Promethazine in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Black Root and Promethazine

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Promethazine and Black Root in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Black Root safety at a glance

Black Root overall Use caution Modern safety data are limited and the fresh root can cause significant digestive toxicity.
Pregnancy Possibly Unsafe When the fresh root is used orally. Anecdotally, fresh black root has been reported for have abortifacient and teratogenic effects. However, there is no reliabl... Read the full pregnancy detail
Breastfeeding Avoid Avoid while breastfeeding due to insufficient safety information.

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Promethazine and Black Root? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Promethazine

Interactions in our licensed database are recorded against drug classes, not just single drug names. Promethazine is filed under 4 classifications — including phenothiazines, anticholinergic drugs, photosensitizing drugs. Black Root has documented interactions with 3 drug classes — the most serious being digoxin (lanoxin) (moderate), diuretic drugs (moderate) and warfarin (coumadin) (moderate) — and none of Promethazine’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Black Root Does Interact With Other Medications

Black Root has 78 moderate known drug interactions in our database — Promethazine isn’t one of them. If you take anything else, check it against the full list below.

Moderate 78 No known interaction 2,752 (incl. Promethazine)
Taking anything else?

Check Another of Your Medications Against Black Root

Covers the 2,830 medications we’ve checked against Black Root. Pick one to open its full report.

What to actually watch for

No Interaction Found — But Data Suggests Black Root and Promethazine May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Drowsiness / Vomiting / Nausea reported in 11.7% of FDA reports for Promethazine Additional detail

    Black Root

    “Orally, black root can cause abdominal pain or cramps, changes in stool color or odor, drowsiness, headache, nausea, and vomiting. Hepatotoxicity has been reported after ingestion of large amounts.”

    Black Root · Natural Medicines adverse-effect record, reported in cluster headache.

    1 source cited
    1. 6002. Fetrow CW, Avila JR. Professional's Handbook of Complementary & Alternative Medicines. 1st ed. Springhouse, PA: Springhouse Corp., 1999.

    Promethazine

    Listed in the ADVERSE REACTIONS section of the FDA label for Promethazine, and in voluntary FDA adverse-event reports. Read the label on DailyMed ›

Reported for Black Root but not commonly for Promethazine: stomach pain, liver problems and headache.

Effects for Promethazine come from the ADVERSE REACTIONS section of its FDA label; effects for Black Root come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 22,361 voluntary FDA FAERS reports for Promethazine that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Black Root in Pregnancy & Breastfeeding

Pregnancy Possibly Unsafe

When the fresh root is used orally. Anecdotally, fresh black root has been reported for have abortifacient and teratogenic effects. However, there is no reliable scientific evidence about the effects of black root on pregnancy. Until more is known, black root should not be used during pregnancy.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

From our Q&A

Questions About Black Root or Promethazine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Black Root or Promethazine, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Promethazine

This page covers Black Root only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Promethazine page lists 83 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Henbane (major), Scopolia (major), Alfalfa (moderate) and Angel's Trumpet (moderate).

By severity: 3 major · 57 moderate · 23 minor.

From our pharmacist’s overview on the Promethazine page

“Promethazine (Phenergan) is a phenothiazine antihistamine used for allergies, nausea, and motion sickness, and it is strongly anticholinergic on its own, causing dry mouth, blurred vision, drowsiness, and constipation. That is why the 83 supplements and herbs on this list deserve real attention, starting with the three rated major.”

Reviewed by 2 · Jul 18, 2026

Open the Promethazine interaction page

One more smart check

Taking Black Root as Part of a Dietary Supplement Product? Check It for Interactions

We hold 41 real supplement products containing Black Root, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Black Root. Even though Black Root itself has no known interaction with Promethazine, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Black Root and Promethazine 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 Black Root
Top half

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

29 days ago today
Medication Promethazine
Steady interest

#2,128 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.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Black Root reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Black Root and Promethazine records this page draws on were last updated July 11, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Black Root

What is Black Root?

  • Constipation
  • Liver and gallbladder complaints
  • Digestive upset
  • Stimulating bile flow

Black Root is a traditional North American herb that was historically used as a strong laxative and to support digestion and liver function. There is very little modern scientific evidence to support these uses, and the fresh root can be toxic, so it should be used cautiously, if at all, and never during pregnancy or breastfeeding.

Veronicastrum virginicum · Plantaginaceae · Dried root and rhizome · Dried root, tincture, liquid extract, capsules, tea

An interaction check asks whether these two react with each other — it does not ask whether Black Root is a good idea for someone in your situation. Here is what our Black Root record says about it on its own.

Black Root: dosing

There is no established, standardized dose for Black Root, and modern dosing guidelines are lacking. Traditional preparations used the dried, aged root rather than the fresh root.Because of the risk of toxicity and strong laxative effects, you should not guess at a dose.

From our Black Root monograph — the full record covers uses, side effects and every documented interaction.

Read the full Black Root monograph & all interactions
Medication

About Promethazine

What Is Promethazine Used For?

Brand name: Phenergan

Promethazine is used for a wide range of conditions. Tablets, oral solution, and rectal suppositories (brands including Phenergan, Promethegan, and Phenadoz) are approved for seasonal and perennial allergic rhinitis, vasomotor rhinitis, allergic conjunctivitis, hives (urticaria), angioedema, dermographism, and allergic reactions to blood or plasma. They are also used for motion sickness (both prevention and active treatment), nausea and vomiting related to anesthesia and surgery, sedation, and as a helper medication alongside pain relievers after surgery.

Promethazine hydrochloride injection (brands including Phenergan and Promethazine HCl injection) is used for many of the same purposes but is reserved for situations where oral treatment is not possible — including allergic emergencies as an adjunct to epinephrine, sedation during labor, and as an aid during certain surgical procedures such as bronchoscopy and eye surgery.

Most-Reported Side Effects for Promethazine

From FAERS, the FDA’s public side-effect reporting system (22,614 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Dependence 3,586 reports
Nausea 2,646 reports
Vomiting 1,802 reports
Fatigue 1,496 reports
Diarrhea 1,341 reports
See full Promethazine drug information
Keep checking

Other Drugs & Black Root

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

0Major
78Moderate
0Minor
2,751No known interaction
78 Moderate 2,751 No interaction
Moderate

78 interactions

Showing 60 of 78 moderate interactions — see all 78 on the Black Root page.

No interaction 2,751 drugs checked — show the list

We also checked Black Root against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,751 medications checked with no known interaction — see the full Black Root list.

See the full Black Root interactions page
See every supplement checked against Promethazine, ranked by severity
Evidence & sources

Black Root References

The 2 references that drive our Black Root monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  2. Fetrow CW, Avila JR. Professional's Handbook of Complementary & Alternative Medicines. 1st ed. Springhouse, PA: Springhouse Corp., 1999.

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Black Root and Promethazine Together: Common Questions

Is it safe to take Black Root with Promethazine?
We do not list a known interaction between Black Root and Promethazine. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Black Root and Promethazine have any of the same side effects?
Yes — our sources link each of them separately to 3 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
How was the Black Root and Promethazine combination checked?
Interactions in our licensed database are recorded against drug classes. Promethazine is filed under 4 classifications, and Black Root has documented interactions with 3 drug classes — none of Promethazine's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Black Root interact with any other medications?
Yes. Black Root has 78 documented drug interactions in our database — Promethazine is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Promethazine interact with any supplements?
Yes. Promethazine has documented interactions with 83 supplements in our database — Black Root is not one of them. The Promethazine interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Black Root monograph Uses, safety profile, and every drug interaction in one place Promethazine drug information The full plain-English guide to this medication Promethazine supplement interactions Every supplement checked against Promethazine, 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 References The 2 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Promethazine and Black Root?

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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.