Drug & supplement interaction

American Hellebore + Pacritinib

Pacritinib brand name: Vonjo.

Major Interaction
Medically reviewed by · Updated February 2024
The bottom line Major

American Hellebore has a major interaction with Pacritinib. American hellebore, also known as Veratrum viride, contains alkaloids that can potentially prolong the QT interval on an electrocardiogram (ECG).

Read the full interaction report
SeverityMajor
LikelihoodPossible
EvidenceC
What do Severity, Likelihood & Evidence mean?
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Interaction report

American Hellebore and Pacritinib

Here is the interaction we found between these two, with the evidence behind it.

Major

Qt Interval-Prolonging Drugs

Why this applies to Pacritinib

Pacritinib falls under Qt Interval-Prolonging Drugs — the group American Hellebore interacts with.

American hellebore, also known as Veratrum viride, contains alkaloids that can potentially prolong the QT interval on an electrocardiogram (ECG). This effect is similar to that of certain medications known as QT-prolonging drugs, which can increase the risk of a serious heart rhythm disorder called torsades de pointes (source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4728534/). Combining American hellebore with other drugs that cause QT-prolongation can increase the risk of adverse effects.
Severity Major Likelihood Possible Evidence C

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the heart of it: Pacritinib (Vonjo), which is used for certain types of myelofibrosis, can stretch out the QT interval, the timing of your heart's electrical reset. American Hellebore can do the same thing through its toxic alkaloids. Stack two QT-stretchers together and you raise the odds of a dangerous rhythm called torsades de pointes, which can cause fainting, a racing or fluttering heartbeat, or in rare cases something far more serious.

On top of that, this plant is genuinely poisonous and can crash your heart rate and blood pressure on its own. This isn't a safe pairing to experiment with. Please don't combine them, and check with your pharmacist or doctor before using anything containing this herb.

Contact Dr. Brian directly if you have additional questions on this interaction

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

American Hellebore Also Interacts With Other Medications

American Hellebore has 327 major, known drug interactions in our database — the Pacritinib one above is one of them. If you take anything else, check it against the full list below.

Major 327 No known interaction 2,503 (incl. Pacritinib)
Taking anything else?

Check Another of Your Medications Against American Hellebore

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

Everything else you take

See Every Supplement That Interacts With Pacritinib

This page covers American Hellebore only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Pacritinib page lists 158 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Arsenic (major), Cesium (major), Ephedra (major) and Grapefruit (major).

By severity: 8 major · 110 moderate · 40 minor.

From our pharmacist’s overview on the Pacritinib page

“Someone on pacritinib (Vonjo) is usually fighting myelofibrosis, and the supplements people reach for during cancer treatment, herbal blends, immune boosters, St. John's wort for mood, are where this list gets serious.”

Reviewed by 2 · Jul 18, 2026

Open the Pacritinib interaction page

How much people look this up

Where American Hellebore and Pacritinib 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 American Hellebore
Steady interest

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

29 days ago today
Medication Pacritinib
Steady interest

#1,676 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.

Supplement

About American Hellebore

What is American Hellebore?

American Hellebore
  • High blood pressure
  • Slowing heart rate
  • Toxemia of pregnancy (historical)
  • Convulsions (historical)
  • Pain relief (traditional)

American Hellebore (Veratrum viride) is a highly poisonous plant whose root contains toxic alkaloids that can cause dangerous drops in heart rate and blood pressure, even in small amounts. It is not a safe self-care supplement, and any non-homeopathic product carries a serious risk of poisoning. Do not use it without medical supervision, and talk to a pharmacist or doctor before considering any product that contains it.

Read the full American Hellebore monograph & all interactions
Medication

About Pacritinib

What Is Pacritinib Used For?

Brand name: Vonjo

Vonjo (pacritinib) is used to treat adults with intermediate or high-risk myelofibrosis (MF) — a serious bone marrow disease — including primary MF and secondary MF that developed after polycythemia vera or essential thrombocythemia (other blood disorders). It is specifically approved for patients whose platelet count is below 50 × 10⁹/L (very low platelets), a group that has limited treatment options.

This approval is based on demonstrated reductions in spleen size. Continued approval may depend on results from confirmatory trials showing broader clinical benefit.

See full Pacritinib drug information
Keep checking

Other Drugs & American Hellebore

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

327Major
0Moderate
0Minor
2,502No known interaction
327 Major 2,502 No interaction
Major

327 interactions

Showing 60 of 327 major interactions — see all 327 on the American Hellebore page.

No interaction 2,502 drugs checked — show the list

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

Showing the 60 most looked-up of 2,502 medications checked with no known interaction — see the full American Hellebore list.

See the full American Hellebore interactions page
See every supplement checked against Pacritinib, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
American Hellebore monograph › Uses, safety, and every drug interaction in one place Pacritinib supplement interactions › Every supplement checked against Pacritinib, ranked by severity Pacritinib drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking American Hellebore and Pacritinib Together: Common Questions

Can you take American Hellebore with Pacritinib?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the American Hellebore and Pacritinib interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or pharmacist.

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

Still Have a Question About Pacritinib and American Hellebore?

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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.