Drug & supplement interaction

Fever Bark + Pazopanib

Pazopanib brand name: Votrient.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Pazopanib falls into 3 drug categories that Fever Bark can interact with; the most serious is rated moderate. Theoretically, CYP3A4 inhibitors might increase the levels and clinical effects of yohimbine, a constituent of fever bark.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions3
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Fever Bark and Pazopanib

These two interact in 3 distinct ways. Each one is explained separately below.

Why Are There 3 Interactions?

Fever Bark interacts with whole categories of medication. Pazopanib falls into 3 of those categories, so it can interact with Fever Bark in 3 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 3A4 (CYP3A4) INHIBITORS

1 of 3

Why this applies to Pazopanib

Pazopanib falls under CYTOCHROME P450 3A4 (CYP3A4) INHIBITORS — the group Fever Bark interacts with.

Theoretically, CYP3A4 inhibitors might increase the levels and clinical effects of yohimbine, a constituent of fever bark.
In vitro and clinical research shows that the fever bark constituent, yohimbine, is metabolized by CYP3A4 enzymes.
Severity Moderate Likelihood Possible Evidence D

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 gist of this one: pazopanib (Votrient) acts as a CYP3A4 blocker, and fever bark contains yohimbine, which your body normally clears using that same CYP3A4 pathway. So if you take them together, pazopanib could slow down how fast yohimbine is broken down, letting it build up. That matters because yohimbine can raise blood pressure and heart rate and make you feel jittery, anxious, or shaky. Pazopanib itself is already known to raise blood pressure, so stacking these effects isn't ideal.

That said, this is a theoretical concern based on how these chemicals behave, not real-world reports. Honestly, fever bark has little proven benefit and some risky alkaloids, so I'd skip it. Please check with your oncologist or pharmacist before combining anything new with pazopanib.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Le Corre P, Parmer RJ, Kailasam MT, et al. Human sympathetic activation by alpha2-adrenergic blockade with yohimbine: Bimodal, epistatic influence of cytochrome P450-mediated drug metabolism. Clin Pharmacol Ther. 2004;76(2):139-53.
  2. Bharucha AE, Skaar T, Andrews CN, et al Relationship of cytochrome P450 pharmacogenetics to the effects of yohimbine on gastrointestinal transit and catecholamines in healthy subjects. Neurogastroenterol Motil. 2008;20(8):891-9. PubMed
Moderate

CYTOCHROME P450 2D6 (CYP2D6) INHIBITORS

2 of 3

Pazopanib also falls under CYTOCHROME P450 2D6 (CYP2D6) INHIBITORS.

Theoretically, CYP2D6 inhibitors might increase the levels and clinical effects of yohimbine, a constituent of fever bark.
In vitro and clinical research shows that the fever bark constituent, yohimbine, is metabolized by CYP2D6 isoenzymes.
Severity Moderate Likelihood Possible Evidence D

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 wrinkle with this pairing: it's not really about your cancer medicine building up. Pazopanib (Votrient) can block a liver enzyme called CYP2D6, and that same enzyme is what your body uses to clear yohimbine, one of the active alkaloids in fever bark. So if Pazopanib slows that breakdown, the fever bark compounds could linger and hit harder than expected.

In plain terms, you'd see more of fever bark's effects, things like a racing heart, jittery feelings, and swings in blood pressure. This is a theoretical concern based on how the chemicals behave, not something proven in people. Still, fever bark is potent and poorly studied, so please check with your oncology team or pharmacist before combining the two.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Le Corre P, Parmer RJ, Kailasam MT, et al. Human sympathetic activation by alpha2-adrenergic blockade with yohimbine: Bimodal, epistatic influence of cytochrome P450-mediated drug metabolism. Clin Pharmacol Ther. 2004;76(2):139-53.
  2. Mueller-Schoell A, Michelet R, Weinelt F, Kloft C, Mikus G. CYP2D6 phenotype explains reported yohimbine concentrations in four severe acute intoxications. Arch Toxicol. 2021. PubMed
  3. Bharucha AE, Skaar T, Andrews CN, et al Relationship of cytochrome P450 pharmacogenetics to the effects of yohimbine on gastrointestinal transit and catecholamines in healthy subjects. Neurogastroenterol Motil. 2008;20(8):891-9. PubMed
Minor

ANTICOAGULANT/ANTIPLATELET DRUGS

3 of 3

Pazopanib also falls under ANTICOAGULANT/ANTIPLATELET DRUGS.

Theoretically, combining fever bark with antiplatelet or anticoagulant drugs might have additive effects; however, this has not been reported in clinical research.
Research in healthy adults shows that taking yohimbine, a constituent of fever bark, in doses of 8 mg or more, seems to inhibit platelet aggregation in vitro by binding to the alpha-2 adrenoceptor. The effects of fever bark itself are unclear.
Severity Minor Likelihood Possible Evidence D

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 gist for pazopanib (Votrient). Fever bark contains a yohimbine-like compound that, in lab studies, can make platelets a little less sticky, meaning blood may clot slightly less easily. Pazopanib already carries its own bleeding risk on the label, so the worry is that stacking the two could, in theory, add up and make bruising or bleeding (nosebleeds, bleeding gums, blood in urine or stool) more likely.

That said, this is a theoretical concern. It comes from test-tube work, not from real patients, and the effect of fever bark itself is unclear. Honestly, fever bark is one I'd steer clear of anyway because of its potent alkaloids. Since you're on cancer therapy, please run any supplement past your oncologist or pharmacist before starting it.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Mustonen, P., Savola, J., and Lassila, R. Atipamezole, an imidazoline-type alpha(2)-adrenoceptor inhibitor, binds to human platelets and inhibits their adrenaline-induced aggregation more effectively than yohimbine. Thromb.Res 8-1-2000;99(3):231-237.
  2. Berlin, I., Crespo-Laumonnier, B., Cournot, A., Landault, C., Aubin, F., Legrand, J. C., and Puech, A. J. The alpha 2-adrenergic receptor antagonist yohimbine inhibits epinephrine-induced platelet aggregation in healthy subjects. Clin Pharmacol.Ther. 199
  3. Braddock, L., Cowen, P. J., Elliott, J. M., Fraser, S., and Stump, K. Binding of yohimbine and imipramine to platelets in depressive illness. Psychol.Med 1986;16(4):765-773. PubMed
  4. Boon, N. A., Elliott, J. M., Grahame-Smith, D. G., John-Green, T., and Stump, K. A comparison of alpha 2-adrenoreceptor binding characteristics of intact human platelets identified by [3H]-yohimbine and [3H]- dihydroergocryptine. J Auton.Pharmacol 1983;3

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

Fever Bark Also Interacts With Other Medications

Fever Bark has 40 major, 673 moderate, 87 minor known drug interactions in our database — the Pazopanib one above is among them. If you take anything else, check it against the full list below.

Major 40 Moderate 673 Minor 87 No known interaction 2,030 (incl. Pazopanib)
Taking anything else?

Check Another of Your Medications Against Fever Bark

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

Everything else you take

See Every Supplement That Interacts With Pazopanib

This page covers Fever Bark only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Pazopanib page lists 349 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Arsenic (major), Asarabacca (major) and Beer (major).

By severity: 14 major · 297 moderate · 38 minor.

From our pharmacist’s overview on the Pazopanib page

“Take a careful look before mixing supplements with pazopanib (Votrient), an oral pill for advanced kidney cancer and certain sarcomas. Fourteen of the 349 ingredients on file are rated major, grapefruit among them, since it can raise pazopanib levels enough to intensify side effects.”

Reviewed by 2 · Jul 18, 2026

Open the Pazopanib interaction page

How much people look this up

Where Fever Bark and Pazopanib 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 Fever Bark
Steady interest

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

29 days ago today
Medication Pazopanib
Steady interest

#2,382 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 Fever Bark

What is Fever Bark?

Fever Bark
  • Fever
  • Diarrhea
  • Malaria (traditional)
  • Digestive complaints
  • Bitter tonic

Fever bark is the bark of the Australian tree Alstonia constricta, used in traditional medicine for fever, diarrhea, and infections. There is very little reliable human research to support these uses, and the bark contains potent alkaloids that may cause serious side effects. It is best avoided unless used under direct medical supervision.

Read the full Fever Bark monograph & all interactions
Medication

About Pazopanib

What Is Pazopanib Used For?

Brand name: Votrient

Pazopanib tablets — sold as the brand Votrient and as generic pazopanib — are used to treat two types of advanced cancer in adults: advanced renal cell carcinoma (RCC), the most common form of kidney cancer, and advanced soft tissue sarcoma (STS) in patients who have already received prior chemotherapy.

Important limitation: Pazopanib has not been shown to work in adipocytic soft tissue sarcoma (a subtype involving fat cells) or in gastrointestinal stromal tumors (GISTs), so it is not used for those cancers.

See full Pazopanib drug information
Keep checking

Other Drugs & Fever Bark

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

40Major
673Moderate
87Minor
2,029No known interaction
40 Major 673 Moderate 87 Minor 2,029 No interaction
Major

40 interactions

Moderate

673 interactions

Showing 60 of 673 moderate interactions — see all 673 on the Fever Bark page.

Minor

87 interactions

Showing 60 of 87 minor interactions — see all 87 on the Fever Bark page.

No interaction 2,029 drugs checked — show the list

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

Showing the 60 most looked-up of 2,029 medications checked with no known interaction — see the full Fever Bark list.

See the full Fever Bark interactions page
See every supplement checked against Pazopanib, 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
Fever Bark monograph › Uses, safety, and every drug interaction in one place Pazopanib supplement interactions › Every supplement checked against Pazopanib, ranked by severity Pazopanib 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 Fever Bark and Pazopanib Together: Common Questions

Can you take Fever Bark with Pazopanib?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 3 interactions listed for Fever Bark and Pazopanib?
Pazopanib belongs to more than one drug category, and Fever Bark interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Fever Bark and Pazopanib interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Pazopanib and Fever Bark?

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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.