Drug & supplement interaction

Fever Bark + Bisoprolol

Bisoprolol brand name: Zebeta.

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

Bisoprolol falls into 2 drug categories that Fever Bark can interact with; the most serious is rated moderate. Theoretically, fever bark might alter the effects of antihypertensive drugs.

Read the full interaction report
SeverityModerate
LikelihoodProbable
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Fever Bark and Bisoprolol

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Fever Bark interacts with whole categories of medication. Bisoprolol falls into 2 of those categories, so it can interact with Fever Bark in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

ANTIHYPERTENSIVE DRUGS

1 of 2

Why this applies to Bisoprolol

Bisoprolol falls under ANTIHYPERTENSIVE DRUGS — the group Fever Bark interacts with.

Theoretically, fever bark might alter the effects of antihypertensive drugs.
Yohimbine, a constituent of fever bark, is an alpha-2 adrenoceptor antagonist and has been reported to increase blood pressure in clinical research. Conversely, reserpine can reduce both systolic and diastolic blood pressure. Theoretically, concomitant use of fever bark and antihypertensive drugs can interfere with blood pressure control.
Severity Moderate Likelihood Probable Evidence D

Interaction 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..

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

Here's the tricky thing about fever bark: it pulls in two opposite directions. It contains yohimbine, which can raise blood pressure, and reserpine-like compounds, which can lower it. Since you're taking bisoprolol to keep your blood pressure and heart rate in check, adding fever bark could throw off that control in either direction.

If the yohimbine side wins out, you might notice your pressure creeping up even though you haven't changed your dose. If the reserpine side dominates, you could feel lightheaded, unusually tired, or dizzy when standing. I'll be honest, this is a theoretical concern based on the plant's chemistry, not strong human studies. Still, fever bark has potent alkaloids and isn't well studied, so please check with your pharmacist or doctor before combining the two.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996.
  2. Kearney T, Tu N, Haller C. Adverse drug events associated with yohimbine-containing products: a retrospective review of the California Poison Control System reported cases. Ann Pharmacother 2010;44:1022-9. PubMed
  3. Lobay D. Rauwolfia in the Treatment of Hypertension. Integr Med (Encinitas). 2015 Jun;14(3):40-6.
  4. Sheldon MB, Kotte JH. Effect of Rauwolfia serpentina and reserpine on the blood pressure in essential hypertension; a long-term double-blind study. Circulation. 1957 Aug;16(2):200-6.
Moderate

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES

2 of 2

Bisoprolol also falls under CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES.

Theoretically, fever bark might increase the levels and clinical effects of CYP2D6 substrates.
In vitro research suggests that yohimbine, a constituent of fever bark, inhibits CYP2D6 enzyme activity. The effects of fever bark itself are unclear.
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 simple version. Fever bark contains plant compounds (one of them is yohimbine) that, in lab dish studies, appear to slow down a liver enzyme called CYP2D6. Bisoprolol is partly handled by that same enzyme, and it works as-is, it isn't a prodrug that needs activating. So if that enzyme gets blocked, your body may clear bisoprolol a bit slower, letting more of it build up.

That could mean a stronger beta-blocker effect than expected: heart rate dropping too low, lightheadedness, unusual tiredness, or blood pressure running lower than your target. I want to be honest though, this is only theoretical from test-tube work, and fever bark's real effect in people is unknown. I'd skip fever bark and check with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. VandenBrink, B. M., Foti, R. S., Rock, D. A., Wienkers, L. C., and Wahlstrom, J. L. Prediction of CYP2D6 drug interactions from in vitro data: evidence for substrate-dependent inhibition. Drug Metab Dispos. 2012;40(1):47-53. PubMed

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 Bisoprolol 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. Bisoprolol)
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.

From our Q&A

Questions About Fever Bark or Bisoprolol

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Fever Bark or Bisoprolol, 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 Bisoprolol

This page covers Fever Bark only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Bisoprolol page lists 183 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), American Mistletoe (major), Indian Snakeroot (major) and Tyramine (major).

By severity: 5 major · 151 moderate · 27 minor.

From our pharmacist’s overview on the Bisoprolol page

“Bisoprolol (Zebeta) slows your heart and lowers your blood pressure, so treat these 183 supplement interactions as a genuine concern rather than fine print, and learn the five rated major first. Most of the list, 119 ingredients in all, either adds to bisoprolol's pressure-lowering effect or works against it, so your numbers can drift…”

Reviewed by 2 · Jul 18, 2026

Open the Bisoprolol interaction page

How much people look this up

Where Fever Bark and Bisoprolol 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

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

29 days ago today
Medication Bisoprolol
Top 5%

#65 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 Bisoprolol

What Is Bisoprolol Used For?

Brand name: Zebeta

Bisoprolol fumarate tablets are used to manage high blood pressure (hypertension). Lowering blood pressure reduces the strain on the heart and blood vessels, helping prevent serious complications over time.

It can be used on its own or combined with other blood pressure-lowering medicines, such as thiazide diuretics. All supported products — including those labeled as Bisoprolol and Bisoprolol Fumarate — share this indication.

See full Bisoprolol 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 Bisoprolol, 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 Bisoprolol supplement interactions › Every supplement checked against Bisoprolol, ranked by severity Bisoprolol 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 Bisoprolol Together: Common Questions

Can you take Fever Bark with Bisoprolol?
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 2 interactions listed for Fever Bark and Bisoprolol?
Bisoprolol 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 Bisoprolol 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 Bisoprolol 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.