Drug & supplement interaction

Fever Bark + Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride

Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride brand name: Hycofenix.

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

Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride falls into 2 drug categories that Fever Bark can interact with; the most serious is rated moderate. Theoretically, fever bark might increase the levels and clinical effects of CYP2D6 substrates.

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

Fever Bark and Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride

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. Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride 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

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES

1 of 2

Why this applies to Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride

Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride falls under CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES — the group Fever Bark interacts with.

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 wrinkle with Hycofenix: the hydrocodone part is actually a prodrug. Your body uses an enzyme called CYP2D6 to turn some of it into hydromorphone, a stronger painkilling form. Fever bark contains a yohimbine-like compound that, in lab tests, slows CYP2D6 down. If that happens, less hydrocodone gets converted, so you might actually get less cough and pain relief from it.

I want to be honest though: this is only based on test-tube research, and how whole fever bark behaves in real people isn't known. So I wouldn't lose sleep over it. The bigger concern is that fever bark and the pseudoephedrine here can both nudge up blood pressure and heart rate. Please run this combo by your pharmacist or doctor before mixing them.

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
Moderate

STIMULANT DRUGS

2 of 2

Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride also falls under STIMULANT DRUGS.

Theoretically, fever bark might increase or decrease the effects of stimulant drugs.
Reserpine, a constituent of fever bark, might increase or decrease effects of sympathomimetics. Also, yohimbine, another constituent of fever bark, has sympathomimetic effects and increases blood pressure in a dose-dependent manner. It is not known if this would occur with fever bark.
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

The piece of your Hycofenix that matters here is the pseudoephedrine, the decongestant. It's a stimulant-type ingredient that can nudge up your blood pressure and heart rate. Fever bark contains plant alkaloids (reserpine-like and yohimbine-like compounds) that also tug on your blood pressure and nervous system, sometimes pushing it up and sometimes pulling it down. Combining the two could make those effects unpredictable.

In real life, that might show up as a racing or pounding heart, jitteriness, headache, or blood pressure swings. Honestly, the evidence here is thin and based mostly on anecdote, not solid studies. Still, fever bark is potent and poorly studied, so I'd steer clear and check with your pharmacist or doctor before mixing them.

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. McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.
  3. Sklar S, et al. Drug therapy screening system. Indianapolis, IN: First Data Bank 99.1-99. 2 eds.
  4. 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

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 Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride 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. Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride)
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 Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride

This page covers Fever Bark only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride page lists 241 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Beer (major), Ephedra (major) and Gamma-hydroxybutyrate (ghb) (major).

By severity: 13 major · 190 moderate · 38 minor.

From our pharmacist’s overview on the Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride page

“Hycofenix combines guaifenesin with hydrocodone, an opioid, and pseudoephedrine, a decongestant, so supplements can collide with it from two directions at once. That is why this list of 241 ingredients deserves real caution, starting with the 13 rated major.”

Reviewed by 2 · Jul 18, 2026

Open the Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride interaction page

How much people look this up

Where Fever Bark and Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride 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

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

29 days ago today
Medication Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride
Top 25%

#393 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
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 Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride, 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 Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride supplement interactions › Every supplement checked against Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride, 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 Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Fever Bark and Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride Together: Common Questions

Can you take Fever Bark with Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride?
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 Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride?
Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride 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 Guaifenesin, Hydrocodone Bitartrate, Pseudoephedrine Hydrochloride 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

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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.