Drug & supplement interaction

Quassia + Famotidine

Famotidine brand names: Pepcid, Famotidine, Pepcid AC, Famotidine Injection.

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

Quassia has a minor interaction with Famotidine. Theoretically, due to reports that quassia increases stomach acid, quassia might decrease the effectiveness of H2-blockers.

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

Quassia and Famotidine

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

Minor

H2-BLOCKERS

Why this applies to Famotidine

Famotidine falls under H2-BLOCKERS — the group Quassia interacts with.

Theoretically, due to reports that quassia increases stomach acid, quassia might decrease the effectiveness of H2-blockers. The H2 blockers include cimetidine (Tagamet), ranitidine (Zantac), nizatidine (Axid), and famotidine (Pepcid).
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 simple version: famotidine (Pepcid) works by lowering the amount of acid your stomach makes, which eases heartburn and helps ulcers heal. Quassia is a strong bitter that may do the opposite by nudging your stomach to make a little more acid. So the worry is that quassia could partly work against famotidine, meaning your heartburn or reflux might not be controlled quite as well.

That said, this is a very mild, theoretical concern based only on scattered anecdotal reports, not solid studies. A bitter taste in a small culinary amount is unlikely to cause trouble. If you take concentrated quassia supplements regularly and notice your usual heartburn relief slipping, mention it to your pharmacist or doctor before changing anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.

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

Quassia Also Interacts With Other Medications

Quassia has 162 moderate, 35 minor known drug interactions in our database — the Famotidine one above is one of them. If you take anything else, check it against the full list below.

Moderate 162 Minor 35 No known interaction 2,633 (incl. Famotidine)
Taking anything else?

Check Another of Your Medications Against Quassia

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

From our Q&A

Questions About Quassia or Famotidine

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

This page covers Quassia only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Famotidine page lists 41 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), African Wild Potato (moderate), Banderol (moderate), Beer (moderate) and Biofeedback (moderate).

By severity: 1 major · 19 moderate · 21 minor.

From our pharmacist’s overview on the Famotidine page

“Famotidine (Pepcid) treats heartburn and acid reflux, a low-stakes job most days, but its interaction list earns genuine caution because one entry is rated major. That entry is activated charcoal, which can bind famotidine in the gut and sharply cut how much of the drug reaches your blood.”

Reviewed by 2 · Jul 18, 2026

Open the Famotidine interaction page

One more smart check

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

We hold 172 real supplement products containing Quassia, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Quassia. Your product may carry other ingredients that interact with Famotidine too, on top of Quassia — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Quassia and Famotidine 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 Quassia
Top half

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

29 days ago today
Medication Famotidine
Top 25%

#470 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 Quassia

What is Quassia?

  • Loss of appetite
  • Digestive upset
  • Head lice (topical)
  • Intestinal worms/parasites
  • Bitter tonic

Quassia is a tropical wood known for its very bitter taste, traditionally used as a digestive bitter and as a folk remedy for parasites and head lice. Human evidence for these uses is limited, and high doses may irritate the stomach, so it should be used cautiously and avoided in pregnancy.

Read the full Quassia monograph & all interactions
Medication

About Famotidine

What Is Famotidine Used For?

Brand names: Pepcid, Famotidine, Pepcid AC, Famotidine Injection

Famotidine treats a range of acid-related conditions. Over-the-counter tablets (such as Acid Controller, Acid Reducer, Acid Relief, Amazon Basic Care Acid Reducer, Basic Care Acid Reducer, and Calmicid AC) relieve and prevent heartburn associated with acid indigestion and sour stomach.

Prescription-strength famotidine tablets and oral suspension are used for active duodenal ulcers (ulcers in the small intestine), active gastric ulcers (stomach ulcers), GERD — including erosive esophagitis (inflammation that damages the esophagus), and pathological hypersecretory conditions such as Zollinger-Ellison syndrome (a rare disorder causing the stomach to produce too much acid). The oral suspension is also indicated in children as young as newborns for GERD, and in children one year and older for peptic ulcer disease. Famotidine injection is used in hospitalized patients who cannot take oral medication.

See full Famotidine drug information
Keep checking

Other Drugs & Quassia

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

0Major
162Moderate
35Minor
2,632No known interaction
162 Moderate 35 Minor 2,632 No interaction
Moderate

162 interactions

Showing 60 of 162 moderate interactions — see all 162 on the Quassia page.

Minor

35 interactions

No interaction 2,632 drugs checked — show the list

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

Showing the 60 most looked-up of 2,632 medications checked with no known interaction — see the full Quassia list.

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

Can you take Quassia with Famotidine?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Quassia and Famotidine interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

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

Still Have a Question About Famotidine and Quassia?

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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.