Drug & supplement interaction

Griffonia Simplicifolia + Dextromethorphan

Dextromethorphan brand names: Hold, Benylin Adult, Benylin Pediatric, Theraflu Thin Strips Long Acting Cough, Neo Citran Thin Strips Cough.

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

Griffonia Simplicifolia has a moderate interaction with Dextromethorphan. Theoretically, taking Griffonia simplicifolia seed extract with dextromethorphan might increase the risk of serotonergic adverse effects, such as serotonin syndrome and cerebral vasoconstrictive disorders such as Call-Fleming syndrome.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Griffonia Simplicifolia and Dextromethorphan

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

Moderate

DEXTROMETHORPHAN (Robitussin DM, others)

Theoretically, taking Griffonia simplicifolia seed extract with dextromethorphan might increase the risk of serotonergic adverse effects, such as serotonin syndrome and cerebral vasoconstrictive disorders such as Call-Fleming syndrome.
Griffonia simplicifolia seed extract contains 5-HTP. Taking 5-HTP with dextromethorphan increases the risk of serotonergic adverse effects.
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: Griffonia seeds are rich in 5-HTP, which your body turns into serotonin. Dextromethorphan, the cough suppressant in many over-the-counter products, also nudges serotonin levels in the brain. Stack the two and you could, in theory, push serotonin a little too high.

When serotonin runs too high, people can get what's called serotonin syndrome: things like agitation, a racing heart, sweating, shivering, muscle twitching, or feeling confused. To be honest, this warning is theoretical, based on how both work rather than reported cases, so the real-world risk is likely low, especially with a short course of cough medicine. Still, if you take this combo and feel any of those symptoms, stop and seek help. Better yet, check with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Singhal AB, Caviness VS, Begleiter AF, et al. Cerebral vasoconstriction and stroke after use of serotonergic drugs. Neurology 2002;58:130-3. PubMed
  2. Lemaire PA, Adosraku RK. An HPLC method for the direct assay of the serotonin precursor, 5-hydroxytrophan, in seeds of Griffonia simplicifolia. Phytochem Anal 2002;13(6):333-7.

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

Griffonia Simplicifolia Also Interacts With Other Medications

Griffonia Simplicifolia has 316 moderate known drug interactions in our database — the Dextromethorphan one above is one of them. If you take anything else, check it against the full list below.

Moderate 316 No known interaction 2,514 (incl. Dextromethorphan)
Taking anything else?

Check Another of Your Medications Against Griffonia Simplicifolia

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

From our Q&A

Questions About Griffonia Simplicifolia or Dextromethorphan

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

This page covers Griffonia Simplicifolia only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Dextromethorphan page lists 171 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), Lithium (major), St. John's Wort (major) and 1,3-dmaa (moderate).

By severity: 4 major · 125 moderate · 42 minor.

From our pharmacist’s overview on the Dextromethorphan page

“A glass of grapefruit juice can push dextromethorphan (Benylin, Hold, and other cough medicines) to higher levels than intended, one of four major-rated entries among the 171 supplements and herbs on file, and the list as a whole warrants real care. Most interactions trace back to the liver enzymes (CYP3A4 and CYP2D6) that clear dextro…”

Reviewed by 2 · Jul 18, 2026

Open the Dextromethorphan interaction page

One more smart check

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

We hold 3 real supplement products containing Griffonia Simplicifolia, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Griffonia Simplicifolia. Your product may carry other ingredients that interact with Dextromethorphan too, on top of Griffonia Simplicifolia — 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 Griffonia Simplicifolia and Dextromethorphan 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 Griffonia Simplicifolia
Steady interest

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

29 days ago today
Medication Dextromethorphan
Top 5%

#80 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 Griffonia Simplicifolia

What is Griffonia Simplicifolia?

Griffonia Simplicifolia
  • Low mood
  • Sleep problems
  • Anxiety
  • Appetite control
  • Headaches

Griffonia simplicifolia is a West African shrub whose seeds are a natural source of 5-HTP, a building block of the brain chemical serotonin. Some people use it for mood, sleep, and appetite, but high-quality human evidence is limited, and it should not replace prescribed treatment. Talk with your pharmacist or doctor before using it, especially if you take medicines that affect serotonin.

Read the full Griffonia Simplicifolia monograph & all interactions
Medication

About Dextromethorphan

What Is Dextromethorphan Used For?

Brand names: Hold, Benylin Adult, Benylin Pediatric, Theraflu Thin Strips Long Acting Cough, Neo Citran Thin Strips Cough

Dextromethorphan temporarily relieves cough due to minor throat and bronchial irritation, such as the kind that comes with the common cold or breathing in irritants. It also helps reduce the urge to cough so you — or your child — can get to sleep.

Some products, including CVS Long Acting Cough and Premier Value Tussin Cough oral liquids, are also indicated to help loosen phlegm (mucus) and thin bronchial secretions to help drain the airways.

See full Dextromethorphan drug information
Keep checking

Other Drugs & Griffonia Simplicifolia

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

0Major
316Moderate
0Minor
2,513No known interaction
316 Moderate 2,513 No interaction
Moderate

316 interactions

Showing 60 of 316 moderate interactions — see all 316 on the Griffonia Simplicifolia page.

No interaction 2,513 drugs checked — show the list

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

Showing the 60 most looked-up of 2,513 medications checked with no known interaction — see the full Griffonia Simplicifolia list.

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

Can you take Griffonia Simplicifolia with Dextromethorphan?
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.
How serious is the Griffonia Simplicifolia and Dextromethorphan 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 Dextromethorphan and Griffonia Simplicifolia?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

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.