Drug & supplement interaction

Theanine + Benzocaine, Dextromethorphan

Benzocaine, Dextromethorphan brand name: Tetra-Formula.

Minor Interaction
Medically reviewed by · Updated February 2023
The bottom line Minor

Theanine has a minor interaction with Benzocaine, Dextromethorphan. Clinical studies regarding the effects of L-theanine on serotonin levels are conflicting.

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

Theanine and Benzocaine, Dextromethorphan

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

Minor

SEROTONERGIC DRUGS

Why this applies to Benzocaine, Dextromethorphan

Benzocaine, Dextromethorphan falls under SEROTONERGIC DRUGS — the group Theanine interacts with.

Clinical studies regarding the effects of L-theanine on serotonin levels are conflicting. Some studies suggest it can increase serotonin levels in the brain while others report that it may decrease them. Nevertheless, there have been no reports of l-theanine being a causative agent in serotonergic-related side effects or serotonin syndrome.
Severity Minor Likelihood Unlikely Evidence C

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

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

Here's the practical scoop on pairing L-theanine with a product like Tetra-Formula. The piece worth talking about is the dextromethorphan (the cough suppressant), since it nudges serotonin upward in the brain. L-theanine may also touch serotonin, but the research is genuinely mixed, with some studies showing a rise and others a dip. Honestly, there are no real-world reports of theanine triggering serotonin-related problems.

So this is a low-concern combination. In theory, if serotonin climbed too high you could see jitteriness, fast heartbeat, or feeling flushed, but that's very unlikely here. The benzocaine, a numbing agent, isn't part of this at all. Still, run it past your pharmacist, especially if you take other serotonin-affecting meds.

Contact Dr. Brian directly if you have additional questions on this interaction

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

Theanine Also Interacts With Other Medications

Theanine has 172 moderate, 392 minor known drug interactions in our database — the Benzocaine, Dextromethorphan one above is one of them. If you take anything else, check it against the full list below.

Moderate 172 Minor 392 No known interaction 2,266 (incl. Benzocaine, Dextromethorphan)
Taking anything else?

Check Another of Your Medications Against Theanine

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

From our Q&A

Questions About Theanine or Benzocaine, 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 Theanine or Benzocaine, 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 Benzocaine, Dextromethorphan

This page covers Theanine only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Benzocaine, Dextromethorphan page lists 24 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Lithium (major), 5-htp (moderate), Acetyl-l-carnitine (moderate), Ayahuasca (moderate) and Black Cohosh (moderate).

By severity: 1 major · 20 moderate · 3 minor.

From our pharmacist’s overview on the Benzocaine, Dextromethorphan page

“Tetra-Formula pairs benzocaine, a throat-numbing agent, with dextromethorphan, a cough suppressant that raises serotonin activity, and that second ingredient explains why 21 of the 24 supplement interactions on file share one theme, pushing serotonin higher and raising the risk of serotonin syndrome (agitation, racing heart, fever, con…”

Reviewed by 2 · Jul 18, 2026

Open the Benzocaine, Dextromethorphan interaction page

One more smart check

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

We hold 3,298 real supplement products containing Theanine, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Theanine. Your product may carry other ingredients that interact with Benzocaine, Dextromethorphan too, on top of Theanine — 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 Theanine and Benzocaine, 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 Theanine
Top 5%

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

29 days ago today
Medication Benzocaine, Dextromethorphan
Top 10%

#162 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 Theanine

What is Theanine?

Theanine
  • Anxiety and stress
  • Relaxation and calm
  • Sleep support
  • Focus and cognitive function

Theanine (usually L-theanine) is an amino acid found naturally in tea leaves that many people take to feel calmer and less stressed without strong drowsiness. Early research suggests it may help with relaxation and stress, but evidence for most uses is still limited. It appears generally well tolerated for short-term use, but check with your pharmacist or doctor before starting it.

Read the full Theanine monograph & all interactions
Keep checking

Other Drugs & Theanine

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

0Major
172Moderate
392Minor
2,265No known interaction
172 Moderate 392 Minor 2,265 No interaction
Moderate

172 interactions

Showing 60 of 172 moderate interactions — see all 172 on the Theanine page.

Minor

392 interactions

Showing 60 of 392 minor interactions — see all 392 on the Theanine page.

No interaction 2,265 drugs checked — show the list

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

Showing the 60 most looked-up of 2,265 medications checked with no known interaction — see the full Theanine list.

See the full Theanine interactions page
See every supplement checked against Benzocaine, 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
Theanine monograph › Uses, safety, and every drug interaction in one place Benzocaine, Dextromethorphan supplement interactions › Every supplement checked against Benzocaine, Dextromethorphan, 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 Theanine and Benzocaine, Dextromethorphan Together: Common Questions

Can you take Theanine with Benzocaine, Dextromethorphan?
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 Theanine and Benzocaine, Dextromethorphan 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 Benzocaine, Dextromethorphan and Theanine?

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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.