Drug & supplement interaction

Bay Leaf + Codeine Phosphate, Guaifenesin

Codeine Phosphate, Guaifenesin brand names: Brontex, Robitussin AC.

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

Codeine Phosphate, Guaifenesin falls into 2 drug categories that Bay Leaf can interact with; the most serious is rated moderate. Theoretically, taking bay leaf in large amounts may enhance the therapeutic and adverse effects of sedatives.

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

Bay Leaf and Codeine Phosphate, Guaifenesin

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

Why Are There 2 Interactions?

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

Moderate

CNS DEPRESSANTS

1 of 2

Why this applies to Codeine Phosphate, Guaifenesin

Codeine Phosphate, Guaifenesin falls under CNS DEPRESSANTS — the group Bay Leaf interacts with.

Theoretically, taking bay leaf in large amounts may enhance the therapeutic and adverse effects of sedatives.
Bay leaf contains methyl eugenol. Animal research shows that methyl eugenol has sedative properties. Avoid concomitant use.
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 thing to keep in mind with your codeine and guaifenesin cough syrup: the codeine part is a sedating opioid, so it can already make you feel drowsy, foggy, or slow your breathing. Bay leaf contains a compound called methyl eugenol, and in animal studies that compound showed mild sedative effects. So the worry is that large, concentrated amounts of bay leaf could pile on top of codeine's drowsiness.

I want to be honest, this is a theoretical concern based on lab and animal work, not strong human proof. The pinch of bay leaf in a pot of soup is nothing to lose sleep over. It's really the concentrated supplements or essential oils I'd steer you away from while taking this. If you use those, please run it by your pharmacist or doctor first.

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.
Moderate

NARCOTIC DRUGS

2 of 2

Codeine Phosphate, Guaifenesin also falls under NARCOTIC DRUGS.

Theoretically, taking bay leaf in large amounts may enhance the therapeutic and adverse effects of narcotics. Avoid concomitant use.
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 situation with your cough syrup that pairs codeine with guaifenesin. The concern on file is theoretical, meaning it comes from how these ingredients behave in the body rather than from solid human studies. The idea is that large amounts of bay leaf (think concentrated supplements or essential oils, not the leaf you toss into a pot of soup) could add to the sedating, drowsy effects of the codeine portion.

If that happened, you might feel extra sleepy, lightheaded, or notice slower breathing and more constipation. Honestly, the cooking amount of bay leaf is very unlikely to cause any of this. Still, before you start a strong bay leaf supplement alongside this medicine, I'd run it past your pharmacist or doctor just to be safe.

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.

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

Bay Leaf Also Interacts With Other Medications

Bay Leaf has 334 moderate known drug interactions in our database — the Codeine Phosphate, Guaifenesin one above is among them. If you take anything else, check it against the full list below.

Moderate 334 No known interaction 2,496 (incl. Codeine Phosphate, Guaifenesin)
Taking anything else?

Check Another of Your Medications Against Bay Leaf

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

Everything else you take

See Every Supplement That Interacts With Codeine Phosphate, Guaifenesin

This page covers Bay Leaf only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Codeine Phosphate, Guaifenesin page lists 144 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), Gamma-hydroxybutyrate (ghb) (major) and Kava (major).

By severity: 7 major · 114 moderate · 23 minor.

Open the Codeine Phosphate, Guaifenesin interaction page

How much people look this up

Where Bay Leaf and Codeine Phosphate, Guaifenesin 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 Bay Leaf
Top 25%

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

29 days ago today
Medication Codeine Phosphate, Guaifenesin
Top 10%

#251 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 Bay Leaf

What is Bay Leaf?

Bay Leaf
  • Cooking and flavoring
  • Digestive upset
  • Blood sugar support
  • Colds and congestion
  • Joint and muscle discomfort

Bay leaf is a common culinary herb that is safe in the small amounts used in cooking. Some people take it for digestion, blood sugar, or colds, but strong human evidence for these uses is lacking. Talk to your pharmacist or doctor before using concentrated supplements or essential oils.

Read the full Bay Leaf monograph & all interactions
Keep checking

Other Drugs & Bay Leaf

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

0Major
334Moderate
0Minor
2,495No known interaction
334 Moderate 2,495 No interaction
Moderate

334 interactions

Showing 60 of 334 moderate interactions — see all 334 on the Bay Leaf page.

No interaction 2,495 drugs checked — show the list

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

Showing the 60 most looked-up of 2,495 medications checked with no known interaction — see the full Bay Leaf list.

See the full Bay Leaf interactions page
See every supplement checked against Codeine Phosphate, Guaifenesin, 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
Bay Leaf monograph › Uses, safety, and every drug interaction in one place Codeine Phosphate, Guaifenesin supplement interactions › Every supplement checked against Codeine Phosphate, Guaifenesin, 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 Bay Leaf and Codeine Phosphate, Guaifenesin Together: Common Questions

Can you take Bay Leaf with Codeine Phosphate, Guaifenesin?
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 Bay Leaf and Codeine Phosphate, Guaifenesin?
Codeine Phosphate, Guaifenesin belongs to more than one drug category, and Bay Leaf 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 Bay Leaf and Codeine Phosphate, Guaifenesin 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.