Drug & supplement interaction

Anise + Codeine Phosphate, Guaifenesin

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

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

Anise has a moderate interaction with Codeine Phosphate, Guaifenesin. Theoretically, anise oil might increase the effects and adverse effects of codeine.

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

Anise and Codeine Phosphate, Guaifenesin

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

Moderate

CODEINE

Theoretically, anise oil might increase the effects and adverse effects of codeine.
Animal research shows that anise oil increases the analgesic effects of codeine, possibly by inducing its phase I metabolism and increasing conversion to morphine. Whether this interaction occurs in humans is 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 thing about codeine: it's actually a prodrug, meaning your body has to convert it into morphine before it does much of anything for pain or coughing. The guaifenesin in this combo just loosens mucus and isn't really part of this interaction. The concern on file is that concentrated anise oil might speed up that conversion, leading to more morphine in your system. That could mean stronger effects but also more side effects like drowsiness, constipation, slowed breathing, or feeling overly sedated.

I want to be honest, though: this comes only from animal and lab studies, so we don't know if it happens in people. A little anise tea or seasoning almost certainly won't matter. If you're using concentrated anise oil regularly, just give your pharmacist or doctor a quick heads-up.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Samojlik I, Mijatovic V, Petkovic S, et al. The influence of essential oil of aniseed (Pimpinella anisum, L.) on drug effects on the central nervous system. Fitoterapia 2012;83:1466-73. 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

Anise Also Interacts With Other Medications

Anise has 192 moderate, 52 minor known drug interactions in our database — the Codeine Phosphate, Guaifenesin one above is one of them. If you take anything else, check it against the full list below.

Moderate 192 Minor 52 No known interaction 2,586 (incl. Codeine Phosphate, Guaifenesin)
Taking anything else?

Check Another of Your Medications Against Anise

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

Everything else you take

See Every Supplement That Interacts With Codeine Phosphate, Guaifenesin

This page covers Anise 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

One more smart check

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

We hold 465 real supplement products containing Anise, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Anise. Your product may carry other ingredients that interact with Codeine Phosphate, Guaifenesin too, on top of Anise — 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 Anise 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 Anise
Top half

#374 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 Anise

What is Anise?

Anise
  • Digestive upset and bloating
  • Cough and respiratory complaints
  • Sore throat
  • Menstrual discomfort
  • Flavoring agent

Anise is a fragrant, licorice-flavored seed used for centuries to ease digestion and soothe coughs. Most of its health claims are based on tradition and small or laboratory studies rather than strong human research, so evidence is limited. It is generally safe as a food and tea for most adults, but the concentrated essential oil should be used carefully and avoided in pregnancy.

Read the full Anise monograph & all interactions
Keep checking

Other Drugs & Anise

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

0Major
192Moderate
52Minor
2,585No known interaction
192 Moderate 52 Minor 2,585 No interaction
Moderate

192 interactions

Showing 60 of 192 moderate interactions — see all 192 on the Anise page.

Minor

52 interactions

No interaction 2,585 drugs checked — show the list

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

Showing the 60 most looked-up of 2,585 medications checked with no known interaction — see the full Anise list.

See the full Anise 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
Anise 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 Anise and Codeine Phosphate, Guaifenesin Together: Common Questions

Can you take Anise 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.
How serious is the Anise 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

Still Have a Question About Codeine Phosphate, Guaifenesin and Anise?

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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.