Peppermint - Robitussin AC (Codeine Phosphate, Guaifenesin) Interaction
Herbal: Peppermint
Also Known As: Mentha x piperita, Black Peppermint, Brandy Mint, Extract of Peppermint, Field Mint, Herba Menthae, Huile de Menthe Poivrée, Lamb Mint, M. Balsamea Willd Extract, Menta Pepperita, Menta Piperita, Mentha Balsamea, Mentha Oil, Mentha Piperita Extract, Mentha Piperita Oil
Drug: Codeine Phosphate, Guaifenesin
Brand names:
Brontex, Robitussin AC

Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
May 04, 2025
Interaction Details
There were no interactions found between Codeine Phosphate, Guaifenesin and Peppermint. This does not mean the potential for an interaction does not exist, however. There is often a lack of studies and data surrounding traditional medicine, especially concerning drug interactions, so it is important to always consult your provider before making any changes to your medication regimen.
Pharmacist Analysis
Peppermint and peppermint oil have a number of theoretical interactions due to several lab and animal studies suggesting it can inhibit a variety of CYP metabolizing enzymes in the liver, including:
- CYP2C9
- CYP3A4
- CYP2C19
- CYP1A2
However, many of these interactions have not been seen in humans, and the likelihood of them being clinically significant is low. They are nevertheless important to be aware of.
There is no known interaction between peppermint and the drug in question here. They are considered safe to combine.
- Dr. Brian Staiger, PharmDPeppermint Overview

Peppermint - More Interactions
Peppermint interacts with 774 drugs
Interaction Rating Key
These severity listings are for informational use only. Never start, stop or otherwise change your therapy before speaking with your provider.
Major | The combined use of these agents is strongly discouraged as serious side effects or other negative outcomes could occur. |
Moderate | Use cautiously under the care of a healthcare professional or avoid this combination. A significant interaction or negative outcome could occur. |
Minor | Be aware that there is a chance of an interaction. Watch for warning signs of a potential interaction. |
Unknown | No interactions have been reported or no interaction data is currently available. |
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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.
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Drug descriptions are provided by MedlinePlus.