Does IBgard® Interact With Any Drugs?

In our latest question and answer, the pharmacist discusses potential drug interactions with the over the counter supplement IBgard®.

Does IBgard® Interact With Any Drugs?
Nov 13, 2019

SharonS asked

Can I use IBgard, which contains peppermint oil, if I take bupropion and Buspar (buspirone)? Thanks!

At a glance

  • Lab and animal studies show that peppermint oil, the active ingredient in IBgard®, could potentially interact with several prescription drugs, notably cyclosporine and codeine.
  • However, no human studies have discovered clinically significant interactions and most organizations, including the National Center of Complementary and Integrative Health, report that peppermint oil is likely safe when used in usual amounts.
  • As with all supplements and over the counter products, be sure to let your doctor know of everything you are taking so you can be monitored appropriately.


Green Capsules On White Table Background


Hello and thank you for submitting your question to us!

While you mentioned two specific drugs in your inquiry, bupropion and Buspar (buspirone), I will broaden then topic to whether or not any drug is known to interact with the dietary supplement IBgard® since that will be pertinent to any of our readers who wish to take it.

I will focus only on the potential for IBgard® to cause drug interactions, and won't investigate its overall effectiveness for treating the symptoms of IBS (irritable bowel syndrome). That is a topic for another article.

So, the first thing we'll do here is to break down the ingredients in IBgard® and go from there.

IBgard® Ingredients

According to the manufacturer website, IBgard® contains only one active ingredient, peppermint oil (which contains 41.5 mg of l-menthol). From their site:

"Each capsule contains 90 mg ultra-purified peppermint oil (l-Menthol: 41.5 mg). Other ingredients: microcrystalline cellulose, gelatin, methacrylic acid copolymer, hypromellose, methlycellulose, triethyl citrate, polysorbate 80, FD&C Yellow #5 and FD&C Green #3."

When discussing over the counter supplements and their potential to interact with other drugs, things can quickly get tricky if they contain multiple active ingredients. However, since IBgard® contains only one active ingredient, it is relatively simple to look into.

As you can see from the ingredient list, IBgard® does contain a number of inactive ingredients, which by their very nature, shouldn't exhibit any sort of pharmaceutical effect. Unless you have a specific allergy or sensitivity to any of them, you can disregard them in the discussion of drug interactions.

Peppermint Oil


So, IBgard® contains peppermint oil. The use of peppermint oil to treat stomach related issues (like nausea, heartburn, stomach cramps, etc...) and IBS is nothing new.

In fact, peppermint oil has been fairly well studied for the treatment of IBS specifically. Multiple studies show that it acts as an antispasmodic (i.e. has relaxing effects on the gastrointestinal tract) and has anti-inflammatory properties.

One such study, published in BMC Complement Altern Med in 2019, concluded the following:

"In the most comprehensive meta-analysis to date, PO [peppermint oil] was shown to be a safe and effective therapy for pain and global symptoms in adults with IBS."

As mentioned earlier in this answer, I want to focus on drug interactions with IBgard® (and thus peppermint oil), so I will leave off the talk of effectiveness here.

I simply wanted to point out IBgard® doesn't contain any groundbreaking or unstudied ingredient, it's simply peppermint oil (although the manufacturer website does discuss the fact that IBgard® contains a novel system of drug delivery that is formulated to release the peppermint oil into the small intestine that you can read about here if you wish).

It is important to note that peppermint oil naturally contains menthol, so don't get confused by the fact that the label points out both 'peppermint oil' and 'l-menthol'.

Peppermint oil is a natural product, and thus, contains several compounds. It doesn't simply contain one isolated ingredient like most pharmaceutical drugs.

Peppermint oil extracts contain anywhere between 30% to 70% menthol (IBgard® is around 46% menthol). The other compounds in peppermint oil, which we don't have to go into detail about (e.g. terpenes, pulegone, flavonoids, phenolic acids, etc...) also likely play an important part of its overall effect.

Peppermint Oil Interactions

Now that I've discussed IBgard® and peppermint oil, let's get to the answer of the question of 'does IBgard® (i.e. peppermint oil) have any drug interactions'?

The answer is a decidedly ambiguous 'maybe'. There just are not a lot of studies out there that have thoroughly tested whether or not peppermint oil can affect the absorption, metabolism or actions of pharmaceutical drugs.

In fact, it is essential to state at the outset, before getting into everything I have written below, that there are no studies that have shown any significant drug interactions in humans. All the studies I cover below were either done in animals or in a lab setting.

Additionally, for what's it's worth, the National Center for Complementary and Integrative Health, part of the U.S Department of Health and Human Services, states that peppermint oil is thought to be safe in commonly used doses:

"Peppermint oil appears to be safe when taken orally (by mouth) in the doses commonly used. Excessive doses of peppermint oil can be toxic."

It doesn't report any known drug interactions.

However, after doing some research, I wanted to discuss several potential ones that I came across.


Interestingly enough, the manufacturer website for IBgard®, in their FAQ section, does touch on whether or not it has the potential to interact with drugs. Here is what it says:

"Patients should consult with a physician before taking IBgard® with or without other products. The group of terpenes that peppermint oil belongs to, may interact with certain medications such as cyclosporine, affecting how quickly the body can break them down."

The website doesn't reference where this information comes from, but after searching through some published literature, I did find the study this is likely referring to.

The study, published in the Journal of Pharmaceutical Sciences in 2002, noted that in rats, peppermint oil significantly slowed the metabolism of cyclosporine. In fact, concentrations of cyclosporine were three times higher when compared to rats that weren't given peppermint oil.

This interaction, it should be noted, has not been reported in humans and results obtained in animal studies aren't always transferable to what we can expect to happen in humans.

Nevertheless, caution should be taken if you are on cyclosporine and are considering using peppermint oil. At the very least, your doctor should be aware so you can be appropriately monitored.

Other Interactions

Something that I would hope to spur additional testing of peppermint oil in humans were the results of an in vitro study (that is, a study completed in a lab setting and not in a living organism) that showed the peppermint oil may inhibit numerous metabolizing enzymes in the body, including:

  • CYP1A2
  • CYP2C8
  • CYP2C9
  • CYP2C19
  • CYP2D6
  • CYP3A4 (to a minor degree)

The study stated the following:

"Surprisingly, peppermint oil moderately inhibited all CYP enzymes except 3A4 which was inhibited by only 20% at a concentration of 500 mg/mL."

These results are important because CYP enzymes are the predominant means of drug metabolism in our bodies. In fact, more than 90% of drugs are metabolized via these enzymes.

Inhibition of these CYP enzymes could potentially increase concentrations of a given drug, like what I discussed above regarding cyclosporine (drug concentrations in that study tripled when given with peppermint oil).

Conversely, there are some drugs that require CYP metabolism to be transformed into their active form. One such drug is codeine, which is metabolized in the body to morphine, a potent opioid analgesic.

One study noted that the consistent use of peppermint oil decreased the effect of codeine in mice, likely because it wasn't being metabolized as well into morphine:

"Chronic PO [peppermint oil] intake (in both doses) led to a significant decrease of analgesic effect of codeine."

It is important to remember that even though the study I referenced above showed that peppermint oil may have an effect on many different metabolizing enzymes, it was only in a lab setting and was not using doses you would expect humans to take. Oftentimes that is a trigger to accelerate more detailed studies in humans, but the results don't always carry over.

Buspar & Bupropion

I quickly wanted to touch on the two drugs in your question, Buspar (buspirone) and bupropion.

Buspar is metabolized primarily by CYP3A4 while bupropion is metabolized by CYP2B6.

It is unlikely that peppermint oil will affect these drugs. Although there are no studies in humans, peppermint oil hasn't been shown to significantly affect either CYP3A4 or CYP2B6 unless used in doses far exceeding what is normally used.

Nevertheless, since there does appear to be a chance that peppermint could affect CYP3A4, and therefore subsequently affect Buspar, caution using both is advised and you should let your doctor know you are taking it.

Final Words

Now, where does all of this information leave us? Unfortunately, in a somewhat challenging position.

There certainly is evidence that peppermint oil could interact with a number of drugs, but, initial studies have mostly only shown effects in a lab setting or in animals.

Peppermint oil drug interaction studies in humans are essentially non-existent. The only studies I found were completed in animals (mice, rats) or in a lab setting.

Significant drug interactions have not been seen in humans and by most indications, it appears to be relatively safe to use with most medication.

Like any over the counter supplement or medication however, it is important to disclose everything you are taking to your doctor so they can advise and monitor your health appropriately.

Lastly, I did want to mention that our website (PharmacistAnswers) has a drug interaction checker you can use. However, it should be noted that it finds results based on potential metabolizing enzyme interactions from data supplied by DrugBank. That is why there are over 16 pages of potential interactions as it concerns peppermint oil! They are simply there to help you make an informed decision.

  1. IBgard® Manufacturer Website.
  2. Peppermint oil enhances cyclosporine oral bioavailability in rats: comparison with D-alpha-tocopheryl poly(ethylene glycol 1000) succinate (TPGS) and ketoconazole. PubMed
  3. Simultaneous determination of the inhibitory potency of herbal extracts on the activity of six major cytochrome P450 enzymes using liquid chromatography/mass spectrometry and automated online extraction. PubMed
  4. Final report on the safety assessment of Mentha Piperita (Peppermint) Oil, Mentha Piperita (Peppermint) Leaf Extract, Mentha Piperita (Peppermint) Leaf, and Mentha Piperita (Peppermint) Leaf Water. PubMed
  5. The impact of peppermint oil on the irritable bowel syndrome: a meta-analysis of the pooled clinical data. PubMed
  6. Peppermint Oil. NIH
  7. Acute and chronic pretreatment with essential oil of peppermint (Mentha × piperita L., Lamiaceae) influences drug effects. PubMed
  8. Peppermint Oil. PubChem
  9. Buspar Prescribing Information. FDA
  10. Wellbutrin Prescribing Information. GSK

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