Drug & supplement interaction

Cabbage + Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine

Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine brand name: Conar-A.

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

Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine falls into 3 drug categories that Cabbage can interact with; the most serious is rated moderate. Theoretically, cabbage might decrease levels of drugs metabolized by CYP1A2.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions3
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Cabbage and Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine

These two interact in 3 distinct ways. Each one is explained separately below.

Why Are There 3 Interactions?

Cabbage interacts with whole categories of medication. Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine falls into 3 of those categories, so it can interact with Cabbage in 3 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES

1 of 3

Why this applies to Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine

Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine falls under CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES — the group Cabbage interacts with.

Theoretically, cabbage might decrease levels of drugs metabolized by CYP1A2.
Some animal research suggests that cabbage or its constituent indole-3-carbinol might increase drug metabolism and elimination by stimulating CYP1A2 activity.
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 gist with this combination cold and cough product (Conar-A). The thinking is that cabbage, especially in concentrated amounts, might gently rev up a liver enzyme called CYP1A2. If that enzyme speeds up, a drug it processes could get cleared a little faster, which can mean slightly less effect. Of the ingredients here, this mostly applies in a minor way to acetaminophen and dextromethorphan. None of these are prodrugs, so the practical worry would be a touch less fever, pain, or cough relief, not extra side effects.

Honestly, this is theoretical and only seen in lab and animal studies. Eating cabbage as food is very unlikely to matter. If you're using high-dose cabbage supplements, just run it by your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Balk JL. Indole-3-carbinol for cancer prevention. Altern Med Alert 2000; 3:105-7.
  2. He YH, Friesen MD, Ruch RJ, Schut HA. Indole-3-carbinol as a chemopreventive agent in 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) carcinogenesis: inhibition of PhIP-DNA adduct formation, acceleration of PhIP metabolism, and induction of cytoch
  3. Steinkellner, H., Rabot, S., Freywald, C., Nobis, E., Scharf, G., Chabicovsky, M., Knasmuller, S., and Kassie, F. Effects of cruciferous vegetables and their constituents on drug metabolizing enzymes involved in the bioactivation of DNA-reactive dietary c
Moderate

GLUCURONIDATED DRUGS

2 of 3

Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine also falls under GLUCURONIDATED DRUGS.

Theoretically, cabbage might increase clearance and decrease the effects of drugs metabolized through glucuronide conjugation.
A small clinical study shows that daily consumption of cabbage and Brussels sprout decreases levels of some drugs metabolized through glucuronide conjugation.
Severity Moderate Likelihood Probable Evidence B

Interaction 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..

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

This combination cold product (Conar-A) contains acetaminophen for pain and fever, plus dextromethorphan, guaifenesin, and phenylephrine. The piece that matters here is acetaminophen, which your body partly clears by attaching a sugar molecule to it (a process called glucuronidation). A small study suggested that eating cabbage and Brussels sprouts regularly can speed up that clearance, meaning a bit less of the drug may stick around.

In plain terms, large, daily amounts of cabbage could make the acetaminophen portion work slightly less well, so your fever or aches might not be covered quite as long. This is modest and somewhat theoretical, and normal helpings of cabbage at dinner are very unlikely to matter. If you eat a lot of it and feel your cold medicine isn't doing its job, check with your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Pantuck EJ, Pantuck CB, Anderson KE, et al. Effect of brussels sprouts and cabbage on drug conjugation. Clin Pharmacol Ther 1984;35:161-9. PubMed
Moderate

ACETAMINOPHEN (Tylenol, others)

3 of 3
Cabbage might increase clearance and reduce the effects of acetaminophen.
A small clinical study shows that daily consumption of cabbage and Brussels sprout decreases acetaminophen levels by as much as 16%, with some evidence suggesting that this effect is due to increased elimination through glucuronide conjugation.
Severity Moderate Likelihood Probable Evidence B

Interaction 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..

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

This combination product (Conar-A) includes acetaminophen for pain and fever, and that's the piece cabbage may touch. In a small study, eating cabbage and Brussels sprouts regularly nudged the body to clear acetaminophen a bit faster (by around 16%) through a process called glucuronide conjugation. In plain terms, cabbage could slightly speed up how quickly your body gets rid of the acetaminophen, which might make it work a touch less for fever or aches.

Here's the reassuring part: this is a modest effect, and normal food amounts of cabbage in your meals are unlikely to make a noticeable difference. The other ingredients (dextromethorphan, guaifenesin, phenylephrine) aren't part of this. If you eat a lot of cabbage or take cabbage supplements regularly, just mention it to your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Pantuck EJ, Pantuck CB, Anderson KE, et al. Effect of brussels sprouts and cabbage on drug conjugation. Clin Pharmacol Ther 1984;35:161-9. 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

Cabbage Also Interacts With Other Medications

Cabbage has 324 moderate known drug interactions in our database — the Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine one above is among them. If you take anything else, check it against the full list below.

Moderate 324 No known interaction 2,506 (incl. Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine)
Taking anything else?

Check Another of Your Medications Against Cabbage

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

Everything else you take

See Every Supplement That Interacts With Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine

This page covers Cabbage only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine page lists 261 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Asarabacca (major), Beer (major), Ephedra (major) and Grapefruit (major).

By severity: 12 major · 206 moderate · 43 minor.

From our pharmacist’s overview on the Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine page

“Picture the week someone takes Conar-A (acetaminophen, dextromethorphan, guaifenesin, phenylephrine): a miserable cold, coffee to push through, maybe wine at night or an herbal remedy on top. Those habits are exactly where this list turns serious.”

Reviewed by 2 · Jul 18, 2026

Open the Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine interaction page

One more smart check

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

We hold 2,304 real supplement products containing Cabbage, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Cabbage. Your product may carry other ingredients that interact with Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine too, on top of Cabbage — 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 Cabbage and Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine 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 Cabbage
Top 25%

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

29 days ago today
Medication Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine
Top 10%

#189 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 Cabbage

What is Cabbage?

Cabbage
  • Breast engorgement during breastfeeding
  • Joint pain and swelling (topical)
  • Digestive and stomach upset
  • General nutrition and antioxidant support
  • Skin and minor inflammation (topical)

Cabbage is a nutritious, low-calorie vegetable that is safe to eat as food and is sometimes applied to the skin as a leaf wrap for breast engorgement or sore joints. Most medicinal claims are based on tradition or limited research, with the strongest (though still modest) evidence being for cooling cabbage leaves on engorged breasts. Talk to your pharmacist or doctor before using cabbage in large amounts or as a treatment.

Read the full Cabbage monograph & all interactions
Keep checking

Other Drugs & Cabbage

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

0Major
324Moderate
0Minor
2,505No known interaction
324 Moderate 2,505 No interaction
Moderate

324 interactions

Showing 60 of 324 moderate interactions — see all 324 on the Cabbage page.

No interaction 2,505 drugs checked — show the list

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

Showing the 60 most looked-up of 2,505 medications checked with no known interaction — see the full Cabbage list.

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

Can you take Cabbage with Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine?
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 3 interactions listed for Cabbage and Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine?
Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine belongs to more than one drug category, and Cabbage 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 Cabbage and Acetaminophen, Dextromethorphan, Guaifenesin, Phenylephrine 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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