Drug & supplement interaction

Black Cohosh + Acetaminophen, Codeine, Doxylamine

Acetaminophen, Codeine, Doxylamine brand name: Mersyndol.

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

Acetaminophen, Codeine, Doxylamine falls into 2 drug categories that Black Cohosh can interact with; the most serious is rated moderate. Some research suggests that black cohosh might inhibit CYP2D6, but there is conflicting evidence.

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

Black Cohosh and Acetaminophen, Codeine, Doxylamine

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

Why Are There 2 Interactions?

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

Moderate

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES

1 of 2

Why this applies to Acetaminophen, Codeine, Doxylamine

Acetaminophen, Codeine, Doxylamine falls under CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES — the group Black Cohosh interacts with.

Some research suggests that black cohosh might inhibit CYP2D6, but there is conflicting evidence.
Some clinical research suggests that black cohosh might modestly inhibit CYP2D6 and increase levels of drugs metabolized by this enzyme. However, contradictory clinical research shows a specific black cohosh product (Remifemin, Enzymatic Therapy) 40 mg twice daily does not significantly inhibit metabolism of a CYP2D6 substrate in healthy study volunteers. Until more is known, use black cohosh cautiously in patients taking drugs metabolized by CYP2D6.
Severity Moderate Likelihood Possible Evidence B

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 wrinkle with Mersyndol: the codeine in it is a prodrug. Your body has to switch codeine into morphine using a liver enzyme called CYP2D6, and that conversion is what gives you the pain relief. Black cohosh may modestly block (inhibit) that same enzyme, so in theory less codeine gets turned into morphine. That could mean weaker pain relief than you expected.

Honestly, the evidence here is shaky and conflicting, with one well-known product showing no real effect, so this may not amount to much for most people. The acetaminophen and doxylamine parts aren't a concern this way. Still, if your pain isn't well controlled, mention the black cohosh to your pharmacist or doctor before changing anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Gurley BJ, Gardner SF, Hubbard MA, et al. In vivo effects of goldenseal, kava kava, black cohosh, and valerian on human cytochrome P450 1A2, 2D6, 2E1, and 3A4/5 phenotypes. Clin Pharmacol Ther 2005;77:415-26. PubMed
  2. Gurley BJ, Swain A, Hubbard MA, et al. Clinical assessement of CYP2D6-mediated herb-drug interactions in humans: Effects of milk-thistle, black cohosh, goldenseal, kava kava, St. John's wort, and Echinacea. Mol Nutr Food Res 2008;52:755-63.
Moderate

HEPATOTOXIC DRUGS

2 of 2

Acetaminophen, Codeine, Doxylamine also falls under HEPATOTOXIC DRUGS.

Theoretically, taking black cohosh with hepatotoxic drugs may increase the risk of liver damage.
There is concern that black cohosh might be linked to cases of liver failure and autoimmune hepatitis.
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

The thing to watch with Mersyndol here is the acetaminophen part of the combo. Acetaminophen is processed by your liver, and in higher doses it's one of the more common causes of medication-related liver stress. Black cohosh, in rare cases, has been tied to liver problems of its own. So the worry is simply that combining two things that can each lean on the liver might add up.

I want to be honest about how soft this evidence is. This is theoretical and based mostly on scattered case reports, not strong studies. For most people taking Mersyndol as directed, it's unlikely to be a big deal. Still, watch for yellowing skin or eyes, dark urine, belly pain, or unusual tiredness, and run it past your pharmacist or doctor first, especially if you have any liver concerns.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Whiting PW, Clouston A, Kerlin P. Black cohosh and other herbal remedies associated with acute hepatitis. Med J Aust 2002;177:440-3. PubMed
  2. Lontos S, Jones RM, Angus PW, Gow PJ. Acute liver failure associated with the use of herbal preparations containing black cohosh. Med J Aust 2003;179:390-1.. DOI
  3. Cohen SM, O'Connor AM, Hart J, et al. Autoimmune hepatitis associated with the use of black cohosh: a case study. Menopause 2004;11:575-7. PubMed
  4. Vitetta L, Thomsen M, Sali A. Black cohosh and other herbal remedies associated with acute hepatitis. Med J Aust 2003;178:411-2.. PubMed
  5. Cohen B, Schardt D. Center for Science in the Public Interest. Letter to Food and Drug Administration. Commissioner Mark McClellan, MD, PhD. March 4, 2004.
  6. Levitsky J, Alli TA, Wisecarver J, Sorrell MF. Fulminant liver failure associated with the use of black cohosh. Dig Dis Sci 2005;50:538-9. PubMed
  7. MHRA. Black cohosh (Cimicifuga racemosa) - risk of liver problems. Herbal Safety News July 2006. Available at: http://www.mhra.gov.uk/home/idcplg?IdcService=SS_GET_PAGE&useSecondary= true&ssDocName=CON2024131&ssTargetNodeId=663.
  8. Lynch CR, Folkers ME, Hutson WR. Fulminant hepatic failure associated with the use of black cohosh: a case report. Liver Transpl 2006;12:989-92. PubMed
  9. Brar HS, Marathi R. Case of cholestatic drug-induced liver injury (DILI) associated with black cohosh. BMJ Case Rep 2021;14(5):e240408. 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

Black Cohosh Also Interacts With Other Medications

Black Cohosh has 635 moderate, 16 minor known drug interactions in our database — the Acetaminophen, Codeine, Doxylamine one above is among them. If you take anything else, check it against the full list below.

Moderate 635 Minor 16 No known interaction 2,179 (incl. Acetaminophen, Codeine, Doxylamine)
Taking anything else?

Check Another of Your Medications Against Black Cohosh

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

Everything else you take

See Every Supplement That Interacts With Acetaminophen, Codeine, Doxylamine

This page covers Black Cohosh only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Acetaminophen, Codeine, Doxylamine page lists 261 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), Asarabacca (major), Beer (major) and Gamma-hydroxybutyrate (ghb) (major).

By severity: 11 major · 208 moderate · 42 minor.

From our pharmacist’s overview on the Acetaminophen, Codeine, Doxylamine page

“Mersyndol pairs acetaminophen with codeine and doxylamine, two sedating drugs in one tablet, so I read its interaction list with genuine vigilance. Of the 261 supplements and herbs on file, the biggest hazard is anything else that slows the brain: 78 ingredients add sedation, and that group holds several of the 11 major-rated entries,…”

Reviewed by 2 · Jul 18, 2026

Open the Acetaminophen, Codeine, Doxylamine interaction page

One more smart check

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

We hold 1,472 real supplement products containing Black Cohosh, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Black Cohosh. Your product may carry other ingredients that interact with Acetaminophen, Codeine, Doxylamine too, on top of Black Cohosh — 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 Black Cohosh and Acetaminophen, Codeine, Doxylamine 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 Black Cohosh
Top 25%

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

29 days ago today
Medication Acetaminophen, Codeine, Doxylamine
Steady interest

#1,553 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 Black Cohosh

What is Black Cohosh?

Black Cohosh
  • Hot flashes and night sweats
  • Other menopause symptoms
  • Mood changes during menopause
  • Premenstrual syndrome (PMS)
  • Menstrual cramps

Black cohosh is a North American plant most often used to ease menopause symptoms like hot flashes, but the research is mixed and far from settled. It is generally well tolerated for short-term use, though rare reports of liver problems mean you should talk with your pharmacist or doctor before trying it, especially if you have liver disease.

Read the full Black Cohosh monograph & all interactions
Keep checking

Other Drugs & Black Cohosh

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

0Major
635Moderate
16Minor
2,178No known interaction
635 Moderate 16 Minor 2,178 No interaction
Moderate

635 interactions

Showing 60 of 635 moderate interactions — see all 635 on the Black Cohosh page.

Minor

16 interactions

No interaction 2,178 drugs checked — show the list

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

Showing the 60 most looked-up of 2,178 medications checked with no known interaction — see the full Black Cohosh list.

See the full Black Cohosh interactions page
See every supplement checked against Acetaminophen, Codeine, Doxylamine, 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
Black Cohosh monograph › Uses, safety, and every drug interaction in one place Acetaminophen, Codeine, Doxylamine supplement interactions › Every supplement checked against Acetaminophen, Codeine, Doxylamine, 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 Black Cohosh and Acetaminophen, Codeine, Doxylamine Together: Common Questions

Can you take Black Cohosh with Acetaminophen, Codeine, Doxylamine?
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 Black Cohosh and Acetaminophen, Codeine, Doxylamine?
Acetaminophen, Codeine, Doxylamine belongs to more than one drug category, and Black Cohosh 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 Black Cohosh and Acetaminophen, Codeine, Doxylamine 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.