Drug & supplement interaction

Ceylon Leadwort + Acetaminophen, Codeine, Methocarbamol

Acetaminophen, Codeine, Methocarbamol brand names: Acetaminophen, Codeine, Methocarbamol, Robaxacet 8.

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

Acetaminophen, Codeine, Methocarbamol falls into 3 drug categories that Ceylon Leadwort can interact with; the most serious is rated moderate. Plumbagin, a constituent of Ceylon leadwort, has been shown to inhibit cytochrome P450 2D6 (CYP2D6) in vitro.

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

Ceylon Leadwort and Acetaminophen, Codeine, Methocarbamol

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

Why Are There 3 Interactions?

Ceylon Leadwort interacts with whole categories of medication. Acetaminophen, Codeine, Methocarbamol falls into 3 of those categories, so it can interact with Ceylon Leadwort 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 2D6 (CYP2D6) SUBSTRATES

1 of 3

Why this applies to Acetaminophen, Codeine, Methocarbamol

Acetaminophen, Codeine, Methocarbamol falls under CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES — the group Ceylon Leadwort interacts with.

Plumbagin, a constituent of Ceylon leadwort, has been shown to inhibit cytochrome P450 2D6 (CYP2D6) in vitro. So far, this interaction has not been reported in humans. Theoretically, Ceylon leadwort might increase the levels of drugs metabolized by CYP2D6. Some drugs metabolized by CYP2D6 include amitriptyline (Elavil), codeine, desipramine (Norpramin), flecainide (Tambocor), fluoxetine (Prozac), ondansetron (Zofran), tramadol (Ultram), and others.
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 wrinkle with this combination: the codeine part of your Robaxacet is a prodrug. Your body has to use an enzyme called CYP2D6 to turn codeine into morphine, which is what actually relieves pain. A compound in Ceylon Leadwort called plumbagin has been shown to slow that same enzyme down, at least in lab dishes.

So in theory, if this enzyme is blocked, less codeine gets converted to morphine, and you might get weaker pain relief rather than more. It's worth knowing this is based only on test-tube research, never confirmed in people, so I wouldn't lose sleep over it. The acetaminophen and methocarbamol pieces aren't really affected. Still, run it by your pharmacist before pairing them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Chen A, Zhou X, Tang S, Liu M, Wang X. Evaluation of the inhibition potential of plumbagin against cytochrome P450 using LC-MS/MS and cocktail approach. Sci Rep. 2016 Jun 22;6:28482. PubMed
Moderate

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES

2 of 3

Acetaminophen, Codeine, Methocarbamol also falls under CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES.

Plumbagin, a constituent of Ceylon leadwort, has been shown to inhibit cytochrome P450 1A2 (CYP1A2) in vitro. So far, this interaction has not been reported in humans. Theoretically, Ceylon leadwort might increase the levels of drugs metabolized by CYP1A2. Some substrates of CYP1A2 include clozapine (Clozaril), cyclobenzaprine (Flexeril), fluvoxamine (Luvox), haloperidol (Haldol), imipramine (Tofranil), mexiletine (Mexitil), olanzapine (Zyprexa), pentazocine (Talwin), propranolol (Inderal), tacrine (Cognex), zileuton (Zyflo), zolmitriptan (Zomig), and others.
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 to know about this combo pill (Robaxacet 8). Lab studies suggest plumbagin, a compound in Ceylon Leadwort, can slow down a liver enzyme called CYP1A2. Of the three ingredients here, methocarbamol (the muscle relaxer) is the one this enzyme helps clear. In theory, if that pathway gets blocked, methocarbamol could build up a bit and leave you feeling extra drowsy, dizzy, or foggy.

I want to be honest, though: this is only seen in test-tube research, not in real people, so the risk is uncertain and likely small. The codeine and acetaminophen parts aren't really tied to this enzyme. Still, since both Ceylon Leadwort and this medicine can make you sleepy, it's worth a quick chat with your pharmacist or doctor before pairing them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Chen A, Zhou X, Tang S, Liu M, Wang X. Evaluation of the inhibition potential of plumbagin against cytochrome P450 using LC-MS/MS and cocktail approach. Sci Rep. 2016 Jun 22;6:28482. PubMed
Moderate

CYTOCHROME P450 2E1 (CYP2E1) SUBSTRATES

3 of 3

Acetaminophen, Codeine, Methocarbamol also falls under CYTOCHROME P450 2E1 (CYP2E1) SUBSTRATES.

Plumbagin, a constituent of Ceylon leadwort, has been shown to inhibit cytochrome P450 2E1 (CYP2E1) in vitro. So far, this interaction has not been reported in humans. Theoretically, Ceylon leadwort might increase the levels of drugs metabolized by CYP2E1. Some drugs metabolized by CYP2E1 include acetaminophen, chlorzoxazone (Parafon Forte), ethanol, theophylline, and anesthetics such as enflurane (Ethrane), halothane (Fluothane), isoflurane (Forane), methoxyflurane (Penthrane).
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 piece that matters for this combo pill: the acetaminophen portion is partly handled by a liver enzyme called CYP2E1. A compound in Ceylon Leadwort (plumbagin) has been shown, in lab dishes only, to slow that enzyme down. In theory, if acetaminophen clears a little slower, more could hang around. The good news is that this would likely mean slightly higher acetaminophen levels, not a flood of the toxic byproduct that CYP2E1 normally makes.

So far this has not been seen in real people, only in test-tube studies, so I wouldn't lose sleep over it. The codeine and methocarbamol parts aren't really the concern here. Still, if you're tempted to use a concentrated Ceylon Leadwort supplement alongside this, run it by your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Chen A, Zhou X, Tang S, Liu M, Wang X. Evaluation of the inhibition potential of plumbagin against cytochrome P450 using LC-MS/MS and cocktail approach. Sci Rep. 2016 Jun 22;6:28482. 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

Ceylon Leadwort Also Interacts With Other Medications

Ceylon Leadwort has 1,096 moderate known drug interactions in our database — the Acetaminophen, Codeine, Methocarbamol one above is among them. If you take anything else, check it against the full list below.

Moderate 1,096 No known interaction 1,734 (incl. Acetaminophen, Codeine, Methocarbamol)
Taking anything else?

Check Another of Your Medications Against Ceylon Leadwort

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

Everything else you take

See Every Supplement That Interacts With Acetaminophen, Codeine, Methocarbamol

This page covers Ceylon Leadwort only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Acetaminophen, Codeine, Methocarbamol page lists 243 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: 10 major · 193 moderate · 40 minor.

Open the Acetaminophen, Codeine, Methocarbamol interaction page

One more smart check

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

We hold 96 real supplement products containing Ceylon Leadwort, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Ceylon Leadwort. Your product may carry other ingredients that interact with Acetaminophen, Codeine, Methocarbamol too, on top of Ceylon Leadwort — 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 Ceylon Leadwort and Acetaminophen, Codeine, Methocarbamol 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 Ceylon Leadwort
Top half

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

29 days ago today
Medication Acetaminophen, Codeine, Methocarbamol
Top 5%

#116 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 Ceylon Leadwort

What is Ceylon Leadwort?

  • Digestive complaints and poor appetite
  • Skin conditions and wounds (applied to the skin)
  • Joint pain and swelling
  • Traditional 'metabolism-boosting' tonics
  • Antimicrobial folk remedy

Ceylon Leadwort (Plumbago zeylanica) is a plant long used in Ayurvedic and other traditional medicine systems, mainly for digestion, skin problems, and pain. Solid human studies are lacking, and the plant contains plumbagin, a compound that can irritate skin and tissues and may be unsafe in larger amounts. Talk to a pharmacist or doctor before using it, and avoid it in pregnancy.

Read the full Ceylon Leadwort monograph & all interactions
Keep checking

Other Drugs & Ceylon Leadwort

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

0Major
1,096Moderate
0Minor
1,733No known interaction
1,096 Moderate 1,733 No interaction
Moderate

1,096 interactions

Showing 60 of 1,096 moderate interactions — see all 1,096 on the Ceylon Leadwort page.

No interaction 1,733 drugs checked — show the list

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

Showing the 60 most looked-up of 1,733 medications checked with no known interaction — see the full Ceylon Leadwort list.

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

Can you take Ceylon Leadwort with Acetaminophen, Codeine, Methocarbamol?
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 Ceylon Leadwort and Acetaminophen, Codeine, Methocarbamol?
Acetaminophen, Codeine, Methocarbamol belongs to more than one drug category, and Ceylon Leadwort 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 Ceylon Leadwort and Acetaminophen, Codeine, Methocarbamol 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 Acetaminophen, Codeine, Methocarbamol and Ceylon Leadwort?

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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.