Drug & supplement interaction

Watercress + Chlorzoxazone

Chlorzoxazone brand names: Parafon Forte DSC, Paraflex.

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

Watercress has a moderate interaction with Chlorzoxazone. Watercress might reduce the metabolism of chlorzoxazone and increase its effects and side effects.

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

Watercress and Chlorzoxazone

Here is the interaction we found between these two, with the evidence behind it.

Moderate

CHLORZOXAZONE (Parafon Forte, Paraflex)

Watercress might reduce the metabolism of chlorzoxazone and increase its effects and side effects. Clinical research in healthy volunteers shows that a single ingestion of watercress 50 grams increases the chlorzoxazone plasma concentration-time curve by about 56% and increases its half-life by about 53%.
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

Here's the gist for these two together. Your body relies on a liver enzyme (called CYP2E1) to break down chlorzoxazone, the muscle relaxer in Parafon Forte and Paraflex. Watercress appears to slow that enzyme down, so the drug clears more slowly and hangs around longer. In a small human study, even 50 grams of watercress raised chlorzoxazone blood levels by about 56% and stretched out how long it stayed in the body by roughly half.

In plain terms, you may feel more of the medicine than usual. That can mean extra drowsiness, dizziness, lightheadedness, or stomach upset. This isn't a reason to panic, but it's worth mentioning to your pharmacist or doctor, especially if you're eating watercress regularly or thinking about a concentrated extract. They can tell you if anything needs adjusting.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Leclercq I, Desager JP, Horsmans Y. Inhibition of chlorzoxazone metabolism, a clinical probe for CYP2E1, by a single ingestion of watercress. Clin Pharmacol Ther 1998;64:144-9. 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

Watercress Also Interacts With Other Medications

Watercress has 5 moderate known drug interactions in our database — the Chlorzoxazone one above is one of them. If you take anything else, check it against the full list below.

Moderate 5 No known interaction 2,825 (incl. Chlorzoxazone)
Taking anything else?

Check Another of Your Medications Against Watercress

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

From our Q&A

Questions About Watercress or Chlorzoxazone

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Watercress or Chlorzoxazone, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Chlorzoxazone

This page covers Watercress only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Chlorzoxazone page lists 26 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Procaine (major), Coffee Charcoal (moderate), Diosmin (moderate) and European Mandrake (moderate).

By severity: 2 major · 15 moderate · 9 minor.

From our pharmacist’s overview on the Chlorzoxazone page

“Chlorzoxazone (Parafon Forte DSC, Paraflex) is a muscle relaxant for painful spasms, and its supplement list is one I want readers genuinely careful with. Twenty-six ingredients are on file, two rated major, led by activated charcoal, which can soak up the drug in the gut and cut what your body actually receives.”

Reviewed by 2 · Jul 18, 2026

Open the Chlorzoxazone interaction page

One more smart check

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

We hold 820 real supplement products containing Watercress, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Watercress. Your product may carry other ingredients that interact with Chlorzoxazone too, on top of Watercress — 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 Watercress and Chlorzoxazone 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 Watercress
Top 25%

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

29 days ago today
Medication Chlorzoxazone
Top half

#1,286 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 Watercress

What is Watercress?

Watercress
  • Source of vitamins and minerals
  • Antioxidant support
  • General nutrition
  • Traditional cough and congestion remedy
  • Skin and detox tonics

Watercress is a nutrient-rich leafy green that provides vitamins A, C, and K plus minerals and antioxidant plant compounds. Eaten as a food it is generally safe and healthy for most people, but strong human evidence for concentrated supplement health claims is limited. Talk to your pharmacist or doctor before using high-dose extracts, especially if you are pregnant, breastfeeding, or have a medical condition.

Read the full Watercress monograph & all interactions
Medication

About Chlorzoxazone

What Is Chlorzoxazone Used For?

Brand names: Parafon Forte DSC, Paraflex

Chlorzoxazone tablets are used to relieve discomfort caused by acute, painful musculoskeletal conditions — things like muscle spasms and the pain that comes with them. It is meant to be used alongside rest, physical therapy, and other treatments, not as a stand-alone cure.

It is not intended for long-term muscle problems; it's most useful during a short-term flare of muscle pain and stiffness.

See full Chlorzoxazone drug information
Keep checking

Other Drugs & Watercress

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

0Major
5Moderate
0Minor
2,824No known interaction
5 Moderate 2,824 No interaction
Moderate

5 interactions

No interaction 2,824 drugs checked — show the list

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

Showing the 60 most looked-up of 2,824 medications checked with no known interaction — see the full Watercress list.

See the full Watercress interactions page
See every supplement checked against Chlorzoxazone, 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
Watercress monograph › Uses, safety, and every drug interaction in one place Chlorzoxazone supplement interactions › Every supplement checked against Chlorzoxazone, ranked by severity Chlorzoxazone drug information › The full plain-English guide to this medication 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 Watercress and Chlorzoxazone Together: Common Questions

Can you take Watercress with Chlorzoxazone?
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.
How serious is the Watercress and Chlorzoxazone 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 Chlorzoxazone and Watercress?

Our pharmacists answer your medication & supplement questions — free.

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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.