Drug & supplement interaction

Colocynth + Metolazone

Metolazone brand names: Diulo, Zaroxolyn, Mykrox.

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

Colocynth has a moderate interaction with Metolazone. Theoretically, colocynth might increase the risk of hypokalemia when taken with potassium-depleting diuretic drugs.

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

Colocynth and Metolazone

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

Moderate

DIURETIC DRUGS

Why this applies to Metolazone

Metolazone falls under DIURETIC DRUGS — the group Colocynth interacts with.

Theoretically, colocynth might increase the risk of hypokalemia when taken with potassium-depleting diuretic drugs.
Colocynth is thought to have laxative effects, which might cause potassium depletion.
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 concern with these two together. Metolazone is a water pill that already pulls potassium out of your body through your urine. Colocynth is a harsh laxative, and the heavy, watery diarrhea it causes can flush out even more potassium. Stack those two effects and your potassium could drop too low, a state called hypokalemia.

Low potassium can leave you feeling weak, crampy, or tired, and in more serious cases it can throw off your heart's rhythm. I want to be honest though: this is a theoretical caution based on how these substances work, not on solid human studies. Honestly, the bigger issue is that colocynth itself is toxic and risky, so please check with your pharmacist or doctor before going anywhere near it.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.
  2. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.

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

Colocynth Also Interacts With Other Medications

Colocynth has 184 moderate known drug interactions in our database — the Metolazone one above is one of them. If you take anything else, check it against the full list below.

Moderate 184 No known interaction 2,646 (incl. Metolazone)
Taking anything else?

Check Another of Your Medications Against Colocynth

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

Everything else you take

See Every Supplement That Interacts With Metolazone

This page covers Colocynth only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Metolazone page lists 222 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), American Mistletoe (major), Dolomite (major) and Lithium (major).

By severity: 8 major · 190 moderate · 24 minor.

Open the Metolazone interaction page

One more smart check

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

We hold 2 real supplement products containing Colocynth, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Colocynth. Your product may carry other ingredients that interact with Metolazone too, on top of Colocynth — 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 Colocynth and Metolazone 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 Colocynth
Steady interest

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

29 days ago today
Medication Metolazone
Steady interest

#1,815 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 Colocynth

What is Colocynth?

  • Constipation
  • Digestive complaints
  • Diabetes (traditional use)
  • Joint and nerve pain
  • Skin conditions

Colocynth is a bitter desert gourd used in traditional medicine mainly as a powerful laxative, but it is highly toxic and can cause severe, sometimes deadly poisoning even at small doses. There is not enough good human evidence to support its use, and most pharmacists would advise against taking it. If you are curious about it, talk to a doctor or pharmacist before using any product that contains it.

Read the full Colocynth monograph & all interactions
Medication

About Metolazone

What Is Metolazone Used For?

Brand names: Diulo, Zaroxolyn, Mykrox

Metolazone tablets are used to treat edema (excess fluid buildup) linked to congestive heart failure or kidney diseases — including nephrotic syndrome and conditions with reduced kidney function. They are also used to treat high blood pressure (hypertension), either alone or alongside other blood pressure medications.

Metolazone tablets may also be used during pregnancy when edema is caused by a medical condition rather than normal pregnancy changes — but routine use in otherwise healthy pregnant women is not appropriate.

See full Metolazone drug information
Keep checking

Other Drugs & Colocynth

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

0Major
184Moderate
0Minor
2,645No known interaction
184 Moderate 2,645 No interaction
Moderate

184 interactions

Showing 60 of 184 moderate interactions — see all 184 on the Colocynth page.

No interaction 2,645 drugs checked — show the list

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

Showing the 60 most looked-up of 2,645 medications checked with no known interaction — see the full Colocynth list.

See the full Colocynth interactions page
See every supplement checked against Metolazone, 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
Colocynth monograph › Uses, safety, and every drug interaction in one place Metolazone supplement interactions › Every supplement checked against Metolazone, ranked by severity Metolazone 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 Colocynth and Metolazone Together: Common Questions

Can you take Colocynth with Metolazone?
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 Colocynth and Metolazone 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 Metolazone and Colocynth?

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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.