Drug & supplement interaction

Colocynth + Castor Oil (OTC drug)

Castor Oil (OTC drug) brand name: Purge.

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

Colocynth has a moderate interaction with Castor Oil (OTC drug). Theoretically, colocynth might increase the risk for fluid and electrolyte loss when taken with stimulant laxatives.

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

Colocynth and Castor Oil (OTC drug)

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

Moderate

STIMULANT LAXATIVES

Why this applies to Castor Oil (OTC drug)

Castor Oil (OTC drug) falls under STIMULANT LAXATIVES — the group Colocynth interacts with.

Theoretically, colocynth might increase the risk for fluid and electrolyte loss when taken with stimulant laxatives.
Colocynth is thought to have laxative effects. Concomitant use with stimulant laxatives might compound fluid and electrolyte loss.
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 simple version: both castor oil and colocynth work by stirring up your gut to force out watery stools. Castor oil isn't a prodrug in the tricky sense, but it does get broken down in your intestine into ricinoleic acid, which is the part that irritates the bowel and gets things moving. Colocynth does a very similar irritating job. Stack the two together and you're basically doubling down on the same effect.

The worry isn't that one cancels the other out. It's that combining them could push you into too much fluid and salt loss, meaning dehydration, cramping, dizziness, and low potassium. This is a theoretical concern based on how both work, not a proven danger, but honestly I'd steer clear of colocynth entirely since it can be toxic. Please check with your pharmacist or doctor first.

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 Castor Oil (OTC drug) 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. Castor Oil (OTC drug))
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 Castor Oil (OTC drug)

This page covers Colocynth only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Castor Oil (OTC drug) page lists 46 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Jalap (major), Oleander (major), Alder Buckthorn (moderate) and Aloe (moderate).

By severity: 3 major · 34 moderate · 9 minor.

From our pharmacist’s overview on the Castor Oil (OTC drug) page

“Castor oil, the classic over-the-counter purgative, deserves real care around supplements. Most of what's flagged against it are herbal laxatives in their own right, and doubling up can drain enough fluid and potassium to cause genuine harm, in some cases making plants that contain heart-active compounds, oleander chief among them, far…”

Reviewed by 2 · Jul 18, 2026

Open the Castor Oil (OTC drug) 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 Castor Oil (OTC drug) 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 Castor Oil (OTC drug) 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

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

29 days ago today
Medication Castor Oil (OTC drug)
Top 25%

#299 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
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 Castor Oil (OTC drug), 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 Castor Oil (OTC drug) supplement interactions › Every supplement checked against Castor Oil (OTC drug), 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 Colocynth and Castor Oil (OTC drug) Together: Common Questions

Can you take Colocynth with Castor Oil (OTC drug)?
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 Castor Oil (OTC drug) 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.