Drug & supplement interaction

Castor Bean + Hydrochlorothiazide, Methyldopa

Hydrochlorothiazide, Methyldopa brand names: Aldoril 15, Methazide, Aldoril 25, Aldoril D30.

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

Castor Bean has a moderate interaction with Hydrochlorothiazide, Methyldopa. Theoretically, castor oil might increase the risk of hypokalemia when taken with diuretic drugs.

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

Castor Bean and Hydrochlorothiazide, Methyldopa

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

Moderate

DIURETIC DRUGS

Why this applies to Hydrochlorothiazide, Methyldopa

Hydrochlorothiazide, Methyldopa falls under DIURETIC DRUGS — the group Castor Bean interacts with.

Theoretically, castor oil might increase the risk of hypokalemia when taken with diuretic drugs.
There is some concern that overuse of castor oil might compound diuretic-induced potassium 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. Your combo pill pairs hydrochlorothiazide (a water pill) with methyldopa (a blood pressure medicine). The water pill side already nudges your body to lose some potassium in the urine. Castor oil works as a strong stimulant laxative, and if you overuse it, the diarrhea can flush out extra potassium too. Stacked together, those two losses could leave your potassium running low.

Low potassium can show up as muscle cramps, weakness, fatigue, or an irregular heartbeat. This concern is mostly theoretical, based on how each works rather than strong studies, and an occasional normal dose of castor oil is unlikely to cause trouble. Still, regular or heavy use is where I'd be cautious. Please check with your pharmacist or doctor before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 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

Castor Bean Also Interacts With Other Medications

Castor Bean has 74 moderate known drug interactions in our database — the Hydrochlorothiazide, Methyldopa one above is one of them. If you take anything else, check it against the full list below.

Moderate 74 No known interaction 2,756 (incl. Hydrochlorothiazide, Methyldopa)
Taking anything else?

Check Another of Your Medications Against Castor Bean

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

Everything else you take

See Every Supplement That Interacts With Hydrochlorothiazide, Methyldopa

This page covers Castor Bean only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Hydrochlorothiazide, Methyldopa page lists 261 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), Asarabacca (major) and Beer (major).

By severity: 13 major · 223 moderate · 25 minor.

From our pharmacist’s overview on the Hydrochlorothiazide, Methyldopa page

“If you take hydrochlorothiazide with methyldopa (Aldoril, Methazide), this list deserves real attention, and the 13 major-rated entries are where to start. Most of the 261 ingredients either push blood pressure lower than intended or add to the diuretic effect, which can drain potassium.”

Reviewed by 2 · Jul 18, 2026

Open the Hydrochlorothiazide, Methyldopa interaction page

How much people look this up

Where Castor Bean and Hydrochlorothiazide, Methyldopa 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 Castor Bean
Steady interest

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

29 days ago today
Medication Hydrochlorothiazide, Methyldopa
Top 25%

#562 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 Castor Bean

What is Castor Bean?

  • Constipation relief
  • Skin and hair care
  • Labor induction (folk use)
  • Topical anti-inflammatory packs
  • Joint and muscle massage

Castor bean is the source of castor oil, a well-known stimulant laxative, but the raw seeds contain ricin, a potent and potentially deadly poison. The processed oil is generally considered safe when used as directed, while the whole or chewed seeds should never be eaten. Always talk to a pharmacist or doctor before using castor oil, especially during pregnancy or for children.

Read the full Castor Bean monograph & all interactions
Keep checking

Other Drugs & Castor Bean

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

0Major
74Moderate
0Minor
2,755No known interaction
74 Moderate 2,755 No interaction
Moderate

74 interactions

Showing 60 of 74 moderate interactions — see all 74 on the Castor Bean page.

No interaction 2,755 drugs checked — show the list

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

Showing the 60 most looked-up of 2,755 medications checked with no known interaction — see the full Castor Bean list.

See the full Castor Bean interactions page
See every supplement checked against Hydrochlorothiazide, Methyldopa, 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
Castor Bean monograph › Uses, safety, and every drug interaction in one place Hydrochlorothiazide, Methyldopa supplement interactions › Every supplement checked against Hydrochlorothiazide, Methyldopa, 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 Castor Bean and Hydrochlorothiazide, Methyldopa Together: Common Questions

Can you take Castor Bean with Hydrochlorothiazide, Methyldopa?
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 Castor Bean and Hydrochlorothiazide, Methyldopa 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 Hydrochlorothiazide, Methyldopa and Castor Bean?

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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.