Drug & supplement interaction

Masterwort + Castor Oil (OTC drug)

Castor Oil (OTC drug) brand name: Purge.

No Known Interaction

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Updated June 2026 · Pair last verified Oct 4, 2026

The bottom line No known interaction

We found no known interaction between Masterwort and Castor Oil (OTC drug) in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the label for Castor Oil (OTC drug) states a food rule worth keeping to.

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Interaction report

Masterwort and Castor Oil (OTC drug)

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Castor Oil (OTC drug) and Masterwort in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Masterwort safety at a glance

Masterwort overall Use caution Limited safety data exist, and the plant can cause sun-triggered skin reactions.

Pregnancy Avoid Not enough safety information; best avoided during pregnancy.

Breastfeeding Avoid No reliable safety data, so avoid while breastfeeding.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Castor Oil (OTC drug) and Masterwort? Ask Dr. Brian Staiger, PharmD, BCPS directly ›

How we checked

Why No Interaction Is Listed for Castor Oil (OTC drug)

Interactions in our licensed database are recorded against drug classes, not just single drug names. Castor Oil (OTC drug) is filed under 2 classifications — stimulant laxatives, oral drugs. Masterwort has documented interactions with 1 drug class — the most serious being photosensitizing drugs (moderate) — and none of Castor Oil (OTC drug)’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Masterwort Does Interact With Other Medications

Masterwort has 335 moderate known drug interactions in our database — Castor Oil (OTC drug) isn’t one of them. If you take anything else, check it against the full list below.

Moderate 335 No known interaction 2,495 (incl. Castor Oil (OTC drug))

Taking anything else?

Check Another of Your Medications Against Masterwort

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

How to take them

Some Castor Oil (OTC drug) Products Have a Food Rule — Masterwort Should Not Break It

At least one FDA label for a product containing Castor Oil (OTC drug) says to take it on an empty stomach. Most supplements — Masterwort included — are taken with a meal, so the easy mistake is swallowing both together at breakfast. Where that rule applies, keep Castor Oil (OTC drug) on its own and move Masterwort to a meal later in the day.

This may not be true of your version. Food instructions belong to the product, not the ingredient: two Castor Oil (OTC drug) products can carry different directions, and extended-release forms often differ from immediate-release ones. The label we read is quoted below — check the directions on your own box or bottle, or ask your pharmacist, for how to take the exact product you were given.

Directions Preferably taken on an empty stomach.

From the Dosage and Administration section of the FDA label we read for Castor Oil (OTC drug) — where that label names a specific product, the instruction is that product's.

A food rule is not an interaction — it is about how much of the medicine you absorb. The directions that came with your own product, and your pharmacist, outrank anything on this page.

Everything else you take

See Every Supplement That Interacts With Castor Oil (OTC drug)

This page covers Masterwort 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

How much people look this up

Where Masterwort 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 Masterwort

Top half

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

29 days ago today

Medication Castor Oil (OTC drug)

Top 25%

#304 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.

Where does our data come from?

Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Masterwort reference on this page ↓
Freshness: we automatically re-check this combination every week — this pair was last verified October 4, 2026. The Masterwort and Castor Oil (OTC drug) records this page draws on were last updated June 20, 2026.
What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.

Data structure & sourcing designed and verified by Dr. Brian Staiger, PharmD, BCPS.

Supplement

About Masterwort

What is Masterwort?

Digestive upset
Mild anxiety and tension
Skin complaints
Respiratory and cough relief
Traditional tonic

Masterwort (Heracleum sphondylium), a plant in the carrot family, has a long folk-medicine history for digestion, nerves, and skin. Modern scientific evidence to support these uses is very limited, and the plant can cause skin reactions to sunlight, so use it cautiously and talk with your pharmacist or doctor first.

Heracleum sphondylium · Apiaceae · Root, leaves, seeds, and aerial parts · Tea, tincture, dried herb, essential oil

An interaction check asks whether these two react with each other — it does not ask whether Masterwort is a good idea for someone in your situation. Here is what our Masterwort record says about it on its own.

Masterwort: dosing

There is no standardized, well-established dose for masterwort. Traditional preparations vary widely, and product strengths are not consistent.If you choose to use a commercial product, follow the directions on the label and do not exceed the suggested amount.

From our Masterwort monograph — the full record covers uses, side effects and every documented interaction.

Read the full Masterwort monograph & all interactions

Keep checking

Other Drugs & Masterwort

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

0Major

335Moderate

0Minor

2,494No known interaction

335 Moderate 2,494 No interaction

Moderate

335 interactions

Showing 60 of 335 moderate interactions — see all 335 on the Masterwort page.

No interaction 2,494 drugs checked — show the list

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

Showing the 60 most looked-up of 2,494 medications checked with no known interaction — see the full Masterwort list.

See the full Masterwort interactions page

See every supplement checked against Castor Oil (OTC drug), ranked by severity

Evidence & sources

Masterwort References

The 1 references that drive our Masterwort monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Masterwort and Castor Oil (OTC drug) Together: Common Questions

Is it safe to take Masterwort with Castor Oil (OTC drug)?

We do not list a known interaction between Masterwort and Castor Oil (OTC drug). That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.

Should I take Masterwort and Castor Oil (OTC drug) at the same time of day?

At least one FDA label for a product containing Castor Oil (OTC drug) says to take it on an empty stomach, and supplements are usually taken with a meal — so taking them together at breakfast is the easy mistake. Where that applies, keep Castor Oil (OTC drug) on its own and move Masterwort to a meal later in the day. Food instructions belong to the product rather than the ingredient, so check the directions on your own box. This is about absorption, not an interaction.

How was the Masterwort and Castor Oil (OTC drug) combination checked?

Interactions in our licensed database are recorded against drug classes. Castor Oil (OTC drug) is filed under 2 classifications, and Masterwort has documented interactions with 1 drug class — none of Castor Oil (OTC drug)'s classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.

Does Masterwort interact with any other medications?

Yes. Masterwort has 335 documented drug interactions in our database — Castor Oil (OTC drug) is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.

Does Castor Oil (OTC drug) interact with any supplements?

Yes. Castor Oil (OTC drug) has documented interactions with 46 supplements in our database — Masterwort is not one of them. The Castor Oil (OTC drug) interaction page linked on this page lists every one, ranked by severity.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Where next

Keep Exploring

Masterwort monograph Uses, safety profile, 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 References The 1 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Castor Oil (OTC drug) and Masterwort?

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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.