Drug & supplement interaction

Castor Bean + Alvimopan

Alvimopan brand name: Entereg.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Castor Bean and Alvimopan 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 two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Castor Bean and Alvimopan

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 Alvimopan and Castor Bean 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.

Castor Bean safety at a glance

Castor Bean overall Use caution Properly processed castor oil is generally safe in small amounts, but raw seeds are highly toxic.
Pregnancy Possibly Safe When castor oil is used orally in pregnant women at term. Although there have been reports of fetal meconium passage being more common with castor oil use in pr... Read the full pregnancy detail
Breastfeeding Use caution There is limited safety information, so avoid or use only under professional guidance.

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Alvimopan and Castor Bean? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Alvimopan

Interactions in our licensed database are recorded against drug classes, not just single drug names. Alvimopan is filed under 2 classifications — p-glycoprotein substrates, oral drugs. Castor Bean has documented interactions with 1 drug class — the most serious being diuretic drugs (moderate) — and none of Alvimopan’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

Castor Bean Does Interact With Other Medications

Castor Bean has 75 moderate known drug interactions in our database — Alvimopan isn’t one of them. If you take anything else, check it against the full list below.

Moderate 75 No known interaction 2,755 (incl. Alvimopan)
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.

What to actually watch for

No Interaction Found — But Data Suggests Castor Bean and Alvimopan May Share a Side Effect

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Stomach upset Additional detail

    Castor Bean

    “Orally, castor oil, like all stimulant laxatives, can cause abdominal discomfort, cramping, nausea, and faintness (15,272,40183,40186,40187,40192,40177,40185,40188,40163). Nausea can also occur because of the unpleasant taste of castor oil. Using flavored products might reduce this effect. Castor oil can also cause fluid and electrolyte loss, particularly potassium, which can result in hypokalemia.”

    Castor Bean · Natural Medicines adverse-effect record, reported in diarrhea.

    6 sources cited
    1. 15. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
    2. 272. Covington TR, et al. Handbook of Nonprescription Drugs. 11th ed. Washington, DC: American Pharmaceutical Association, 1996.
    3. 40183. Kris, M. G., Gralla, R. J., Clark, R. A., Tyson, L. B., and Groshen, S. Control of chemotherapy-induced diarrhea with the synthetic enkephalin BW942C: a randomized trial with placebo in patients receiving cisplatin. J Clin.Oncol. 1988;6(4):663-668. PubMed
    4. 40186. Ryan, J., Leighton, J., Kirksey, D., and McMahon, G. Evaluation of an enkephalin analog in men with castor oil-induced diarrhea. Clin.Pharmacol.Ther. 1986;39(1):40-42. PubMed
    5. 40187. Dodds, W. J., Scanlon, G. T., Shaw, D. K., Stewart, E. T., Youker, J. E., and Metter, G. E. An evaluation of colon cleansing regimens. AJR Am.J Roentgenol. 1977;128(1):57-59. PubMed
    6. 40192. Kolts, B. E., Lyles, W. E., Achem, S. R., Burton, L., Geller, A. J., and MacMath, T. A comparison of the effectiveness and patient tolerance of oral sodium phosphate, castor oil, and standard electrolyte lavage for colonoscopy or sigmoidoscopy preparatio

    Alvimopan

    Listed in the ADVERSE REACTIONS section of the FDA label for Alvimopan. Read the label on DailyMed ›

Reported for Castor Bean but not commonly for Alvimopan: bleeding in the gut, an electrolyte imbalance, shortness of breath and an allergic reaction.

Effects for Alvimopan come from the ADVERSE REACTIONS section of its FDA label; effects for Castor Bean come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 43 voluntary FDA FAERS reports for Alvimopan that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Castor Bean in Pregnancy & Breastfeeding

Pregnancy Possibly Safe

When castor oil is used orally in pregnant women at term. Although there have been reports of fetal meconium passage being more common with castor oil use in pregnant women, clinical research shows that the incidence of fetal meconium passage does not significantly differ from no castor oil use. Midwives routinely use castor oil for labor induction in pregnant women at term. This practice does not appear to adversely affect the mother or fetus. However, castor oil should not be used without the supervision of a clinician.

Pregnancy Likely Unsafe

When castor oil is used orally in pregnant women who are not at term. Castor oil might induce premature labor and induce miscarriage; avoid using.

Pregnancy Unsafe

When the whole seed is used orally. The chewed or uncoated seeds can cause severe toxic effects, including death; avoid using. There is insufficient reliable information available about the safety of using the hulled seed or topical use of castor during pregnancy.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

Overlapping uses

What Alvimopan Is Prescribed For, and What Castor Bean Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Alvimopan is a prescription medicine with approved uses on its FDA label. Castor Bean is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Alvimopan is prescribed for: Alvimopan capsules are used in hospitals to help the digestive tract recover more quickly after surgery that involves removing part of the bowel (partial bowel resection with primary anastomosis — meaning the remaining ends are reconnected). After this type of surgery, the bowel often temporarily stops working, a condition called postoperative ileus. This medication is only given during a short hospital stay and is not for long-term or home use.

Castor Bean has been studied for:

  • Constipation Natural Medicines rates the evidence for Castor Bean: Possibly Effective Read what the research shows

    Castor Bean for constipation

    Oral castor oil seems to improve symptoms of constipation.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Alvimopan on your own; if you are taking Castor Bean for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

Everything else you take

See Every Supplement That Interacts With Alvimopan

This page covers Castor Bean only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Alvimopan page lists 54 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), St. John's Wort (major), Bitter Melon (moderate), Black Pepper (moderate) and Bulbine Natalensis (moderate).

By severity: 2 major · 35 moderate · 17 minor.

From our pharmacist’s overview on the Alvimopan page

“Alvimopan (Entereg) is given for a few days after bowel surgery to help the gut start moving again, and its supplement list warrants genuine care, with two entries rated major. St.”

Reviewed by 2 · Jul 18, 2026

Open the Alvimopan interaction page

How much people look this up

Where Castor Bean and Alvimopan 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
Top half

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

29 days ago today
Medication Alvimopan
Top 25%

#345 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 Castor Bean reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Castor Bean and Alvimopan records this page draws on were last updated July 11, 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 .
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.

Ricinus communis · Euphorbiaceae · Seeds (beans) and the oil pressed from them · Castor oil (liquid), capsules, topical oils, and packs

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

Castor Bean: dosing

There is no single standard dose for all uses. For constipation, castor oil is sold as an over-the-counter laxative, and you should follow the directions on the product label or your pharmacist's advice. It is meant for short-term, occasional use only.Do not use higher amounts hoping for a stronger effect, and do not use it daily without medical guidance.

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

Read the full Castor Bean monograph & all interactions
Medication

About Alvimopan

What Is Alvimopan Used For?

Brand name: Entereg

Alvimopan capsules are used in hospitals to help the digestive tract recover more quickly after surgery that involves removing part of the bowel (partial bowel resection with primary anastomosis — meaning the remaining ends are reconnected). After this type of surgery, the bowel often temporarily stops working, a condition called postoperative ileus.

This medication is only given during a short hospital stay and is not for long-term or home use.

Most-Reported Side Effects for Alvimopan

From FAERS, the FDA’s public side-effect reporting system (43 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Hospitalisation 19 reports
Acute kidney injury 5 reports
Acute myocardial infarction 4 reports
Ileus 3 reports
Pruritus 3 reports
See full Alvimopan drug information
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
75Moderate
0Minor
2,754No known interaction
75 Moderate 2,754 No interaction
Moderate

75 interactions

Showing 60 of 75 moderate interactions — see all 75 on the Castor Bean page.

No interaction 2,754 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 2,754 medications checked with no known interaction — see the full Castor Bean list.

See the full Castor Bean interactions page
See every supplement checked against Alvimopan, ranked by severity
Evidence & sources

Castor Bean References

The 25 references that drive our Castor Bean 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.

  1. McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.
  2. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  3. Covington TR, et al. Handbook of Nonprescription Drugs. 11th ed. Washington, DC: American Pharmaceutical Association, 1996.
  4. McFarlin BL, Gibson MH, O'Rear J, Harman P. A national survey of herbal preparation use by nurse-midwives for labor stimulation. Review of the literature and recommendations for practice. J Nurse Midwifery 1999;44:205-16. PubMed
  5. Steingrub JS, Lopez T, Teres D, et al. Amniotic fluid embolism associated with castor oil ingestion. Crit Care Med 1988;16:642-3. PubMed
  6. Challoner KR, McCarron MM. Castor bean intoxication. Ann Emerg Med 1990;19:1177-83. PubMed
  7. Palatnick W, Tenenbein M. Hepatotoxicity from castor bean ingestion in a child. J Toxicol Clin Toxicol 2000;38:67-9. PubMed
  8. Isichei CO, Das SC, Ogunkeye OO, et al. Preliminary clinical investigation of the contraceptive efficacy and chemical pathological effects of RICOM-1013-J of Ricinus communis var minor on women volunteers. Phytother Res 2000;14:40-2.
  9. Garry D, Figueroa R, Guillaume J, Cucco V. Use of castor oil in pregnancies at term. Altern Ther Health Med 2000;6:77-9.
  10. Audi J, Belson M, Patel M, et al. Ricin poisoning: a comprehensive review. JAMA 2005;294:2342-51.
  11. Chen, C. C., Ng, W. W., Chang, F. Y., and Lee, S. D. Magnesium citrate-bisacodyl regimen proves better than castor oil for colonoscopic preparation. J.Gastroenterol.Hepatol. 1999;14(12):1219-1222. PubMed
  12. Azhari, S., Pirdadeh, S., Lotfalizadeh, M., and Shakeri, M. T. Evaluation of the effect of castor oil on initiating labor in term pregnancy. Saudi.Med J 2006;27(7):1011-1014. DOI
  13. Kris, M. G., Gralla, R. J., Clark, R. A., Tyson, L. B., and Groshen, S. Control of chemotherapy-induced diarrhea with the synthetic enkephalin BW942C: a randomized trial with placebo in patients receiving cisplatin. J Clin.Oncol. 1988;6(4):663-668. PubMed
  14. Mitri, F., Hofmeyr, G. J., and van Gelderen, C. J. Meconium during labour--self-medication and other associations. S.Afr.Med J 4-4-1987;71(7):431-433.
  15. Strates, B. S. and Hofmann, L. M. A randomized study of two preparations for large bowel radiology. Pharmatherapeutica 1987;5(1):57-61.

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 Castor Bean and Alvimopan Together: Common Questions

Is it safe to take Castor Bean with Alvimopan?
We do not list a known interaction between Castor Bean and Alvimopan. 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.
Do Castor Bean and Alvimopan have any of the same side effects?
Yes — our sources link each of them separately to one of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
Are Castor Bean and Alvimopan used for the same thing?
They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Castor Bean in each. That is a conversation for your prescriber, especially if Alvimopan is being adjusted to a target.
How was the Castor Bean and Alvimopan combination checked?
Interactions in our licensed database are recorded against drug classes. Alvimopan is filed under 2 classifications, and Castor Bean has documented interactions with 1 drug class — none of Alvimopan'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 Castor Bean interact with any other medications?
Yes. Castor Bean has 75 documented drug interactions in our database — Alvimopan 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 Alvimopan interact with any supplements?
Yes. Alvimopan has documented interactions with 54 supplements in our database — Castor Bean is not one of them. The Alvimopan 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

Castor Bean monograph Uses, safety profile, and every drug interaction in one place Alvimopan drug information The full plain-English guide to this medication Alvimopan supplement interactions Every supplement checked against Alvimopan, 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 25 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Alvimopan 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.