Drug & supplement interaction

Castor Bean + Famciclovir

Famciclovir brand name: Famvir.

No Known Interaction
The bottom line No known interaction

We found no known interaction between Castor Bean and Famciclovir 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 Famciclovir

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 Famciclovir 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 Famciclovir and Castor Bean? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Famciclovir

Interactions in our licensed database are recorded against drug classes, not just single drug names. Famciclovir is filed under a single classification — oral drugs. Castor Bean has documented interactions with 1 drug class — the most serious being diuretic drugs (moderate) — and none of Famciclovir’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 — Famciclovir isn’t one of them. If you take anything else, check it against the full list below.

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 Famciclovir May Share Several of the Same Side Effects

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. 3 of them are worth acting on rather than waiting out — marked below.

  • Kidney problems Worth acting on Additional detail

    Castor Bean

    “Orally, chewing whole castor bean seeds can cause renal failure secondary to hypovolemia. Cellular damage to kidneys typically occurs 2-5 days after ingestion.”

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

    6 sources cited
    1. 5611. Challoner KR, McCarron MM. Castor bean intoxication. Ann Emerg Med 1990;19:1177-83. PubMed
    2. 5612. Palatnick W, Tenenbein M. Hepatotoxicity from castor bean ingestion in a child. J Toxicol Clin Toxicol 2000;38:67-9. PubMed
    3. 92998. Ferguson TS. Castor bean ingestion and ricin toxicity in a case of attempted suicide. West Indian Med J 2011;60(5):596.
    4. 93000. Kamath JV, Rana AC, Chowdhury AR. Pro-healing effect of Cinnamomum zeylanicum bark. Phytother Res 2003;17(8):970-2.
    5. 93505. Thornton SL, Darracq M, Lo J, et al. Castor bean seed ingestions: a state-wide poison control system's experience. Clin Toxicol (Phila) 2014;52(4):265-8. PubMed
    6. 93507. Worbs S, Köhler K, Pauly D, et al. Ricinus communis intoxications in human and veterinary medicine-a summary of real cases. Toxins (Basel) 2011;3(10):1332-72. PubMed

    Famciclovir

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

  • A severe allergic reaction Worth acting on Additional detail

    Castor Bean

    “Exposure to castor beans, plants, or seed dust can cause contact dermatitis and anaphylaxis in sensitive individuals. Castor oil does not appear to cause these effects. In one case report, a child developed cheilitis over the course of 3 weeks, which was determined to be an allergic reaction to castor oil contained in lip balm. Orally, castor oil did not cause rash in clinical research.”

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

    3 sources cited
    1. 5611. Challoner KR, McCarron MM. Castor bean intoxication. Ann Emerg Med 1990;19:1177-83. PubMed
    2. 103864. Sánchez-Herrero A, Mateos-Mayo A, Rodríguez-Lomba E, et al. Allergic contact cheilitis in an adolescent to Ricinus communis seed oil (castor oil) in a lip balm. Contact Dermatitis. 2018;79(3):176-178.
    3. 40185. Strates, B. S. and Hofmann, L. M. A randomized study of two preparations for large bowel radiology. Pharmatherapeutica 1987;5(1):57-61.

    Famciclovir

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

  • An allergic reaction Worth acting on Additional detail

    Castor Bean

    “Topically, the castor plant, crushed castor seeds, or castor seed dust can cause dermatitis in some patients. Castor oil does not appear to cause these effects. In one case report, a child developed cheilitis over the course of 3 weeks, which was determined to be an allergic reaction to castor oil contained in lip balm.”

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

    2 sources cited
    1. 5611. Challoner KR, McCarron MM. Castor bean intoxication. Ann Emerg Med 1990;19:1177-83. PubMed
    2. 103864. Sánchez-Herrero A, Mateos-Mayo A, Rodríguez-Lomba E, et al. Allergic contact cheilitis in an adolescent to Ricinus communis seed oil (castor oil) in a lip balm. Contact Dermatitis. 2018;79(3):176-178.

    Famciclovir

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

  • Stomach pain / Nausea Additional detail

    Castor Bean

    “Intravenously, castor bean extract can cause multi-organ failure and death. In one case report, a 26-year-old male presented to the emergency room with severe abdominal cramps, nausea, and headache after intravenously injecting castor bean extract as a suicide attempt.”

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

    6 sources cited
    1. 100835. Verougstraete N, Helsloot D, Deprez C, Heylen O, Casier I, Croes K. Lethal Injection of a Castor Bean Extract: Ricinine Quantification as a Marker for Ricin Exposure Using a Validated LC-MS/MS Method. J Anal Toxicol. 2019;43(3):e1-e5. PubMed
    2. 5611. Challoner KR, McCarron MM. Castor bean intoxication. Ann Emerg Med 1990;19:1177-83. PubMed
    3. 5612. Palatnick W, Tenenbein M. Hepatotoxicity from castor bean ingestion in a child. J Toxicol Clin Toxicol 2000;38:67-9. PubMed
    4. 92998. Ferguson TS. Castor bean ingestion and ricin toxicity in a case of attempted suicide. West Indian Med J 2011;60(5):596.
    5. 93000. Kamath JV, Rana AC, Chowdhury AR. Pro-healing effect of Cinnamomum zeylanicum bark. Phytother Res 2003;17(8):970-2.
    6. 93505. Thornton SL, Darracq M, Lo J, et al. Castor bean seed ingestions: a state-wide poison control system's experience. Clin Toxicol (Phila) 2014;52(4):265-8. PubMed

    Famciclovir

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

  • Dizziness Additional detail

    Castor Bean

    “Orally, castor oil has been associated with syncope or dizziness in 2-20% of patients in clinical research. In a study of women taking castor seeds as a contraceptive, there were some reports of headache.”

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

    5 sources cited
    1. 40188. Present, A. J., Jansson, B., Burhenne, H. J., Dodd, G. D., Goldberg, H. I., Goldstein, H. M., Miller, R. E., Nelson, J. A., and Stewart, E. T. Evaluation of 12 colon-cleansing regimens with single-contrast barium enema. AJR Am.J Roentgenol. 1982;139(5):8 PubMed
    2. 40163. 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
    3. 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
    4. 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
    5. 7128. 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.

    Famciclovir

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

  • Diarrhea / Vomiting 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

    Famciclovir

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

  • A skin rash Additional detail

    Castor Bean

    Recorded for Castor Bean in the same Natural Medicines adverse-effect record shown under A severe allergic reaction above.

    Famciclovir

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

  • Headache Additional detail

    Castor Bean

    Recorded for Castor Bean in the same Natural Medicines adverse-effect record shown under Dizziness above.

    Famciclovir

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

Reported for Castor Bean but not commonly for Famciclovir: bleeding in the gut, an electrolyte imbalance, stomach upset and shortness of breath.

Effects for Famciclovir come from the ADVERSE REACTIONS section of its FDA label; effects for Castor Bean come from the Natural Medicines adverse-effect record, quoted above. 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

From our Q&A

Questions About Castor Bean or Famciclovir

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Castor Bean or Famciclovir, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Famciclovir

This page covers Castor Bean only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Famciclovir page lists 17 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Coffee Charcoal (moderate), European Mandrake (moderate), Glucomannan (moderate) and Guar Gum (moderate).

By severity: 1 major · 7 moderate · 9 minor.

From our pharmacist’s overview on the Famciclovir page

“Famciclovir (Famvir) treats herpes infections like shingles and cold sores, and it only works if enough of the drug gets absorbed from your gut, which is exactly where every supplement on this list can interfere. The entry I would take most seriously is activated charcoal, the lone major-rated interaction, because charcoal binds medica…”

Reviewed by 2 · Jul 18, 2026

Open the Famciclovir interaction page

How much people look this up

Where Castor Bean and Famciclovir 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

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

29 days ago today
Medication Famciclovir
Top half

#1,021 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 27, 2026. The Castor Bean and Famciclovir 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 Famciclovir

What Is Famciclovir Used For?

Brand name: Famvir

Famciclovir treats infections caused by herpes viruses in adults. It is used for recurrent cold sores (herpes labialis), recurrent genital herpes and shingles (herpes zoster).

It can also be used for suppressive therapy, which means daily treatment to help prevent recurrent genital herpes outbreaks. In adults with HIV, it treats recurrent episodes of cold sores around the mouth (orolabial herpes) or genital herpes.

See full Famciclovir 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
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
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 Famciclovir Together: Common Questions

Is it safe to take Castor Bean with Famciclovir?
We do not list a known interaction between Castor Bean and Famciclovir. 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 Famciclovir have any of the same side effects?
Yes — our sources link each of them separately to 10 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.
How was the Castor Bean and Famciclovir combination checked?
Interactions in our licensed database are recorded against drug classes. Famciclovir is filed under 1 classification, and Castor Bean has documented interactions with 1 drug class — none of Famciclovir'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 — Famciclovir 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 Famciclovir interact with any supplements?
Yes. Famciclovir has documented interactions with 17 supplements in our database — Castor Bean is not one of them. The Famciclovir interaction page linked on this page lists every one, ranked by severity.

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

Still Have a Question About Famciclovir 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.