Drug & supplement interaction

Calamus + Entecavir

Entecavir brand name: Baraclude.

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 Calamus and Entecavir 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 Entecavir states a food rule worth keeping to, and 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

Calamus and Entecavir

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 Entecavir and Calamus 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.

Calamus safety at a glance

Calamus overall Avoid Some forms contain beta-asarone, a possible carcinogen banned from food by the FDA.
Pregnancy Likely Unsafe When used orally; avoid using. Read the full pregnancy detail
Breastfeeding Likely Unsafe When used orally; avoid using. Read the full breastfeeding detail

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 Entecavir and Calamus? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Entecavir

Interactions in our licensed database are recorded against drug classes, not just single drug names. Entecavir is filed under a single classification — oral drugs. Calamus has documented interactions with 10 drug classes — the most serious being anticholinergic drugs (moderate), antihypertensive drugs (moderate) and cholinergic drugs (moderate) — and none of Entecavir’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

Calamus Does Interact With Other Medications

Calamus has 1,098 moderate, 19 minor known drug interactions in our database — Entecavir isn’t one of them. If you take anything else, check it against the full list below.

Moderate 1,098 Minor 19 No known interaction 1,713 (incl. Entecavir)
Taking anything else?

Check Another of Your Medications Against Calamus

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

What to actually watch for

No Interaction Found — But Data Suggests Calamus and Entecavir 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.

  • Nausea Additional detail

    Calamus

    “A case of gastrointestinal toxicity has been reported in a 19-year-old male who appeared to use calamus root for its euphoric effects. The man ingested a large amount of the root with water and later presented at the emergency department with continuous vomiting, paleness, and sweating. He was treated intravenously with saline and promethazine.”

    Calamus · Natural Medicines adverse-effect record, reported in nausea and vomiting.

    3 sources cited
    1. 38458. Vargas, C. P., Wolf, L. R., Gamm, S. R., and Koontz, K. Getting to the root (Acorus calamus) of the problem. J Toxicol Clin Toxicol 1998;36(3):259-260.
    2. 93980. Björnstad K, Helander A, Hultén P, Beck O. Bioanalytical investigation of asarone in connection with Acorus calamus oil intoxications. J Anal Toxicol 2009;33(9):604-9. PubMed
    3. 33310. Shoba, F. G. and Thomas, M. Study of antidiarrhoeal activity of four medicinal plants in castor-oil induced diarrhoea. J Ethnopharmacol 2001;76(1):73-76. PubMed

    Entecavir

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

Reported for Calamus but not commonly for Entecavir: a fast or pounding heartbeat, vomiting and sweating.

Effects for Entecavir come from the ADVERSE REACTIONS section of its FDA label; effects for Calamus 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

Calamus in Pregnancy & Breastfeeding

Pregnancy And Lactation Likely Unsafe

When used orally; avoid using.

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

How to take them

Some Entecavir Products Have a Food Rule — Calamus Should Not Break It

At least one FDA label for a product containing Entecavir says to take it on an empty stomach. Most supplements — Calamus included — are taken with a meal, so the easy mistake is swallowing both together at breakfast. Where that rule applies, keep Entecavir on its own and move Calamus 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 Entecavir 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.

(2.1) 2.1 Timing of Administration BARACLUDE should be administered on an empty stomach (at least 2 hours after a meal and 2 hours before the next meal).

From the Dosage and Administration section of the FDA label we read for Entecavir — where that label names a specific product, the instruction is that product's. Read the label on DailyMed ›

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.

Overlapping uses

What Entecavir Is Prescribed For, and What Calamus Has Been Studied For

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

Entecavir is prescribed for: Entecavir treats chronic hepatitis B virus (HBV) infection in adults who have signs of active virus in their blood and liver inflammation or liver damage. It is used when lab tests show persistently elevated liver enzymes (ALT or AST) or when a liver biopsy confirms active disease. Baraclude (the brand oral solution and tablet) is also approved for children 2 years of age and older weighing at least 10 kg, with the same requirement for evidence of active viral replication and liver involvement. Generic entecavir tablets are indicated for adults; pediatric approval varies by specific product — check with your pharmacist or prescriber.

Calamus has been studied for:

  • Cancer studied, not established Calamus has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

    Calamus for cancer

    Although there has been interest in using oral calamus for cancer, there is insufficient reliable information about the clinical effects of calamus for this condition.

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 Entecavir on your own; if you are taking Calamus 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 Entecavir

This page covers Calamus only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Entecavir 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.

Open the Entecavir interaction page

One more smart check

Taking Calamus as Part of a Dietary Supplement Product? Check It for Interactions

We hold 71 real supplement products containing Calamus, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Calamus. Even though Calamus itself has no known interaction with Entecavir, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Calamus and Entecavir 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 Calamus
Top half

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

29 days ago today
Medication Entecavir
Top half

#1,239 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 Calamus reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Calamus and Entecavir records this page draws on were last updated July 10, 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 Calamus

What is Calamus?

Calamus
  • Digestive upset and gas
  • Loss of appetite
  • Memory and focus (traditional)
  • Coughs and colds
  • Calming or sedative effect (traditional)

Calamus is a swamp plant with a long history in Ayurvedic and traditional Chinese medicine, mostly for digestive and nervous-system complaints. However, it contains beta-asarone, a compound linked to cancer and other toxic effects in animal studies, which is why the U.S. FDA banned it from foods. Because of these safety concerns and a lack of solid human evidence, it is generally best avoided.

Acorus calamus · Acoraceae · Rhizome (root) and essential oil · Dried root, powder, tea, tincture, essential oil

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

Calamus: dosing

There is no established safe or effective dose for calamus. Because of the cancer and toxicity concerns, health authorities do not recommend a standard amount.If you come across a product that contains calamus, do not assume any amount is safe. For most people, the safest choice is to avoid calamus altogether and consider better-studied alternatives.

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

Read the full Calamus monograph & all interactions
Medication

About Entecavir

What Is Entecavir Used For?

Brand name: Baraclude

Entecavir treats chronic hepatitis B virus (HBV) infection in adults who have signs of active virus in their blood and liver inflammation or liver damage. It is used when lab tests show persistently elevated liver enzymes (ALT or AST) or when a liver biopsy confirms active disease.

Baraclude (the brand oral solution and tablet) is also approved for children 2 years of age and older weighing at least 10 kg, with the same requirement for evidence of active viral replication and liver involvement. Generic entecavir tablets are indicated for adults; pediatric approval varies by specific product — check with your pharmacist or prescriber.

See full Entecavir drug information
Keep checking

Other Drugs & Calamus

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

0Major
1,098Moderate
19Minor
1,712No known interaction
1,098 Moderate 19 Minor 1,712 No interaction
Moderate

1,098 interactions

Showing 60 of 1,098 moderate interactions — see all 1,098 on the Calamus page.

Minor

19 interactions

No interaction 1,712 drugs checked — show the list

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

Showing the 60 most looked-up of 1,712 medications checked with no known interaction — see the full Calamus list.

See the full Calamus interactions page
See every supplement checked against Entecavir, ranked by severity
Evidence & sources

Calamus References

The 13 references that drive our Calamus 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. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.
  2. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  3. Brinker F. Herb Contraindications and Drug Interactions. Sandy, OR: Eclectic Medical Publ, 1997.
  4. Shoba, F. G. and Thomas, M. Study of antidiarrhoeal activity of four medicinal plants in castor-oil induced diarrhoea. J Ethnopharmacol 2001;76(1):73-76. PubMed
  5. Koo, B. S., Park, K. S., Ha, J. H., Park, J. H., Lim, J. C., and Lee, D. U. Inhibitory effects of the fragrance inhalation of essential oil from Acorus gramineus on central nervous system. Biol Pharm.Bull. 2003;26(7):978-982. PubMed
  6. Oh, M. H., Houghton, P. J., Whang, W. K., and Cho, J. H. Screening of Korean herbal medicines used to improve cognitive function for anti-cholinesterase activity. Phytomedicine 2004;11(6):544-548. PubMed
  7. Panchal, G. M., Venkatakrishna-Bhatt, H., Doctor, R. B., and Vajpayee, S. Pharmacology of Acorus calamus L. Indian J Exp.Biol 1989;27(6):561-567.
  8. Vargas, C. P., Wolf, L. R., Gamm, S. R., and Koontz, K. Getting to the root (Acorus calamus) of the problem. J Toxicol Clin Toxicol 1998;36(3):259-260.
  9. Pandit S, Mukherjee PK, Ponnusankar S, Venkatesh M, Srikanth N. Metabolism mediated interaction of a-asarone and Acorus calamus with CYP3A4 and CYP2D6. Fitoterapia 2011;82(3):369-74.
  10. Sharma V, Singh I, Chaudhary P. Acorus calamus (The Healing Plant): a review on its medicinal potential, micropropagation and conservation. Nat Prod Res. 2014;28(18):1454-66.
  11. Björnstad K, Helander A, Hultén P, Beck O. Bioanalytical investigation of asarone in connection with Acorus calamus oil intoxications. J Anal Toxicol 2009;33(9):604-9. PubMed
  12. Federal Register. Volume 33, Page 6967. U.S. Government Publishing Office. http://api.fdsys.gov/link?collection=fr&volume=33&page=6967. Accessed May 23, 2018.
  13. Electronic Code of Federal Regulations. Title 21. Part 189 - Substances Prohibited From Use in Human Food. Available at: https://www.ecfr.gov/cgi-bin/text-idx?SID=259fa8a1284cad42676075c8425c7333&mc=true&node=pt21.3.189&rgn=div5.

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 Calamus and Entecavir Together: Common Questions

Is it safe to take Calamus with Entecavir?
We do not list a known interaction between Calamus and Entecavir. 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 Calamus and Entecavir 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.
Should I take Calamus and Entecavir at the same time of day?
At least one FDA label for a product containing Entecavir 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 Entecavir on its own and move Calamus 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.
Are Calamus and Entecavir 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 Calamus in each. That is a conversation for your prescriber, especially if Entecavir is being adjusted to a target.
How was the Calamus and Entecavir combination checked?
Interactions in our licensed database are recorded against drug classes. Entecavir is filed under 1 classification, and Calamus has documented interactions with 10 drug classes — none of Entecavir'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 Calamus interact with any other medications?
Yes. Calamus has 1,117 documented drug interactions in our database — Entecavir 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 Entecavir interact with any supplements?
Yes. Entecavir has documented interactions with 17 supplements in our database — Calamus is not one of them. The Entecavir 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

Calamus monograph Uses, safety profile, and every drug interaction in one place Entecavir drug information The full plain-English guide to this medication Entecavir supplement interactions Every supplement checked against Entecavir, 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 13 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Entecavir and Calamus?

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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.