Drug & supplement interaction

Calamus + Bismuth Subcarbonate, Calcium Carbonate, Opium

Bismuth Subcarbonate, Calcium Carbonate, Opium brand name: Diabismul.

Minor Interaction
Medically reviewed by · Updated October 2026
The bottom line Minor

Calamus has a minor interaction with Bismuth Subcarbonate, Calcium Carbonate, Opium. Theoretically, taking calamus might reduce the effectiveness of antacids.

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

Calamus and Bismuth Subcarbonate, Calcium Carbonate, Opium

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

Minor

ANTACIDS

Why this applies to Bismuth Subcarbonate, Calcium Carbonate, Opium

Bismuth Subcarbonate, Calcium Carbonate, Opium falls under ANTACIDS — the group Calamus interacts with.

Theoretically, taking calamus might reduce the effectiveness of antacids.
Some research suggests that calamus lowers gastric pH.
Severity Minor 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 gist for your combo product (which includes calcium carbonate as the antacid piece, plus bismuth and a small amount of opium for diarrhea and upset stomach). Some early research hints that calamus may slightly lower your stomach's pH, meaning it makes things a touch more acidic. Since the calcium carbonate part works by neutralizing stomach acid, calamus could in theory nudge against that and make your antacid a bit less effective for things like heartburn or sour stomach.

I'll be honest, this is theoretical and based only on weak, anecdotal evidence, so it's not something to lose sleep over. That said, calamus has real safety concerns of its own, so I'd skip it and chat with your pharmacist if you're considering it.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 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

Calamus Also Interacts With Other Medications

Calamus has 1,100 moderate, 18 minor known drug interactions in our database — the Bismuth Subcarbonate, Calcium Carbonate, Opium one above is one of them. If you take anything else, check it against the full list below.

Moderate 1,100 Minor 18 No known interaction 1,712 (incl. Bismuth Subcarbonate, Calcium Carbonate, Opium)
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.

Everything else you take

See Every Supplement That Interacts With Bismuth Subcarbonate, Calcium Carbonate, Opium

This page covers Calamus only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Bismuth Subcarbonate, Calcium Carbonate, Opium page lists 30 supplements it has a documented interaction with, worst first, each one explained.

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

By severity: 1 major · 10 moderate · 19 minor.

From our pharmacist’s overview on the Bismuth Subcarbonate, Calcium Carbonate, Opium page

“Diabismul (bismuth subcarbonate, calcium carbonate, and opium) is an older antidiarrheal, and its supplement interactions deserve real attention, starting with activated charcoal, the single major-rated entry on this page. Charcoal binds a wide swath of medicines in the gut and can sharply cut how much your body absorbs.”

Reviewed by 2 · Jul 18, 2026

Open the Bismuth Subcarbonate, Calcium Carbonate, Opium 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. Your product may carry other ingredients that interact with Bismuth Subcarbonate, Calcium Carbonate, Opium too, on top of Calamus — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Calamus and Bismuth Subcarbonate, Calcium Carbonate, Opium 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

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

29 days ago today
Medication Bismuth Subcarbonate, Calcium Carbonate, Opium
Top 5%

#63 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 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.

Read the full Calamus monograph & all interactions
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
1,100Moderate
18Minor
1,711No known interaction
1,100 Moderate 18 Minor 1,711 No interaction
Moderate

1,100 interactions

Showing 60 of 1,100 moderate interactions — see all 1,100 on the Calamus page.

Minor

18 interactions

No interaction 1,711 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 1,711 medications checked with no known interaction — see the full Calamus list.

See the full Calamus interactions page
See every supplement checked against Bismuth Subcarbonate, Calcium Carbonate, Opium, 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
Calamus monograph › Uses, safety, and every drug interaction in one place Bismuth Subcarbonate, Calcium Carbonate, Opium supplement interactions › Every supplement checked against Bismuth Subcarbonate, Calcium Carbonate, Opium, 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 Calamus and Bismuth Subcarbonate, Calcium Carbonate, Opium Together: Common Questions

Can you take Calamus with Bismuth Subcarbonate, Calcium Carbonate, Opium?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Calamus and Bismuth Subcarbonate, Calcium Carbonate, Opium interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

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

Still Have a Question About Bismuth Subcarbonate, Calcium Carbonate, Opium 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.