Drug & supplement interaction

Calamus + Cimetidine

Cimetidine brand names: Tagamet HB, Tagamet, Cimetidine Injection.

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

Calamus has a minor interaction with Cimetidine. Theoretically, taking calamus might reduce the effectiveness of H2-blockers.

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

Calamus and Cimetidine

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

Minor

H2-BLOCKERS

Why this applies to Cimetidine

Cimetidine falls under H2-BLOCKERS — the group Calamus interacts with.

Theoretically, taking calamus might reduce the effectiveness of H2-blockers.
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 with cimetidine (Tagamet) and calamus. Cimetidine works by calming down acid production in your stomach, which is how it eases heartburn, reflux, and ulcer pain. The concern on file is that calamus may actually lower your stomach's pH, meaning it could nudge things back toward more acid. If that happens, cimetidine might not control your symptoms as well, and you could notice more burning or indigestion creeping back.

I want to be honest about how shaky this is: it's mostly theoretical and based on weak, anecdotal evidence, not strong human studies. Beyond that, calamus has its own safety red flags (the FDA banned it from foods), so I'd steer clear of it for that reason alone. Please run any supplement past your pharmacist or doctor before mixing it in.

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 1,098 moderate, 18 minor known drug interactions in our database — the Cimetidine one above is one of them. If you take anything else, check it against the full list below.

Moderate 1,098 Minor 18 No known interaction 1,714 (incl. Cimetidine)
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.

From our Q&A

Questions About Calamus or Cimetidine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Calamus or Cimetidine, 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 Cimetidine

This page covers Calamus only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Cimetidine page lists 95 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Pu-erh Tea (major), St. John's Wort (major), Adrafinil (moderate) and African Wild Potato (moderate).

By severity: 3 major · 63 moderate · 29 minor.

Open the Cimetidine 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 Cimetidine 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 Cimetidine 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
Steady interest

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

29 days ago today
Medication Cimetidine
Steady interest

#1,905 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
Medication

About Cimetidine

What Is Cimetidine Used For?

Brand names: Tagamet HB, Tagamet, Cimetidine Injection

Cimetidine tablets sold over the counter — including brands like Acid Controller, Acid Reducer, Basic Care Acid Reducer, Equate Cimetidine, and cimetidine 200 — are used to relieve heartburn associated with acid indigestion and sour stomach, and to prevent heartburn brought on by eating or drinking certain foods and beverages.

Prescription-strength cimetidine tablets and Cimetidine Hydrochloride Oral Solution are used for more serious conditions: short-term treatment of active duodenal ulcers (ulcers in the upper small intestine) and benign gastric ulcers (stomach ulcers), maintenance therapy to keep duodenal ulcers from coming back, healing of erosive GERD (acid reflux that has damaged the lining of the esophagus), and treatment of conditions that cause the stomach to make too much acid — such as Zollinger-Ellison Syndrome, systemic mastocytosis, and multiple endocrine adenomas.

See full Cimetidine 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
18Minor
1,713No known interaction
1,098 Moderate 18 Minor 1,713 No interaction
Moderate

1,098 interactions

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

Minor

18 interactions

No interaction 1,713 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 1,713 medications checked with no known interaction — see the full Calamus list.

See the full Calamus interactions page
See every supplement checked against Cimetidine, 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 Cimetidine supplement interactions › Every supplement checked against Cimetidine, ranked by severity Cimetidine drug information › The full plain-English guide to this medication 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 Cimetidine Together: Common Questions

Can you take Calamus with Cimetidine?
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 Cimetidine 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 Cimetidine 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.