Drug & supplement interaction

Calamus + Felodipine

Felodipine brand names: Plendil, Renedil.

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

Felodipine falls into 2 drug categories that Calamus can interact with; the most serious is rated moderate. Theoretically, taking calamus with other antihypertensive medications might increase the risk of hypotension.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Calamus and Felodipine

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Calamus interacts with whole categories of medication. Felodipine falls into 2 of those categories, so it can interact with Calamus in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

ANTIHYPERTENSIVE DRUGS

1 of 2

Why this applies to Felodipine

Felodipine falls under ANTIHYPERTENSIVE DRUGS — the group Calamus interacts with.

Theoretically, taking calamus with other antihypertensive medications might increase the risk of hypotension.
Animal research shows that calamus decreases the rate and strength of the heartbeat, which might lower blood pressure. use with caution.
Severity Moderate 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 simple version: Felodipine is a calcium channel blocker that already lowers your blood pressure by relaxing your blood vessels. Calamus, based on animal studies, may slow the heart a bit and nudge blood pressure down on its own. Stack the two together and you could, in theory, push your blood pressure lower than intended.

If that happened, you might feel dizzy, lightheaded, tired, or get a headache, especially when standing up quickly. I'll be honest though, this concern comes from lab and animal research, not solid human studies, so it's more of a caution than a proven problem. Calamus also carries its own safety baggage (the FDA banned it from foods). I'd skip it and check with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. 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.
Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

2 of 2

Felodipine also falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES.

Theoretically, taking calamus with drugs metabolized by CYP3A4 might increase drug levels and potentially increase the risk of adverse effects.
In vitro research shows that calamus extract inhibits CYP3A4 enzyme.
Severity Moderate 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

Your body relies on a liver enzyme called CYP3A4 to break down felodipine. Lab studies suggest calamus may slow that enzyme down. If that happens in people, felodipine could clear out more slowly and build up in your bloodstream, which can make its blood-pressure-lowering effect stronger than intended. You might notice things like dizziness, lightheadedness when standing, flushing, headache, swelling in your ankles, or a faster heartbeat.

That said, this is only a theoretical concern based on test-tube research, not human studies, so we honestly don't know how much it matters in real life. Calamus also carries its own safety worries, which is why I'd lean toward avoiding it. Before combining the two, please check with your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. 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.

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 1,097 moderate, 19 minor known drug interactions in our database — the Felodipine one above is among them. If you take anything else, check it against the full list below.

Moderate 1,097 Minor 19 No known interaction 1,714 (incl. Felodipine)
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 Felodipine

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 Felodipine, 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 Felodipine

This page covers Calamus only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Felodipine page lists 232 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), American Mistletoe (major), Coleus (major) and Grapefruit (major).

By severity: 8 major · 182 moderate · 42 minor.

From our pharmacist’s overview on the Felodipine page

“Felodipine (Plendil) is a blood pressure medicine broken down by the CYP3A4 enzyme, which is why 232 supplements and foods have an interaction on file, eight of them rated major. This list deserves real care.”

Reviewed by 2 · Jul 18, 2026

Open the Felodipine 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 Felodipine 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 Felodipine 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

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

29 days ago today
Medication Felodipine
Steady interest

#1,637 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 Felodipine

What Is Felodipine Used For?

Brand names: Plendil, Renedil

Felodipine extended-release tablets are used to treat high blood pressure (hypertension). Lowering blood pressure reduces the risk of serious events like stroke and heart attack. Felodipine may be used alone or combined with other blood pressure medicines.

Keeping blood pressure under control is part of a broader approach to heart health that can include managing cholesterol, blood sugar, and lifestyle factors like diet, exercise, and not smoking.

See full Felodipine 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
1,097Moderate
19Minor
1,713No known interaction
1,097 Moderate 19 Minor 1,713 No interaction
Moderate

1,097 interactions

Showing 60 of 1,097 moderate interactions — see all 1,097 on the Calamus page.

Minor

19 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 Felodipine, 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 Felodipine supplement interactions › Every supplement checked against Felodipine, ranked by severity Felodipine 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 Felodipine Together: Common Questions

Can you take Calamus with Felodipine?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Calamus and Felodipine?
Felodipine belongs to more than one drug category, and Calamus interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Calamus and Felodipine interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Felodipine 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.