Drug & supplement interaction

White Pepper + Diltiazem

Diltiazem brand names: Cardizem, Cardizem SR, Diltiaz SR, Cardizem CD, Tiazac, and others.

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

Diltiazem falls into 2 drug categories that White Pepper can interact with; the most serious is rated moderate. In vitro evidence suggests that piperine, a constituent of white pepper, inhibits cytochrome P450 3A4 (CYP3A4).

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

White Pepper and Diltiazem

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

Why Are There 2 Interactions?

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

Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

1 of 2

Why this applies to Diltiazem

Diltiazem falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES — the group White Pepper interacts with.

In vitro evidence suggests that piperine, a constituent of white pepper, inhibits cytochrome P450 3A4 (CYP3A4). Theoretically, concomitant use with white pepper might increase the effects and side effects of drugs metabolized by CYP3A4.
Some drugs metabolized by CYP3A4 include some calcium channel blockers (diltiazem, nicardipine, verapamil), chemotherapeutic agents (etoposide, paclitaxel, vinblastine, vincristine, vindesine), antifungals (ketoconazole, itraconazole), glucocorticoids, cisapride (Propulsid), alfentanil (Alfenta), fentanyl (Sublimaze), losartan (Cozaar), fluoxetine (Prozac), midazolam (Versed), omeprazole (Prilosec), ondansetron (Zofran), propranolol (Inderal), fexofenadine (Allegra), and numerous others.
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 gist for diltiazem. Your liver uses an enzyme called CYP3A4 to break diltiazem down and keep its levels in check. Piperine, the spicy compound in white pepper, has shown in lab dish studies that it may slow that same enzyme. In theory, if diltiazem is cleared more slowly, more of it could build up in your blood, which might mean a bigger blood-pressure drop, a slower heart rate, dizziness, swelling in the ankles, or feeling unusually tired.

The reassuring part: this is theoretical, based on lab work, not real patient cases. Everyday pepper sprinkled on food is very unlikely to cause trouble. Concentrated piperine supplements are where I'd be more careful. If you're considering one, just run it by your pharmacist or doctor first.

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

P-GLYCOPROTEIN SUBSTRATES

2 of 2

Diltiazem also falls under P-GLYCOPROTEIN SUBSTRATES.

Theoretically, white pepper might increase levels of p-glycoprotein substrates. The piperine constituent of white pepper seems to inhibit p-glycoprotein in vitro.
Some drugs metabolized by p-glycoprotein include some chemotherapeutic agents (etoposide, paclitaxel, vinblastine, vincristine, vindesine), antifungals (ketoconazole, itraconazole), protease inhibitors (amprenavir, indinavir, nelfinavir, saquinavir), H2 antagonists (cimetidine, ranitidine), some calcium channel blockers (diltiazem, verapamil), digoxin, corticosteroids, erythromycin, cisapride (Propulsid), fexofenadine (Allegra), cyclosporine, loperamide (Imodium), quinidine, and others.
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 gist with white pepper and your diltiazem. The piperine in pepper may block a transporter called p-glycoprotein, which helps move drugs like diltiazem out of your body. If that transporter slows down, a bit more diltiazem could stay in your system. Since diltiazem already relaxes blood vessels and slows the heart, higher levels might mean a little extra of its usual effects, things like dizziness, low blood pressure, a slower pulse, flushing, or ankle swelling.

The honest part: this is theoretical, based only on lab studies, not real patients. Sprinkling pepper on your food almost certainly won't matter. The bigger question is concentrated piperine supplements, so check with your pharmacist or doctor before using one.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Bhardwaj RK, Glaeser H, Becquemont L, et al. Piperine, a major constituent of black pepper, inhibits human P-glycoprotein and CYP3A4. J Pharmacol Exp Ther 2002;302:645-50. PubMed
  2. Han, Y., Chin Tan, T. M., and Lim, L. Y. In vitro and in vivo evaluation of the effects of piperine on P-gp function and expression. Toxicol.Appl.Pharmacol. 8-1-2008;230(3):283-289. PubMed
  3. Aher, S., Biradar, S., Gopu, C. L., and Paradkar, A. Novel pepper extract for enhanced P-glycoprotein inhibition. J Pharm.Pharmacol. 2009;61(9):1179-1186. PubMed

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

White Pepper Also Interacts With Other Medications

White Pepper has 976 moderate, 3 minor known drug interactions in our database — the Diltiazem one above is among them. If you take anything else, check it against the full list below.

Moderate 976 Minor 3 No known interaction 1,851 (incl. Diltiazem)
Taking anything else?

Check Another of Your Medications Against White Pepper

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

From our Q&A

Questions About White Pepper or Diltiazem

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

This page covers White Pepper only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Diltiazem page lists 260 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: 7 major · 214 moderate · 39 minor.

From our pharmacist’s overview on the Diltiazem page

“Someone on diltiazem (Cardizem, Tiazac) is usually managing blood pressure, angina, or a fast heart rhythm, so this list deserves genuine care. Seven of the 260 ingredients on file carry a major rating, and two of those are things people actually buy: grapefruit, which blocks the enzyme that clears diltiazem and can push its blood leve…”

Reviewed by 2 · Jul 18, 2026

Open the Diltiazem interaction page

One more smart check

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

We hold 2 real supplement products containing White Pepper, each one broken down to its full ingredient list — and combination products often carry several ingredients besides White Pepper. Your product may carry other ingredients that interact with Diltiazem too, on top of White Pepper — 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 White Pepper and Diltiazem 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 White Pepper
Top half

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

29 days ago today
Medication Diltiazem
Top 25%

#341 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 White Pepper

What is White Pepper?

  • Digestive upset
  • Seasoning and appetite support
  • Cough and cold remedies (traditional)
  • Minor aches and pains (traditional)
  • Antimicrobial (traditional)

White pepper comes from the same plant as black pepper and is mostly used as a kitchen spice. In normal food amounts it is generally safe for most people, but there is little solid human research supporting its use as a medicine. Talk with your pharmacist or doctor before using concentrated supplements, especially if you are pregnant, breastfeeding, or have a health condition.

Read the full White Pepper monograph & all interactions
Medication

About Diltiazem

What Is Diltiazem Used For?

Brand names: Cardizem, Cardizem SR, Diltiaz SR, Cardizem CD, Tiazac, Diltiaz XT, Diltiaz CD, Dilacor, Diltiaz, Cardizem LA, Dilacor XR, Cartia XT, Tiamate, Adizem-SR, Adizem-XL, Angitil SR, Angitil XL, Calcicard CR, Dilcardia SR, Dilzem SR, Dilzem XL, Slozem, Tildiem LA, Tildiem Retard, Viazem XL, Zemtard 120XL, Zemtard 180XL, Zemtard 240XL, Zemtard 300XL

Oral extended-release diltiazem (capsules and tablets) treats high blood pressure (hypertension). It is also used for chronic stable angina, which is chest pain from the heart working harder than its blood supply allows. It can be used alone or with other blood pressure medicines.

Some extended-release capsule products, such as Cartia, Cartia Xt and certain generic diltiazem capsules, are also approved for angina due to coronary artery spasm. The intravenous (IV) injection is a different use: it gives temporary control of a rapid heart rate in atrial fibrillation or atrial flutter, and rapidly converts paroxysmal supraventricular tachycardia (PSVT) to normal rhythm.

See full Diltiazem drug information
Keep checking

Other Drugs & White Pepper

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

0Major
976Moderate
3Minor
1,850No known interaction
976 Moderate 3 Minor 1,850 No interaction
Moderate

976 interactions

Showing 60 of 976 moderate interactions — see all 976 on the White Pepper page.

Minor

3 interactions

No interaction 1,850 drugs checked — show the list

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

Showing the 60 most looked-up of 1,850 medications checked with no known interaction — see the full White Pepper list.

See the full White Pepper interactions page
See every supplement checked against Diltiazem, 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
White Pepper monograph › Uses, safety, and every drug interaction in one place Diltiazem supplement interactions › Every supplement checked against Diltiazem, ranked by severity Diltiazem 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 White Pepper and Diltiazem Together: Common Questions

Can you take White Pepper with Diltiazem?
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 White Pepper and Diltiazem?
Diltiazem belongs to more than one drug category, and White Pepper 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 White Pepper and Diltiazem 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 Diltiazem and White Pepper?

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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.