Drug & supplement interaction

Black Tea + Grepafloxacin

Grepafloxacin brand name: Raxar.

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

Grepafloxacin falls into 2 drug categories that Black Tea can interact with; the most serious is rated moderate. Theoretically, black tea might reduce the absorption of organic anion-transporting polypeptide (OATP) substrates.

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

Black Tea and Grepafloxacin

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

Why Are There 2 Interactions?

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

Moderate

ORGANIC ANION-TRANSPORTING POLYPEPTIDE SUBSTRATES (OATP)

1 of 2

Why this applies to Grepafloxacin

Grepafloxacin falls under ORGANIC ANION-TRANSPORTING POLYPEPTIDE SUBSTRATES (OATP) — the group Black Tea interacts with.

Theoretically, black tea might reduce the absorption of organic anion-transporting polypeptide (OATP) substrates.
In vitro, black tea extract inhibits organic anion-transporting polypeptide (OATP)2B1. OATP2B1 is expressed in the small intestine and liver and is responsible for the uptake of drugs and other compounds. In an animal model, black tea extract was found to inhibit the absorption of rosuvastatin, a substrate of OATP2B1. However, this effect has not been reported in humans.
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 grepafloxacin (the antibiotic once sold as Raxar). Black tea contains plant compounds that, in a test tube, can block a gut transporter called OATP2B1 that helps shuttle certain drugs from your intestine into your bloodstream. If grepafloxacin relies on that same doorway, sipping strong tea around the time you take it could, in theory, mean a bit less of the drug gets absorbed. Less antibiotic in your system could mean it works less well against the infection.

I want to be straight with you, though: this is based only on lab and animal data, and it hasn't actually been shown in people. It's a theoretical concern, not a proven problem. Still, it's a fair question for your pharmacist or doctor, who can confirm how best to time things.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Kondo A, Narumi K, Okuhara K, et al. Black tea extract and theaflavin derivatives affect the pharmacokinetics of rosuvastatin by modulating organic anion transporting polypeptide (OATP) 2B1 activity. Biopharm Drug Dispos. 2019;40(8):302-306. PubMed
Moderate

QUINOLONE ANTIBIOTICS

2 of 2

Grepafloxacin also falls under QUINOLONE ANTIBIOTICS.

Theoretically, quinolone antibiotics might increase the levels and adverse effects of caffeine.
Black tea contains caffeine. Concomitant use of caffeine and quinolones can decrease caffeine clearance and increase effects and risk of adverse effects.
Severity Moderate Likelihood Probable Evidence B

Interaction 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..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the thing to know if you're sipping black tea while on grepafloxacin (Raxar): this antibiotic can slow down how your body clears caffeine. The drug itself isn't the problem here, it's the caffeine in your tea that hangs around longer than usual. So the same cup that normally wouldn't faze you might hit harder.

In real life, that can mean feeling jittery, a racing or pounding heart, trouble sleeping, or a touch of anxiety or stomach upset. It's not dangerous for most healthy people, but it can be uncomfortable, especially if you're sensitive to caffeine or drink several cups a day. If you notice these feelings, it's reasonable to cut back on caffeinated drinks while you're on the antibiotic. As always, check with your pharmacist or doctor before changing anything.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Harder S, Fuhr U, Staib AH, Wolff T. Ciprofloxacin-caffeine: a drug interaction established using in vivo and in vitro investigations. Am J Med 1989;87:89S-91S. PubMed
  2. Carbo M, Segura J, De la Torre R, et al. Effect of quinolones on caffeine disposition. Clin Pharmacol Ther 1989;45:234-40. PubMed
  3. Healy DP, Polk RE, Kanawati L, et al. Interaction between oral ciprofloxacin and caffeine in normal volunteers. Antimicrob Agents Chemother 1989;33:474-8. PubMed
  4. Stille, W., Harder, S., Mieke, S., Beer, C., Shah, P. M., Frech, K., and Staib, A. H. Decrease of caffeine elimination in man during co-administration of 4-quinolones. J.Antimicrob.Chemother. 1987;20(5):729-734. PubMed
  5. Harder S, Staib AH, Beer C, et al. 4-quinolones inhibit biotransformation of caffeine. Eur J Clin Pharmacol 1988;35:651-6. PubMed
  6. Zhang LL, Zhang JR, Guo K, et al. Effects of fluoroquinolones on CYP4501A and 3A in male broilers. Res Vet Sci 2011;90:99-105. PubMed
  7. Cesana M, Broccali G, Imbimbo BP, Crema A. Effect of single doses of rufloxacin on the disposition of theophylline and caffeine after single administration. Int J Clin Pharmacol Ther Toxicol 1991:29:133-8.

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

Black Tea Also Interacts With Other Medications

Black Tea has 8 major, 571 moderate, 114 minor known drug interactions in our database — the Grepafloxacin one above is among them. If you take anything else, check it against the full list below.

Major 8 Moderate 571 Minor 114 No known interaction 2,137 (incl. Grepafloxacin)
Taking anything else?

Check Another of Your Medications Against Black Tea

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

Everything else you take

See Every Supplement That Interacts With Grepafloxacin

This page covers Black Tea only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Grepafloxacin page lists 164 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Apple (major), Arsenic (major) and Cesium (major).

By severity: 9 major · 113 moderate · 42 minor.

From our pharmacist’s overview on the Grepafloxacin page

“A week on grepafloxacin (Raxar), a quinolone antibiotic, often comes with juice at breakfast, coffee through the day, maybe a probiotic for the stomach, and each of those shows up on this list. The nine major entries among these 164 deserve your attention first: grapefruit and other fruit juices can block the transporter that carries t…”

Reviewed by 2 · Jul 18, 2026

Open the Grepafloxacin interaction page

One more smart check

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

We hold 271 real supplement products containing Black Tea, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Black Tea. Your product may carry other ingredients that interact with Grepafloxacin too, on top of Black Tea — 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 Black Tea and Grepafloxacin 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 Black Tea
Top 25%

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

29 days ago today
Medication Grepafloxacin
Steady interest

#2,419 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 Black Tea

What is Black Tea?

  • Mental alertness and energy
  • Heart health support
  • Blood pressure and cholesterol
  • Digestive complaints
  • Weight management
  • Antioxidant support

Black tea is a popular caffeinated drink made from the fully oxidized leaves of the Camellia sinensis plant, and it contains caffeine and antioxidant plant compounds. Moderate tea drinking is generally safe for most adults and may modestly support heart health and alertness, but it is not a proven treatment for any disease. If you are pregnant, breastfeeding, sensitive to caffeine, or taking medicines, talk to your pharmacist or doctor.

Read the full Black Tea monograph & all interactions
Keep checking

Other Drugs & Black Tea

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

8Major
571Moderate
114Minor
2,136No known interaction
8 Major 571 Moderate 114 Minor 2,136 No interaction
Major

8 interactions

Moderate

571 interactions

Showing 60 of 571 moderate interactions — see all 571 on the Black Tea page.

Minor

114 interactions

Showing 60 of 114 minor interactions — see all 114 on the Black Tea page.

No interaction 2,136 drugs checked — show the list

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

Showing the 60 most looked-up of 2,136 medications checked with no known interaction — see the full Black Tea list.

See the full Black Tea interactions page
See every supplement checked against Grepafloxacin, 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
Black Tea monograph › Uses, safety, and every drug interaction in one place Grepafloxacin supplement interactions › Every supplement checked against Grepafloxacin, 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 Black Tea and Grepafloxacin Together: Common Questions

Can you take Black Tea with Grepafloxacin?
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 Black Tea and Grepafloxacin?
Grepafloxacin belongs to more than one drug category, and Black Tea 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 Black Tea and Grepafloxacin 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 Grepafloxacin and Black Tea?

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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.