Drug & supplement interaction

Theaflavin + Gemifloxacin

Gemifloxacin brand name: Factive.

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

Theaflavin has a moderate interaction with Gemifloxacin. In vitro, theaflavin inhibits organic anion-transporting polypeptide (OATP)2B1.

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

Theaflavin and Gemifloxacin

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

Moderate

ORGANIC ANION-TRANSPORTING POLYPEPTIDE SUBSTRATES (OATP)

Why this applies to Gemifloxacin

Gemifloxacin falls under ORGANIC ANION-TRANSPORTING POLYPEPTIDE SUBSTRATES (OATP) — the group Theaflavin interacts with.

In vitro, theaflavin 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. This interaction has not been shown in humans. However, theaflavin might reduce the absorption of drugs that are OATP2B1 substrates. 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 gist for gemifloxacin (Factive). In a lab dish, theaflavin (a compound in black tea) blocked a gut transporter called OATP2B1 that helps pull certain drugs into your body. If gemifloxacin relies on that transporter, theaflavin could in theory lower how much antibiotic you absorb. Less drug in your system can mean a weaker punch against your pneumonia or bronchitis, which is the opposite of what you want when fighting an infection.

The honest part: this has only been seen in test tubes, never in people, so it's quite uncertain. A normal cup or two of black tea is unlikely to be a problem. If you're using concentrated theaflavin extracts, that's worth a quick chat with your pharmacist or doctor while you finish your antibiotic.

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

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

Theaflavin Also Interacts With Other Medications

Theaflavin has 129 moderate known drug interactions in our database — the Gemifloxacin one above is one of them. If you take anything else, check it against the full list below.

Moderate 129 No known interaction 2,701 (incl. Gemifloxacin)
Taking anything else?

Check Another of Your Medications Against Theaflavin

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

Everything else you take

See Every Supplement That Interacts With Gemifloxacin

This page covers Theaflavin only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Gemifloxacin page lists 81 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Apple (major), Grapefruit (major), Sweet Orange (major) and Bacillus Coagulans (moderate).

By severity: 4 major · 56 moderate · 21 minor.

From our pharmacist’s overview on the Gemifloxacin page

“Picture a week on gemifloxacin (Factive) for pneumonia or a stubborn bronchitis: juice with breakfast, a probiotic, maybe calcium. That ordinary morning is where the trouble sits, and this list warrants real care.”

Reviewed by 2 · Jul 18, 2026

Open the Gemifloxacin interaction page

One more smart check

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

We hold 11 real supplement products containing Theaflavin, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Theaflavin. Your product may carry other ingredients that interact with Gemifloxacin too, on top of Theaflavin — 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 Theaflavin and Gemifloxacin 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 Theaflavin
Steady interest

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

29 days ago today
Medication Gemifloxacin
Top half

#1,183 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 Theaflavin

What is Theaflavin?

  • Heart health and cholesterol support
  • Antioxidant support
  • Weight management
  • Blood sugar support
  • General wellness

Theaflavins are antioxidant compounds formed when tea leaves are oxidized to make black tea. Early research suggests they may help with cholesterol and provide antioxidant effects, but high-quality human evidence is limited and doses are not standardized. Drinking black tea is generally safe, but talk to your pharmacist or doctor before taking concentrated extracts.

Read the full Theaflavin monograph & all interactions
Medication

About Gemifloxacin

What Is Gemifloxacin Used For?

Brand name: Factive

  • Gemifloxacin is used to treat pneumonia. Gemifloxacin may also be used to treat bronchitis but should not be used for this condition if there are other treatment options. Gemifloxacin is in a class of antibiotics called fluoroquinolones. It works by killing bacteria that cause infections.

  • Antibiotics such as gemifloxacin do not work for colds, flu, or other viral infections. Using antibiotics when they are not needed increases your risk of getting an infection later that resists antibiotic treatment.

See full Gemifloxacin drug information
Keep checking

Other Drugs & Theaflavin

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

0Major
129Moderate
0Minor
2,700No known interaction
129 Moderate 2,700 No interaction
Moderate

129 interactions

Showing 60 of 129 moderate interactions — see all 129 on the Theaflavin page.

No interaction 2,700 drugs checked — show the list

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

Showing the 60 most looked-up of 2,700 medications checked with no known interaction — see the full Theaflavin list.

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

Can you take Theaflavin with Gemifloxacin?
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.
How serious is the Theaflavin and Gemifloxacin 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 Gemifloxacin and Theaflavin?

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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.