Drug & supplement interaction

Fennel + Cefprozil

Cefprozil brand name: Cefzil.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Fennel and Cefprozil in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Fennel and Cefprozil

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Cefprozil and Fennel in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Fennel safety at a glance

Fennel overall Use caution Generally safe as a food, but concentrated supplements and essential oil need more caution.
Pregnancy Possibly Unsafe When used orally. Observational research has found that regular use of fennel during pregnancy is associated with shortened gestation. Read the full pregnancy detail
Breastfeeding Possibly Unsafe When used orally. Case reports have linked consumption of an herbal tea containing extracts of fennel, licorice, anise, and goat's rue to neurotoxicity in two b... Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Cefprozil and Fennel? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Cefprozil

Interactions in our licensed database are recorded against drug classes, not just single drug names. Cefprozil is filed under 6 classifications — including organic anion transporter 3 (oat3) substrates, organic anion transporter 1 (oat1) substrates, antibiotic drugs. Fennel has documented interactions with 6 drug classes — the most serious being anticoagulant/antiplatelet drugs (moderate), ciprofloxacin (cipro) (moderate) and contraceptive drugs (moderate) — and none of Cefprozil’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Fennel Does Interact With Other Medications

Fennel has 740 moderate known drug interactions in our database — Cefprozil isn’t one of them. If you take anything else, check it against the full list below.

Moderate 740 No known interaction 2,090 (incl. Cefprozil)
Taking anything else?

Check Another of Your Medications Against Fennel

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

What to actually watch for

No Interaction Found — But Data Suggests Fennel and Cefprozil May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Vomiting / Nausea Additional detail

    Fennel

    “Orally, fennel may cause gastrointestinal complaints, including nausea and vomiting.”

    Fennel · Natural Medicines adverse-effect record, reported in nausea and vomiting.

    2 sources cited
    1. 19146. Cuzzolin L, Zaffani S, and Benoni G. Safety implications regarding use of phytomedicines. Eur.J Clin Pharmacol. 2006;62:37-42. PubMed
    2. 104196. Lee HW, Ang L, Lee MS, Alimoradi Z, Kim E. Fennel for reducing pain in primary dysmenorrhea: a systematic review and meta-analysis of randomized controlled trials. Nutrients 2020;12(11):3438. PubMed

    Cefprozil

    Listed in the ADVERSE REACTIONS section of the FDA label for Cefprozil. Read the label on DailyMed ›

Reported for Fennel but not commonly for Cefprozil: stomach upset, shortness of breath, an allergic reaction and a stuffy or runny nose.

Effects for Cefprozil come from the ADVERSE REACTIONS section of its FDA label; effects for Fennel come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 780 voluntary FDA FAERS reports for Cefprozil that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Fennel in Pregnancy & Breastfeeding

Pregnancy Possibly Unsafe

When used orally. Observational research has found that regular use of fennel during pregnancy is associated with shortened gestation.

Lactation Possibly Unsafe

When used orally. Case reports have linked consumption of an herbal tea containing extracts of fennel, licorice, anise, and goat's rue to neurotoxicity in two breast-feeding infants. The adverse effect was attributed to anethole, a constituent of fennel and anise. However, levels of anethole were not measured in breastmilk, and the herbal tea was not tested for contaminants. Furthermore, other adverse effects related to use of fennel during lactation have not been reported. However, until more is known, avoid using.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

Overlapping uses

What Cefprozil Is Prescribed For, and What Fennel Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Cefprozil is a prescription medicine with approved uses on its FDA label. Fennel is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Cefprozil is prescribed for: Cefprozil tablets and oral suspension are both used to treat mild to moderate bacterial infections in adults and children. Approved uses include pharyngitis/tonsillitis (strep throat), acute sinusitis, otitis media (ear infections), acute bacterial exacerbation of chronic bronchitis, and uncomplicated skin and skin-structure infections. Cefprozil tablets are also approved for secondary bacterial infection of acute bronchitis. Because antibiotic resistance is a real concern, cefprozil should only be used when the infection is proven or strongly suspected to be caused by bacteria that respond to it.

Fennel has been studied for:

  • Bronchitis studied, not established Fennel has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

    Fennel for bronchitis

    Although there has been interest in using oral fennel for bronchitis, there is insufficient reliable information about the clinical effects of fennel for this purpose.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Cefprozil on your own; if you are taking Fennel for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Fennel or Cefprozil

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

This page covers Fennel only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Cefprozil page lists 60 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Asarabacca (major), Siberian Cocklebur (major), African Wild Potato (moderate) and Aristolochia (moderate).

By severity: 3 major · 46 moderate · 11 minor.

From our pharmacist’s overview on the Cefprozil page

“Cefprozil (Cefzil) is a cephalosporin antibiotic, usually a short course for ear, sinus, throat, or skin infections, and three of the 60 supplements on this list warrant real caution even for a week of pills. Activated charcoal can bind the drug and pull it out of your system before it works.”

Reviewed by 2 · Jul 18, 2026

Open the Cefprozil interaction page

One more smart check

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

We hold 2,219 real supplement products containing Fennel, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Fennel. Even though Fennel itself has no known interaction with Cefprozil, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Fennel and Cefprozil 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 Fennel
Top 10%

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

29 days ago today
Medication Cefprozil
Steady interest

#1,640 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.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Fennel reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Fennel and Cefprozil records this page draws on were last updated July 11, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Fennel

What is Fennel?

Fennel
  • Digestive upset and bloating
  • Infant colic
  • Menstrual cramps
  • Cough and respiratory complaints
  • Breast milk support (traditional)

Fennel is a Mediterranean herb widely used as a food and spice, and traditionally taken for digestive complaints, colic, and menstrual cramps. Some small studies suggest possible benefit for certain stomach and menstrual symptoms, but the evidence is limited. It is generally well tolerated in food amounts, but concentrated supplements and the essential oil should be used with caution and after checking with your pharmacist or doctor.

Foeniculum vulgare · Apiaceae · Seeds (fruit), bulb, leaves, and essential oil · Tea, capsules, seeds, essential oil, extracts, and as a food/spice

An interaction check asks whether these two react with each other — it does not ask whether Fennel is a good idea for someone in your situation. Here is what our Fennel record says about it on its own.

Fennel: dosing

There is no single official or standardized dose for fennel as a supplement. The right amount depends on the form (tea, seeds, capsule, or oil) and the product.The best approach is to follow the directions on the product label and not exceed them.

From our Fennel monograph — the full record covers uses, side effects and every documented interaction.

Read the full Fennel monograph & all interactions
Medication

About Cefprozil

What Is Cefprozil Used For?

Brand name: Cefzil

Cefprozil tablets and oral suspension are both used to treat mild to moderate bacterial infections in adults and children. Approved uses include pharyngitis/tonsillitis (strep throat), acute sinusitis, otitis media (ear infections), acute bacterial exacerbation of chronic bronchitis, and uncomplicated skin and skin-structure infections.

Cefprozil tablets are also approved for secondary bacterial infection of acute bronchitis. Because antibiotic resistance is a real concern, cefprozil should only be used when the infection is proven or strongly suspected to be caused by bacteria that respond to it.

Most-Reported Side Effects for Cefprozil

From FAERS, the FDA’s public side-effect reporting system (780 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Chronic kidney disease 89 reports
Drug hypersensitivity 73 reports
Cough 64 reports
Acute kidney injury 59 reports
Dyspnea 59 reports
See full Cefprozil drug information
Keep checking

Other Drugs & Fennel

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

0Major
740Moderate
0Minor
2,089No known interaction
740 Moderate 2,089 No interaction
Moderate

740 interactions

Showing 60 of 740 moderate interactions — see all 740 on the Fennel page.

No interaction 2,089 drugs checked — show the list

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

Showing the 60 most looked-up of 2,089 medications checked with no known interaction — see the full Fennel list.

See the full Fennel interactions page
See every supplement checked against Cefprozil, ranked by severity
Evidence & sources

Fennel References

The 17 references that drive our Fennel monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996.
  2. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  3. Zhu M, Wong PY, Li RC. Effect of oral administration of fennel (Foeniculum vulgare) on ciprofloxacin absorption and disposition in the rat. J Pharm Pharmacol 1999;51:1391-6.
  4. Gral N, Beani JC, Bonnot D, et al. [Plasma levels of psoralens after celery ingestion]. Ann Dermatol Venereol 1993;120:599-603.
  5. Burkhard PR, Burkhardt K, Haenggeli CA, Landis T. Plant-induced seizures: reappearance of an old problem. J Neurol 1999;246:667-70. PubMed
  6. Rosti L, Nardini A, Bettinelli ME, Rosti D. Toxic effects of a herbal tea mixture in two newborns. Acta Paediatrica 1994;83:683. PubMed
  7. Cuzzolin L, Zaffani S, and Benoni G. Safety implications regarding use of phytomedicines. Eur.J Clin Pharmacol. 2006;62:37-42. PubMed
  8. Tognolini, M., Ballabeni, V., Bertoni, S., Bruni, R., Impicciatore, M., and Barocelli, E. Protective effect of Foeniculum vulgare essential oil and anethole in an experimental model of thrombosis. Pharmacol.Res 2007;56(3):254-260. PubMed
  9. Subehan, Usia, T., Iwata, H., Kadota, S., and Tezuka, Y. Mechanism-based inhibition of CYP3A4 and CYP2D6 by Indonesian medicinal plants. J Ethnopharmacol. 5-24-2006;105(3):449-455. PubMed
  10. Tognolini, M., Barocelli, E., Ballabeni, V., Bruni, R., Bianchi, A., Chiavarini, M., and Impicciatore, M. Comparative screening of plant essential oils: phenylpropanoid moiety as basic core for antiplatelet activity. Life Sci. 2-23-2006;78(13):1419-1432. PubMed
  11. Subehan, Zaidi, S. F., Kadota, S., and Tezuka, Y. Inhibition on human liver cytochrome P450 3A4 by constituents of fennel (Foeniculum vulgare): identification and characterization of a mechanism-based inactivator. J Agric.Food Chem. 12-12-2007;55(25):101 PubMed
  12. LEVY, S. B. Bronchial asthma due to ingestion of fennel and fennel seed. Ann.Allergy 1948;6(4):415.
  13. Ottolenghi, A., De Chiara, A., Arrigoni, S., Terracciano, L., and De Amici, M. [Diagnosis of food allergy caused by fruit and vegetables in children with atopic dermatitis]. Pediatr Med Chir 1995;17(6):525-530.
  14. Trabace L, Tucci P, Ciuffreda L, et al. "Natural" relief of pregnancy-related symptoms and neonatal outcomes: above all do no harm. J Ethnopharmacol. 2015;174:396-402. PubMed
  15. Denaxa D, Arkwright PD. Fennel as a cause of immediate hypersensitivity to toothpaste. Ann Allergy Asthma Immunol. 2020;125(1):99-100. PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Fennel and Cefprozil Together: Common Questions

Is it safe to take Fennel with Cefprozil?
We do not list a known interaction between Fennel and Cefprozil. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Fennel and Cefprozil have any of the same side effects?
Yes — our sources link each of them separately to 2 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
Are Fennel and Cefprozil used for the same thing?
They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Fennel in each. That is a conversation for your prescriber, especially if Cefprozil is being adjusted to a target.
How was the Fennel and Cefprozil combination checked?
Interactions in our licensed database are recorded against drug classes. Cefprozil is filed under 6 classifications, and Fennel has documented interactions with 6 drug classes — none of Cefprozil's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Fennel interact with any other medications?
Yes. Fennel has 740 documented drug interactions in our database — Cefprozil is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Cefprozil interact with any supplements?
Yes. Cefprozil has documented interactions with 60 supplements in our database — Fennel is not one of them. The Cefprozil interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Fennel monograph Uses, safety profile, and every drug interaction in one place Cefprozil drug information The full plain-English guide to this medication Cefprozil supplement interactions Every supplement checked against Cefprozil, 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 References The 17 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Cefprozil and Fennel?

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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.