Drug & supplement interaction

Eyebright + Granisetron

Granisetron brand names: Kytril, Sustol.

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 Eyebright and Granisetron 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 label for Granisetron states a food rule worth keeping to, and 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

Eyebright and Granisetron

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 Granisetron and Eyebright 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.

Eyebright safety at a glance

Eyebright overall Use caution Likely safe in small amounts as a tea, but using homemade or non-sterile preparations directly in the eye is risky.
Pregnancy Avoid Safety has not been established, so it is best avoided during pregnancy.
Breastfeeding Avoid There is not enough safety information, so avoid use while breastfeeding.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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

Why No Interaction Is Listed for Granisetron

Interactions in our licensed database are recorded against drug classes, not just single drug names. Granisetron is filed under 3 classifications — serotonergic drugs, serotonergic drugs, oral drugs. Eyebright has documented interactions with 1 drug class — the most serious being antidiabetes drugs (moderate) — and none of Granisetron’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

Eyebright Does Interact With Other Medications

Eyebright has 86 moderate known drug interactions in our database — Granisetron isn’t one of them. If you take anything else, check it against the full list below.

Moderate 86 No known interaction 2,744 (incl. Granisetron)
Taking anything else?

Check Another of Your Medications Against Eyebright

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

What to actually watch for

No Interaction Found — But Data Suggests Eyebright and Granisetron 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. One of them is worth acting on rather than waiting out — marked below.

  • Shortness of breath Worth acting on Additional detail

    Eyebright

    “Orally, eyebright has been reported to cause cough, dyspnea, and nasal congestion (4).”

    Eyebright · Natural Medicines adverse-effect record, reported in cough.

    1 source cited
    1. 4. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.

    Granisetron

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

  • Constipation / Nausea Additional detail

    Eyebright

    “Orally, eyebright has been reported to cause nausea and constipation (4).”

    Eyebright · Natural Medicines adverse-effect record, reported in constipation.

    1 source cited
    1. 4. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.

    Granisetron

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

  • Headache Additional detail

    Eyebright

    “Orally, eyebright has been reported to cause confusion and headache (4).”

    Eyebright · Natural Medicines adverse-effect record, reported in cluster headache.

    1 source cited
    1. 4. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.

    Granisetron

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

Reported for Eyebright but not commonly for Granisetron: a stuffy or runny nose, blurred vision, confusion and swelling.

Effects for Granisetron come from the ADVERSE REACTIONS section of its FDA label; effects for Eyebright come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

How to take them

Some Granisetron Products Have a Food Rule — Eyebright Should Not Break It

At least one FDA label for a product containing Granisetron says to take it on an empty stomach. Most supplements — Eyebright included — are taken with a meal, so the easy mistake is swallowing both together at breakfast. Where that rule applies, keep Granisetron on its own and move Eyebright to a meal later in the day.

This may not be true of your version. Food instructions belong to the product, not the ingredient: two Granisetron products can carry different directions, and extended-release forms often differ from immediate-release ones. The label we read is quoted below — check the directions on your own box or bottle, or ask your pharmacist, for how to take the exact product you were given.

Recommended Dosage ( 2.2 ): The recommended dosage in adults is 10 mg administered as a single subcutaneous injection at least 30 minutes before the start of emetogenic chemotherapy on Day 1.

From the Dosage and Administration section of the FDA label we read for Granisetron — where that label names a specific product, the instruction is that product's. Read the label on DailyMed ›

A food rule is not an interaction — it is about how much of the medicine you absorb. The directions that came with your own product, and your pharmacist, outrank anything on this page.

Overlapping uses

What Granisetron Is Prescribed For, and What Eyebright Has Been Studied For

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

Granisetron is prescribed for: Granisetron is used to prevent nausea and vomiting linked to emetogenic (nausea-causing) cancer chemotherapy — including high-dose cisplatin — and radiation therapy, including total body irradiation and fractionated abdominal radiation. Granisetron hydrochloride tablets and Granisol oral solution are approved for both the chemotherapy and radiation indications. Sancuso skin patch is approved for prevention of nausea and vomiting in adults receiving moderately and/or highly emetogenic chemotherapy regimens of up to 5 consecutive days. Granisetron hydrochloride injection (intravenous) is also used to prevent and treat postoperative nausea and vomiting in adults.

Read the rest of what Granisetron is prescribed for

Sustol (subcutaneous injection) is used in combination with other anti-nausea medicines in adults specifically for the prevention of acute and delayed nausea and vomiting associated with moderately emetogenic chemotherapy or anthracycline and cyclophosphamide combination chemotherapy regimens.

Eyebright has been studied for:

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

    Eyebright for cancer

    Although there has been interest in using oral eyebright for cancer, there is insufficient reliable information about the clinical effects of eyebright 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 Granisetron on your own; if you are taking Eyebright for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

Everything else you take

See Every Supplement That Interacts With Granisetron

This page covers Eyebright only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Granisetron page lists 38 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Lithium (major), 5-htp (moderate), Acetyl-l-carnitine (moderate) and Ayahuasca (moderate).

By severity: 2 major · 25 moderate · 11 minor.

From our pharmacist’s overview on the Granisetron page

“Granisetron (Kytril, Sustol) blocks serotonin signals to stop nausea from chemotherapy and surgery, and this is a list that warrants real caution before you add a supplement to it. Most of the entries raise serotonin themselves, and stacking them on a serotonin-acting drug can push toward serotonin syndrome, a dangerous overload of tha…”

Reviewed by 2 · Jul 18, 2026

Open the Granisetron interaction page

One more smart check

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

We hold 504 real supplement products containing Eyebright, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Eyebright. Even though Eyebright itself has no known interaction with Granisetron, 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 Eyebright and Granisetron 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 Eyebright
Top half

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

29 days ago today
Medication Granisetron
Steady interest

#2,677 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 Eyebright reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Eyebright and Granisetron records this page draws on were last updated July 10, 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 Eyebright

What is Eyebright?

Eyebright
  • Eye irritation and redness
  • Conjunctivitis (pink eye)
  • Eye strain
  • Allergy and cold-related eye symptoms
  • Nasal congestion and hay fever

Eyebright is a traditional herb long used for minor eye irritation, redness, and allergy symptoms, but high-quality human studies are very limited. There is not enough reliable evidence to confirm it works, and using non-sterile herbal preparations in the eye carries a real risk of infection, so talk to your pharmacist or doctor before trying it.

Euphrasia officinalis · Orobanchaceae · Aerial parts (leaves, stems, and flowers) · Tea, eye drops, tincture, capsules, homeopathic preparations, compresses

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

Eyebright: dosing

There is no standardized or well-established dose for eyebright. Traditional use as a tea typically involves steeping the dried herb in hot water, but amounts vary widely between products and sources.If you choose to use a commercial eyebright product, follow the directions on the label and choose products from reputable manufacturers. For anything used in or near the eye, only use products that are specifically made and labeled as sterile eye preparations.

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

Read the full Eyebright monograph & all interactions
Medication

About Granisetron

What Is Granisetron Used For?

Brand names: Kytril, Sustol

Granisetron is used to prevent nausea and vomiting linked to emetogenic (nausea-causing) cancer chemotherapy — including high-dose cisplatin — and radiation therapy, including total body irradiation and fractionated abdominal radiation. Granisetron hydrochloride tablets and Granisol oral solution are approved for both the chemotherapy and radiation indications. Sancuso skin patch is approved for prevention of nausea and vomiting in adults receiving moderately and/or highly emetogenic chemotherapy regimens of up to 5 consecutive days.

Granisetron hydrochloride injection (intravenous) is also used to prevent and treat postoperative nausea and vomiting in adults. Sustol (subcutaneous injection) is used in combination with other anti-nausea medicines in adults specifically for the prevention of acute and delayed nausea and vomiting associated with moderately emetogenic chemotherapy or anthracycline and cyclophosphamide combination chemotherapy regimens.

See full Granisetron drug information
Keep checking

Other Drugs & Eyebright

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

0Major
86Moderate
0Minor
2,743No known interaction
86 Moderate 2,743 No interaction
Moderate

86 interactions

Showing 60 of 86 moderate interactions — see all 86 on the Eyebright page.

No interaction 2,743 drugs checked — show the list

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

Showing the 60 most looked-up of 2,743 medications checked with no known interaction — see the full Eyebright list.

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

Eyebright References

The 4 references that drive our Eyebright 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. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.
  2. Wichtl MW. Herbal Drugs and Phytopharmaceuticals. Ed. N.M. Bisset. Stuttgart: Medpharm GmbH Scientific Publishers, 1994.
  3. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996.
  4. Porchezhian, E., Ansari, S. H., and Shreedharan, N. K. Antihyperglycemic activity of Euphrasia officinale leaves. Fitoterapia 2000;71(5):522-526. 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 Eyebright and Granisetron Together: Common Questions

Is it safe to take Eyebright with Granisetron?
We do not list a known interaction between Eyebright and Granisetron. 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 Eyebright and Granisetron have any of the same side effects?
Yes — our sources link each of them separately to 4 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.
Should I take Eyebright and Granisetron at the same time of day?
At least one FDA label for a product containing Granisetron says to take it on an empty stomach, and supplements are usually taken with a meal — so taking them together at breakfast is the easy mistake. Where that applies, keep Granisetron on its own and move Eyebright to a meal later in the day. Food instructions belong to the product rather than the ingredient, so check the directions on your own box. This is about absorption, not an interaction.
Are Eyebright and Granisetron 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 Eyebright in each. That is a conversation for your prescriber, especially if Granisetron is being adjusted to a target.
How was the Eyebright and Granisetron combination checked?
Interactions in our licensed database are recorded against drug classes. Granisetron is filed under 3 classifications, and Eyebright has documented interactions with 1 drug class — none of Granisetron'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 Eyebright interact with any other medications?
Yes. Eyebright has 86 documented drug interactions in our database — Granisetron 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 Granisetron interact with any supplements?
Yes. Granisetron has documented interactions with 38 supplements in our database — Eyebright is not one of them. The Granisetron 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

Eyebright monograph Uses, safety profile, and every drug interaction in one place Granisetron drug information The full plain-English guide to this medication Granisetron supplement interactions Every supplement checked against Granisetron, 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 4 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Granisetron and Eyebright?

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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.