Grapenol Ingredients & Drug Interactions
What is this page for?
First and foremost: checking Grapenol against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.
Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy
Grapenol is a dietary supplement by Douglas Laboratories with 1 active ingredient. Its ingredients are commonly taken for antioxidant support, heart and circulation health, vein problems (such as varicose veins).Based on those ingredients, 910 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Red Grape seeds, skin and stems. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.
Check Your Meds Against Grapenol by Douglas Laboratories
Ask about any prescription or over-the-counter medication and we check it for interactions with Grapenol by Douglas Laboratories — and tell you which ingredient is responsible.
AI summaries are generated from our interaction database for education only — always confirm with your pharmacist. How we use AI
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HelloPharmacist Scorecard of Grapenol by Douglas Laboratories
Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.
What’s inside
Full disclosure
Grapenol contains one active ingredient: red grape seeds, skin, and stems. These grape tissues are rich in compounds called proanthocyanidins — plant chemicals that researchers believe are responsible for the extract's effects on blood vessel function and clotting.
The tablet also contains several inactive ingredients: microcrystalline cellulose, rice starch, stearic acid, silicon dioxide, and magnesium stearate. These are standard fillers and binders used to hold the tablet together.
Does it work?
Moderate evidence
The strongest evidence for Grapenol supports its use for chronic venous insufficiency — a condition where blood pools in the legs and causes swelling, heaviness, and pain. Grape seed extract is rated possibly effective for this purpose.
For other uses — chemotherapy-induced nausea and vomiting, hay fever, and weight loss — the evidence is either lacking or points toward ineffectiveness. If you're considering this supplement for a specific reason, it's worth talking through what the research actually shows for your situation.
How safe is it?
Well-documented data
Grape seed extract is generally well tolerated in studies. As a food, grapes are safe for most people.
The most common side effects reported orally are mild — abdominal pain, diarrhea, dry mouth, indigestion, headache, joint pain, and nausea — though a rare case of anaphylaxis to grape skin has been reported. For pregnancy, concentrated grape supplements and grape wine should be avoided due to limited safety data and alcohol content, though grapes as food are fine.
For breastfeeding, there isn't enough information on concentrated supplements, so talk it over with your doctor or pharmacist about whether to use it.
Meds to double-check
Moderate interaction found
Before taking Grapenol, double-check with your pharmacist or doctor if you're on blood thinners or antiplatelet drugs (like warfarin or clopidogrel) — grape extract may increase bleeding risk. Also flag any medications that depend on liver enzymes to be processed, including many antidepressants, blood pressure drugs, and heart medications.
If you take cyclosporine or midazolam, those need special attention. No interactions are documented for the inactive ingredients in this product.
The bottom line
Scorecard at a glanceFully disclosed formula with some supporting evidence for its stated purpose. Moderate medication interactions have been identified, and safety information is well characterized.
Grapenol may help with leg swelling from chronic venous insufficiency, but it interacts with a large number of medications — especially blood thinners, many enzyme-processed drugs, and a few specific medications like cyclosporine and midazolam. If you take any prescriptions, check each one against the interaction tool before starting.
Talk with your doctor or pharmacist about whether this supplement fits your individual situation and medications.
Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI
Assessment coverage: 1 of 1 active ingredient matched to our full ingredient reviews (monographs). Based on the product label dated Jul 25, 2012.
This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed
General information
Key facts about Grapenol, straight from the product label.
| Brand | Douglas Laboratories |
|---|---|
| Barcode (UPC) | 745287021200 |
| Net contents | 30 Tablet(s) |
| Market status | On market |
| Date entered into DSLD | Jul 25, 2012 |
| DSLD ID | 10887 |
| Product type | Botanical |
| Supplement form | Tablet Or Pill |
| Dietary claims / uses | All Other |
| Intended target group(s) | Adult (18 - 50 Years) |
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.
Supplement Facts
The label details for Grapenol by Douglas Laboratories, sourced from the NIH Dietary Supplement Label Database.
Supplement Facts
| Ingredient | Amount | % DV |
|---|---|---|
| Red Grape seeds, skin and stems | 50 mg | -- |
Other ingredients: Microcrystalline Cellulose, Rice Starch, Stearic Acid, Silicon Dioxide, Magnesium Stearate
Tap any ingredient to jump to its full detail below.
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
FDA Statement of Identity
A Dietary Supplement
Suggested/Recommended/Usage/Directions
Suggested Usage: As a dietary supplement, adults take 1 to 3 tablets daily with food, or as directed by physician.
Precautions
KEEP OUT OF REACH OF CHILDREN.
Tamper resistant package, do not use if outer seal is missing.
Storage
For optimal storage conditions, store in a cool, dry place. (59(0)-77(0)F/15(0)-25(0)C) (35-65% relative humidity)
General
GRP3
Brand IP Statement(s)
Grapenol(R) is a natural, full-spectrum plant extract made from grape seeds, skins, and stems - a concentrated source of oligomeric proanthocyanidins (OPC), resveratrol, and other biologically active components.
Seals/Symbols
amni(R) original formula
Is this label outdated? Report a formula or label change and our pharmacy team will review it.
Grapenol by Douglas Laboratories label
The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.
Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.
View the full label (PDF)The Ingredients in Grapenol by Douglas Laboratories
This is the 1 active ingredient this product is made of. Select it to open its full monograph.
Serving size1 Tablet(s) Dosage formTablet Or Pill Servings per container30 Amounts shown are per serving.
Red Grape seeds, skin and stems
Interacts with910 drugs
Grapes and grape products like grape seed extract contain antioxidant compounds such as resveratrol and proanthocyanidins that may support heart and b...
Red Grape seeds, skin and stems monograph & interactionsOther (inactive) ingredients: Microcrystalline Cellulose, Rice Starch, Stearic Acid, Silicon Dioxide, Magnesium Stearate. These complete the product’s ingredient list but are not active constituents.
Grapenol by Douglas Laboratories Drug Interactions
HelloPharmacist Interaction Report
Grapenol by Douglas Laboratories, which contains red grape seeds, skin, and stems, does interact with several medication types.
The most serious concern is with blood thinners and antiplatelet drugs (medications that prevent clots), where grape extract may theoretically increase bleeding risk by reducing platelet clumping.
Read the full breakdown — every affected drug type, severity by severity
Grape seed extract may also affect how your body processes a number of medications through liver enzymes. It can theoretically increase levels of drugs broken down by the CYP2D6, CYP2E1, and possibly CYP3A4 enzymes — meaning these medications could build up in your system.
The picture with CYP3A4 is murkier: some research suggests grape seed might block this enzyme, while other research hints it might speed it up. CYP1A2 substrates present a different risk: grape juice actually appears to speed up clearance of these drugs, potentially reducing their effectiveness.
Additionally, grape extract has been shown in a small study to reduce absorption of cyclosporine (an immunosuppressant), and long-term grape seed use may decrease the effects of midazolam (a sedative).
Altogether, these interactions span 911 individual medications. Because so many drugs depend on these liver enzymes, you'll want to run your exact medications through the interaction checker on this page before starting Grapenol.
Check your own medications below · Editorial policy · How we use AI
Want to check YOUR meds against Grapenol?
Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.
Go to the checkerIngredients driving the most interactions
Individual Drug Interactions
The ingredients in Grapenol interact with 910 drugs. Click any drug to see the details.
1 of the 1 ingredient in Grapenol interact with drugs. Each result below shows which ingredient is responsible. Red Grape seeds, skin and stems
AtorvastatinAtorvaliq
How Atorvastatin interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Atorvastatin interactionAtorvastatin CalciumLipitor
How Atorvastatin Calcium interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Atorvastatin Calcium interactionAtropine, Chlorpheniramine, Hyoscyamine, Phenylephrine, Phenylpropanolamine, ScopolamineAtrohist Plus, Pro Tuss, Ru-tuss, Stahist
How Atropine, Chlorpheniramine, Hyoscyamine, Phenylephrine, Phenylpropanolamine, Scopolamine interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Atropine, Chlorpheniramine, Hyoscyamine, Phenylephrine, Phenylpropanolamine, Scopolamine interactionAtropine, MeperidineAtropine, Meperidine
How Atropine, Meperidine interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 2d6 (cyp2d6) Substrates Moderate
Interaction Summary
Theoretically, grape seed extract may increase the levels of CYP2D6 substrates.
Read the full Red Grape Seeds, Skin And Stems + Atropine, Meperidine interactionAtropine, Morphine SulfateAtropine, Morphine Sulfate
How Atropine, Morphine Sulfate interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 2d6 (cyp2d6) Substrates Moderate
Interaction Summary
Theoretically, grape seed extract may increase the levels of CYP2D6 substrates.
Read the full Red Grape Seeds, Skin And Stems + Atropine, Morphine Sulfate interactionAvacopanTavneos
How Avacopan interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Avacopan interactionAvanafilStendra
How Avanafil interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Avanafil interactionAvapritinibAyvakit
How Avapritinib interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Avapritinib interactionAxitinibInlyta
How Axitinib interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Axitinib interactionAzelastine Hydrochloride, Fluticasone PropionateDymista
How Azelastine Hydrochloride, Fluticasone Propionate interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Azelastine Hydrochloride, Fluticasone Propionate interactionBazedoxifene Acetate, Conjugated EstrogensDuavee
How Bazedoxifene Acetate, Conjugated Estrogens interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Bazedoxifene Acetate, Conjugated Estrogens interactionBeclometasone DipropionateBecotide
How Beclometasone Dipropionate interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Beclometasone Dipropionate interactionBeclomethasoneBeclovent, Vanceril
How Beclomethasone interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Beclomethasone interactionBeclomethasone DipropionateQNASL, Qvar
How Beclomethasone Dipropionate interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Beclomethasone Dipropionate interactionBedaquilineSirturo
How Bedaquiline interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Bedaquiline interactionBelladonna Alkaloids, Chlorpheniramine, Phenylephrine, PhenylpropanolamineRespa ARM
How Belladonna Alkaloids, Chlorpheniramine, Phenylephrine, Phenylpropanolamine interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Belladonna Alkaloids, Chlorpheniramine, Phenylephrine, Phenylpropanolamine interactionBelladonna Alkaloids, Ergotamine Tartrate, PhenobarbitalBel Tabs, Bellamine-S, Bellaphen-S, Duragal S, Phenarbal S, Spastrin
How Belladonna Alkaloids, Ergotamine Tartrate, Phenobarbital interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Belladonna Alkaloids, Ergotamine Tartrate, Phenobarbital interactionBelladonna, Caffeine, Ergotamine, PentobarbitalMicomp PB
How Belladonna, Caffeine, Ergotamine, Pentobarbital interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates, Cytochrome P450 1a2 (cyp1a2) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Belladonna, Caffeine, Ergotamine, Pentobarbital interactionBelladonna, Ergotamine Tartrate, Phenobarbital
How Belladonna, Ergotamine Tartrate, Phenobarbital interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Belladonna, Ergotamine Tartrate, Phenobarbital interactionBelladonna, Ergotamine, PhenobarbitalBellergal-S
How Belladonna, Ergotamine, Phenobarbital interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Belladonna, Ergotamine, Phenobarbital interactionBellafoline, Caffeine, Ergotamine Tartrate, PentobarbitalCafergot PB
How Bellafoline, Caffeine, Ergotamine Tartrate, Pentobarbital interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates, Cytochrome P450 1a2 (cyp1a2) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Bellafoline, Caffeine, Ergotamine Tartrate, Pentobarbital interactionBelumosudil MesylateRezurock
How Belumosudil Mesylate interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Belumosudil Mesylate interactionBendamustineBelrapzo, Treanda, Vivimusta
How Bendamustine interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 1a2 (cyp1a2) Substrates Moderate
Interaction Summary
Theoretically, grape juice might reduce the levels of CYP1A2 substrates.
Read the full Red Grape Seeds, Skin And Stems + Bendamustine interactionBendamustine HydrochlorideBendeka
How Bendamustine Hydrochloride interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 1a2 (cyp1a2) Substrates Moderate
Interaction Summary
Theoretically, grape juice might reduce the levels of CYP1A2 substrates.
Read the full Red Grape Seeds, Skin And Stems + Bendamustine Hydrochloride interactionBenzhydrocodone, AcetaminophenApadaz
How Benzhydrocodone, Acetaminophen interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 1a2 (cyp1a2) Substrates, Cytochrome P450 3a4 (cyp3a4) Substrates +2 Moderate
Interaction Summary
Theoretically, grape juice might reduce the levels of CYP1A2 substrates.
Read the full Red Grape Seeds, Skin And Stems + Benzhydrocodone, Acetaminophen interactionBepridilVascor
How Bepridil interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Bepridil interactionBetrixabanBevyxxa
How Betrixaban interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, grape extracts may have antiplatelet effects and may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Red Grape Seeds, Skin And Stems + Betrixaban interactionBexaroteneTargretin
How Bexarotene interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Bexarotene interactionBictegravir, Emtricitabine, Tenofovir AlafenamideBiktarvy
How Bictegravir, Emtricitabine, Tenofovir Alafenamide interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 3a4 (cyp3a4) Substrates Moderate
Interaction Summary
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
Read the full Red Grape Seeds, Skin And Stems + Bictegravir, Emtricitabine, Tenofovir Alafenamide interactionBisoprololZebeta
How Bisoprolol interacts with Grapenol — through 1 ingredient. Tap an ingredient for the detail:
Red Grape Seeds, Skin And StemsCytochrome P450 2d6 (cyp2d6) Substrates Moderate
Interaction Summary
Theoretically, grape seed extract may increase the levels of CYP2D6 substrates.
Read the full Red Grape Seeds, Skin And Stems + Bisoprolol interactionEach ingredient & the kinds of drugs it affects
For each ingredient in Grapenol with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.
Red Grape seeds, skin and stems
Anticoagulant/Antiplatelet Drugs
Theoretically, grape extracts may have antiplatelet effects and may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
In vitro evidence suggests that grape extracts might decrease platelet aggregation.
Cyclosporine (Neoral, Sandimmune)
Ingesting grape juice with cyclosporine can reduce cyclosporine absorption.
A small pharmacokinetic study in healthy young adults shows that intake of purple grape juice 200 mL along with cyclosporine can decrease the absorption of cyclosporine by up to 30% when compared with water. Separate doses of grape juice and cyclosporine by at least 2 hours to avoid this interaction.
Cytochrome P450 1A2 (Cyp1A2) Substrates
Theoretically, grape juice might reduce the levels of CYP1A2 substrates.
A small pharmacokinetic study in healthy adults shows that ingestion of 200 mL of grape juice decreases phenacetin plasma levels. This is thought to be due to induction of CYP1A2.
Cytochrome P450 2D6 (Cyp2D6) Substrates
Theoretically, grape seed extract may increase the levels of CYP2D6 substrates.
In vitro evidence suggests that grape seed extract might inhibit CYP2D6 enzymes. However, this interaction has not been reported in humans.
Cytochrome P450 2E1 (Cyp2E1) Substrates
Theoretically, grape seed extract might increase the levels of CYP2E1 substrates.
In vitro and animal research suggests that grape seed proanthocyanidin extract inhibits CYP2E1 enzymes. However, this interaction has not been reported in humans.
Cytochrome P450 3A4 (Cyp3A4) Substrates
It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
In vitro evidence suggests that grape seed extract might inhibit CYP3A4 enzymes. However, evidence from animal research shows that grape seed extract may induce CYP3A4 in the liver. So far, these interactions have not been reported in humans.
Midazolam (Versed)
Theoretically, long-term intake of grape seed extract might decrease the effects of midazolam.
Animal research shows that subchronic ingestions of grape seed extract can increase the elimination of intravenous midazolam by increasing hepatic CYP3A4 activity. Single doses of grape seed extract do not appear to affect midazolam elimination.
Phenacetin
Grape juice might decrease phenacetin absorption.
A small pharmacokinetic study in healthy adults shows that ingestion of 200 mL of grape juice decreases phenacetin plasma levels. This is thought to be due to induction of cytochrome P450 1A2 (CYP1A2).
Cytochrome P450 2C9 (Cyp2C9) Substrates
It is unclear if grape juice or grape seed extract inhibits CYP2C9; research is conflicting.
In vitro evidence shows that grape seed extract or grape juice might inhibit CYP2C9 enzymes. However, a small pharmacokinetic study in healthy adults shows that drinking 8 ounces of grape juice once does not affect the clearance of flurbiprofen, a probe-drug for CYP2C9 metabolism. The effects of continued grape juice consumption are unclear.
Brand information
Manufacturer and brand details for Grapenol, from the product label.
Douglas Laboratories
See all Douglas Laboratories products- Name
- Douglas Laboratories
- City
- Pittsburgh
- State
- PA
- ZipCode
- 15205
- Web Address
- www.douglaslabs.com
Grapenol by Douglas Laboratories: Common Questions
Does Grapenol by Douglas Laboratories interact with any medications?
How can one product interact with so many drugs?
Where does this information come from?
Will Grapenol actually help with my leg swelling?
What are the most common side effects?
Can I take this if I'm pregnant or breastfeeding?
Does this supplement have any fillers?
Can I take this with my blood thinner?
Why does this interact with so many drugs?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
Not sure if Grapenol is safe with your meds?
Our pharmacists answer your medication & supplement questions — free.
Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.
The Full Monographs Behind Grapenol’s Ingredients
Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.
Sources & How We Checked
Grapenol's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.
- NIH Dietary Supplement Label Database (DSLD) — The official product label on file for this supplement.
- Natural Medicines (Therapeutic Research Center) — Evidence-graded clinical reference behind the ingredient interaction data.
Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.
The 34 references behind this product’s interaction data
Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.
Grape 34 references
- Kiesewetter H, Koscielny J, Kalus U, et al. Efficacy of orally administered extract of red vine leaf AS 195 (folia vitis viniferae) in chronic venous insufficiency (stages I-II). A randomized, double-blind, placebo-controlled trial. Arzneimittelforschung
- Xiao Dong S, Zhi Ping Z, Zhong Xiao W, et al. Possible enhancement of the first-pass metabolism of phenacetin by ingestion of grape juice in Chinese subjects. Br J Clin Pharmacol 1999;48:638-40. PubMed
- Vaswani SK, Hamilton RG, Carey RN, et al. Anaphylaxis recurrent urticaria and angioedema from grape hypersensitivity. J Allergy Clin Immunol 1998;101:S31.
- Chevallier A. The Encyclopedia of Medicinal Plants. London, UK: Dorling Kindersley, Ltd., 1996.
- Bernstein DI, Bernstein CK, Deng C, et al. Evaluation of the clinical efficacy and safety of grapeseed extract in the treatment of fall seasonal allergic rhinitis: a pilot study. Ann Allergy Asthma Immunol 2002;88:272-8.. PubMed
- Greenblatt DJ, von Moltke LL, Perloff ES, et al. Interaction of flurbiprofen with cranberry juice, grape juice, tea, and fluconazole: in vitro and clinical studies. Clin Pharmacol Ther 2006;79:125-33. PubMed
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- Ray, S. D., Parikh, H., Hickey, E., Bagchi, M., and Bagchi, D. Differential effects of IH636 grape seed proanthocyanidin extract and a DNA repair modulator 4-aminobenzamide on liver microsomal cytochrome 4502E1-dependent aniline hydroxylation. Mol Cell B PubMed
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